The magnificent Kohler genset is not really a perfect fit for our application, and its proposed replacement is as yet nothing but a gleam in my eye. We have a couple of gasoline rope-pull generators which do yeoman's work, but I really have a liking for diesel generators. They are much more fuel-efficient, and tend to last a lot longer. They're also much better at sitting unattended, diesel fuel doesn't go bad nearly as fast as gasoline does. (Nothing beats propane for sitting, however.) There's a place in our stable for a small diesel genset, even if we have a big one for high-load periods. Unfortunately they tend to be expensive.
So I was at the local discount liquidation outlet, mostly Costco returns it seems, and they had one of their diesel generators there, wheels missing, battery out/dead, etc., for $390. (This is the same place I bought a tiller that had a thrown rod, unbeknownst to me, and by accident a gasoline generator that had a thrown rod [I pointed to the wrong one]... a place to be careful!) I'd seen these generators there before, in presumably running condition, for about $800. The lowered price...seemed...strangely...compelling. I bought it! I later found this information on the net:
Except for the paint job, the diesel generator at Costco looks like this:I pulled the following information (and the photograph above) from the website, in case the link should disappear:But instead, the Model Number is #41450 "Matrix". The manufacturer is Jiangsu Changfa Group (China). 20" wide, 25" high, 36" long. 418 cc. Weight = 346 lbs. Colors, dark gray and light biege. 4 gallons fuel = 9 hrs under load. 5000 watts constant. $1050. Electric/battery key start. I don't think the wheels are included.
Silent Type Generator Powered by Super-Light Air-Cooled 4-Stroke
Direct Injection Diesel Engine
Model Number: CF3500LN/CF5000LN (3KW/5KW)
If this generator works out I can get rid of one of the gasoline rope-pull jobs. I'm sure I can off one on friends or neighbors.
I found that an equivalent (?) expensive gasoline 5 kW generator (that Costco has right now) is rated to run for that same 9 hours, but on a 6.5 gallon tank. So the diesel is automatically 50% more efficient, right? And at partial loads it should be even better than the gasoline models.
Unless the motor is dead.
Once it had run a few times it started easily with the key. I'm sure being warm helped, as did getting all the air purged from the fuel system. The set takes a long time to spin down when turned off. There's a spring-loaded red lever behind the access hatch that applies throttle. If you hit the red-handled release lever it drops to, or below, idle and stops. There is also a red lever on top that I don't know the purpose of. It can only be accessed with the enclosure's end cover taken off.
There is no voltage output, either AC or DC. I checked the wiring and such inside the cabinet, and there were no obvious faults or burned items. The regulator is potted, so that's not very handy. There is an exposed power diode bridge, but it checks out OK. There are no specs or schematics that I can find, I'm not sure where to look next. There's an odd heat-sinked box separate from the regulator that hooks to a pair of green wires that come out of the flywheel area. Low-oil shutdown? Overspeed protection? It has an inline fuse hooked to it, which I checked. Also good. There are a lot of wires. There is a knot of three automotive relays tie-wrapped behind the control panel. Not too elegant. They're involved with the shutoff solenoid, at least. (I haven't delved into it thoroughly.)
It's a mystery. Perhaps I've just purchased a one-lung diesel motor for $400? Still not a bad deal!
When I took the big car battery off I found that the little one (36 Ah) was now taking a charge. We'll see if it recovers enough to be usable. It, not fully charged, wasn't (yet) able to fight the engine's compression enough to turn over.
...Somebody suggested the mystery red lever is a compression release. OK, but you can't operate it normally as it's hidden inside the enclosure! I tried starting it on just the little battery and it fired right up. But it's warm outside now. The battery was still drawing 4 A several hours later. It may be bad... Some hours later it was down to 2.5 A, that's a good sign.
I had a couple of small ball-bearing hub wheels lying around that actually fit on the axles, though they're large enough that they rub on the case some. They'll help with the moving around, methinks.
The red lever on top is a compression release, obviously not intended for operation in this particular installation. I pulled some tie-wrapped wiring harnesses and connectors open, one two-wire connector with red and white wires towards the generator end that had a plus label on the red wire measured low ohms, but generated no voltage. Field winding? The two green wires from the flywheel end measured low ohms, and generated 44 VAC when running. As I mentioned before, they go to a four-terminal epoxy-potted heat-sinked dingus, labeled KDK-12, by the Huifeng Electrical Machine (Changzhou) Co. Ltd. It has a fused red wire coming out of it, and the case is grounded. It has a date code of 2004.03.15 on it. I was unable to find anything on the internet. Perhaps it's a 12 V rectifier/regulator? I put it on the bench and yes, it is. Fed a variable AC voltage, the DC output comes up with it until it hits about 14.5 volts, then stabilizes. Cool. It has a 10 A fuse. (The 8 A 12 V output on the front panel comes from a separate winding on the generator end, run through that big heat-sinked bridge rectifier. It doesn't look like that circuit is shared with anything else.) When I fired up the generator again the battery voltage measured 13 V, when I connected the regulator's output the voltage started rising. It's charging, anyway. (The regulator obviously doesn't have a feedback mechanism into its generator; it probably has to burn the excess energy, making the heat sink particularly important.)
The small-gauge two-wire (red and white, red collared with a "+" label on the potted regulator side) connector to the generator end measures 17 Ω. I fed it battery power through a test light but the generator didn't generate, at least according to the incandescent lamp I had plugged into it. (Yes, the breaker was on and had continuity.) The other connector between the regulator and the generator has four mid-gauge wires, two blue and two yellow. One set, yellow, measures 0.1 Ω, the other, blue, 0.5 Ω. All of these three windings (?) appear isolated from each other. I need to figure out which of these, if any, is the field. Could there be more than one? There is another connector from the front panel that has four wires, red, black, and two white, I assume that's the power and control feed to the regulator. When running there is power between each of the other three wires and the black wire. The main generator output is large-gauge wire, and goes to a terminal block. No mystery there.
The potted regulator is in two pieces, and there are two trim pots sticking out. The tops of several standard-looking components are sticking up out of the sea of epoxy. I sure wish that was a serviceable item!
I e-mailed a request for information to the contact listed on the web site, cfpmc@public.cz.js.cn, and it bounced almost immediately:
Mailbox space not enough (space limit is 9000KB). Size of arriving mail (1KB) exceeds free space (0KB).
On the plus side the battery had stopped taking a charge, and though it was a cool morning it fired right up. I did use the compression release this time. I reinstalled the battery into its place.
Dare I use the phone number "For Information or Service" on the front? 1-888-896-6881, could it be as simple as that? This got me All-Power America, but its hours are M–F 7–4 Pacific Time. I'll have to try again tomorrow.
...I stopped by Harbor Freight and bought four solid casters, on sale for $3.50 each, to try to use as wheels. They come apart easily enough, but would they fit? The axle holes turned out to be a bit small, so I pushed the axle races out and drilled them out to 1/2". Then the wheels went on the axles easily. Bent nails through the cotter pin holes hold them on. They do tend to come partially apart because the brackets that used to hold them together are no longer there, I may have to do more later. It was good enough, however, to allow us to roll it down the ramp out of the truck. I put it in the garage. (No small feat, it's pretty full in there!) The generator is much easier to handle with wheels on it.
Somebody (thanks Scott!) sent me a link to a manual for a different generator. Not too applicable, but it appears to have the same motor (Yanmar L100?), and has some general information about generators. Wrong number of windings and type of regulator, however. Mine is obviously much more elaborate. If mine is indeed brushless as the poop sheet claims, there are diodes on the rotor that should be checked out. He also sent me a link to another, much bigger, generator that actually seems to share the exciter configuration of mine, though mine is only single-phase. This configuration has two output windings that can be connected series or parallel depending on the needs of the regulator itself, which drives the exciter's stator winding.
If this is my generator's configuration, I've already fed power to the exciter's stator winding to no effect. In which case something that spins is dead. Perhaps the rotating diodes have a problem? Let's hope so!
With the end panel removed it was also obvious that the battery is installed wrong way around. The retention strap is not centered, and is wanting to pull into the terminals. I'll try turning it around so the terminals are on the side opposite to the retention strap, but if I recall correctly the positive cable is a bit short to reach. We'll see.
When I tried the service phone number it was busy. Figures.
I tried again a little later and got through. They said that parts and service information are available, and they're sending me a parts breakdown and owner's manual. I told them I probably needed a brush pack, and they'll look it up and call back with pricing.
I checked their web site, and found what looks to be nearly the same generator. Here is what they list:
| Part # | APG3202 |
| Power | 6500 W |
| Weight | 377 lbs |
| Parts List | Not Available |
| Specs | Not Available |
| Manual | Not Available |
A lister said:
That is great news. The brushless gen heads I've seen have all been low-end. The ones with brushes last forever—as long as you replace the brushes as needed. If you are lucky, there are oil ports on the bearings. Chances are you can match up the bearings with something from Timken if and when you need to. The Chinese ST generator heads have been known to last for decades of constant use with little maintenance.Of course, I don't know if this is any kind of an 'ST' head, what I know of those they're all heavy-duty 1800 RPM jobs. My best guess is that it is not an ST head.
The field winding, interestingly enough, measures some resistance to frame ground from each terminal, it is not isolated. It might be shorted to the armature roughly halfway in the middle of its 17 Ω. I'm thinking that's not a good sign.
Disgusted, I did manage to turn the battery around. The positive cable is definitely too short, but I managed to make it reach anyway. The motor, without its mufflers, is quite loud.
I found a link referring to troubleshooting basic generators. Herein is the information, paraphrased and tidied up, for link failure insurance:
These comments are are about all Chinese ST heads.
The first step in trouble shooting is to assume nothing. Verify that your head is indeed wired as above. If you find it is wired different, you might consider making a note of how it is wired now and then wire it as above for the purpose of testing. Note: if you have a center tapped head, it will be just like the drawing above.
There is a piece of test equipment called a 'megger' that's nice to have for testing electrical appliances. The one I had experience with in the Navy had a hand crank, you'd hook it to the windings and then to the case or the ground terminal on a gen set and crank it up. This performed a high voltage test between the windings and ground. If the insulation was failing or breaking down, you'd see it. If you can get your hands on such a tester, do so. If not, use the good ol' multimeter like most of us, and proceed.
Use these test procedures at your own risk, this information is for educational purposes only! We'll assume your generator head is dry and clean and that you have grounded the head to earth ground to protect yourself. We'll also assume that it's hooked to the engine and that you can spin it up to 1800 RPM's. We also must assume that you have a good idea where 1800 RPM's is, or that you have a device like a mechanical tachometer to verify that the speed is correct. (That's a lot of assumptions!) If all this is true, proceed to Step One. Remember! the following readings were taken off the 10 kW head.
- Remove the slip ring cover and lift both sets of brushes off the slip rings. A little messing around and you'll see they stay up on their own when lifted up far enough. Make a tool out of a paper clip to pull the spring back over the top of the brush when you wish to seat them again.
Place your ohm meter across the slip rings and take a reading on the R×1 scale, you should see around 17 Ω. If true, go to Step Two. If you find a different resistance the field is suspect, consider pulling the rotor. You'll find four windings in series, inspect the solder joints and connections to the slip rings. Open the individual windings and compare them using the ohm meter. Check the field to the shaft, you should read infinite (open circuit). Once you have corrected problems here or have proven it good, go to Step Two.
- Place the meter on the R×1 scale, and place it across the field supply leads when they are removed from the diode bridge. The reading should be around 5 Ω, if true go to Step Three. If not, investigate the harmonic winding (field supply) in the stator, and replace it if bad.
- Connect the volt meter across the field supply leads. Set the meter for AC volts, 100 volt scale. Start the engine and bring the set to 1800 RPM's. You should read approx 53 volts AC, if true go to Step Four. If your reading was different, verify you are turning 1800 RPM's, if true, investigate. Stop the unit, take a 12 volt battery and 'flash' the field with the brushes lifted on one ring, put the brushes back on the rings and repeat Step Three.
- With the set stopped, reconnect the field supply leads to the diode bridge. Start the engine and verify the set is running at 1800 RPM's, connect your meter to the two screws that normally connect the two leads going to the slip rings, and note the DC voltage. It should be around 69 volts DC. If this reading is good go to Step Five. If it is off, replace the diode bridge and retest.
- If you got this far you've proved you have a correct voltage from the field supply winding, that it is being converted to DC by the diode bridge, and that you have a proper resistance in the field winding. If you have an ammeter that can accurately measure 2 amps AC place the meter in series between the field supply winding and the diode bridge terminal screw. Check all the brushes, slip rings, and connections. Start the set and run it up to 1800 RPM's. The meter should read approx 2.1 amps, if true go to Step Six. If your reading was different, verify your meter, the RPM's, and the field excitation circuit, also look at the diode bridge for a flaw. Test the diodes with the multimeter to prove them good.
- You've proved that everything is working on the excitation side. The only thing left is the output side. Continue to Step Seven.
- Verify that all test leads are removed and all the leads in the field excitation circuit are tight. Set the ohm meter on the R×1 scale, place one test lead across the output winding terminals, you should see a very low resistance, 0.02 through 0.06 Ω. If not, verify that the split windings are strapped correctly. Using the ohm meter measure between the winding and ground, the reading should be infinite. If true go to Step Eight. If there is any reading other than infinite (open) to ground, look at both windings further. Replace if necessary.
NOTE: It doesn't matter which slip ring the plus and minus sides of the rectifier are connected to, as long as you flash it in the same direction. Use a 12 volt battery, and 'flash' the field according to the plus and minus markings of the rectifier. The smart DIYer will make one of the brush rigs with a plus for quick reference later. If you take things apart and swap the leads, you will need to flash the field accordingly! Some have found the outputs of the rectifier are reversed from the drawing provided with their generator. This is not a problem as long as you note the polarity before you attempt to flash, and as long as you know that swapping these leads will kill the excitation voltage 'til you flash again correctly!
- Place your voltmeter across the output winding leads, set on a scale to read 230 volts AC. Start the engine and set at 1800 RPM's, if your reading is not close to 230 volts AC you most likely have a problem with your RPM's, your meter, or your output windings or associated leads. Get a megger and test all the windings with it. If you got here and didn't clear your problem, you are one unlucky person.
Please report any errors or omissions you might find in this text.
05/2006 Note: To date, the leading troubles in the ST design are noisy bearings and rectifier failures. The old Chinese-designed rectifier appears to be a variation of the first generation solid state rectifiers that immediately followed the ancient and bulky selenium design. This first generation unit is air cooled, made of too many parts screwed together, and is far too prone to failure. Utterpower is consulting on this, and hopefully PS heads will have better rectifiers as stock. Until then there is a retrofit kit called the ST-Mod kit that eliminates the doghouse all together and provides a far better rectifier.
As for bearings, leading causes of bearing failures are the assembler using cheap bearings, attempting to ship the bearings with little or no grease, or packing them in Yak fat instead of a proper grease. There are other problems, some assemblers will cheat the importer out of a shielded bearing on the fan side. This means the bearing and grease is open to pick up all the grit and dirt blown into it by the fan and soon you'll have a grinding compound in there working to take out that bearing in record time.
Regardless of what the importer ordered, you will only know it's right if you check. Don't have time to check? Buy something else.
I was nearby so I swung by the discount store again, and the other generator was gone. Sold, I imagine. I doubt there was anything I could have learned from it in practice, and I certainly wasn't going to buy another one, especially at 'full price'!
I also found a link to a forum entry on the theory of this low-cost regulation system. Interesting reading. Here is the most interesting information in case the link dies:
I have a diesel-driven 2-pole alternator (single-phase 230 Volt 50 Hz running at 3000 RPM. It is brushlesss and has a capacitor across the windings. What is this cap for?Interesting reading. The upshot is that the cheap resonant regulator seems to operate, similar to a constant-voltage transformer, by running in saturation and burning excess mechanical energy as heat. I would expect them to be markedly less efficient at partial load as a result.It provides the excitation and sets the frequency.
The capacitor plus the inductance of the winding form a "tank circuit"—a resonant circuit that "rings" at a particular frequency.
What happens next depends on the type of rotor you have in the alternator. (I'll describe it as if it were a squirrel cage, then delta the description for a wound-coil-diode variant.)
The ringing coil/capacitor combination produces an alternating magnetic field. If the rotor is turning at roughly the frequency of the ringing, the magnetic field from the ringing current will try to magnetize the rotor with a pair of poles. If the motor is trying to push the rotor faster than the speed that would exactly match the ringing, the rotating magnetized rotor will push against the field (which will resist it) and pump energy into the ringing (which will make it stronger).
Meanwhile, the slippage between the slightly-faster rotor and the field from the ringing coil "drags" the magnetization through the rotor. This induces a (large) current in the squirrel-cage conductors. This current maintains the field and resists its motion through the rotor.
Once started up (by a trace of residual magnetization in the rotor and its motion at or above the critical rate), the ringing and magnetization build up in an avalanche until they are limited by the "saturation" of the magnetic core material of the rotor and/or the stator. (This provides the voltage regulation.) After that point the rotation maintains the magnetization in the rotor and the ringing coil, pumping energy from the motor (by drag on the shaft) into the currents in the tank circuit and the squirrel cage to replace the energy lost to resistive heating.
With the rotor magnetized the correct amount and rotating at the correct speed, its magnetic field also generates a voltage in the output winding. Current can be pulled from there, and when it is the current resists the motion of the rotor—forcing the motor to provide the energy that drives the current into the load.
If the load pulls two much current, one of two things will happen: The rotor will slow down below the critical rotation rate to keep the tank pumped, and/or the load will start reducing the magnetic field of the rotor. Pull too much current and energy isn't pumped into the tank fast enough to replace what is lost to resistance. The ringing collapses, the rotor's magnetic field collapses, and the output voltage drops to almost zero. (This limits the output current.) Reduce the load sufficiently and the ringing will build up again.
Turning off the motor while the load is still attached MAY completely demagnitize the rotor as the generator slows down. Then you have nothing to get the process restarted again the next time you start up. You can restart things by "flashing" the rotor—driving a current through the output windings by connecting one wire to one side of a battery and striking the other wire against the other battery post. This may work if you do it when the genny is stopped (creating some residual magnetization in the rotor), and it WILL work if you do it while the motor is running (getting current going in the rotor and starting the ringing-pumping before it collapses). But use care if flashing when the motor is running, because the generator will go to full output in a fraction of a second, leaving you holding hot wires and/or with the hot wires stuck to the battery.
Squirrel cage rotors work. But they have problems. The big one is that they are lossier than they need to be (due to the slippage of the mag field through them). Another rotor type has a coil of wire to create a magnetic pole pair at a particular place in the rotor, with a diode across the end of the coil. The diode rectifies energy from harmonics and off-speed motion to get a pole started at a particular place. Then the shape of the pole pieces combined with the current keep it pinned there, without slippage, as the ringing builds its strength. Absent the slippage the excitation circuit only steals enough power to keep its coil ringing—you lose the losses that would otherwise drive the currents in the squirrel cage.
Is it [the cap] like a motor which has a cap for a start winding or aux winding?
No. In a capacitor-start or capacitor-run the capacitor is connected in series with the coil and the series pair is hung across the input power, along with the run winding.
The capacitor causes the current in the aux winding to "lead" the current in the run winding. (Ideally, it's a quarter-cycle early.) With only the run winding operating you get an alternating magnetic field. With the run and aux windings operating, you get two out-of-phase alternating fields at different angles, which amounts to a rotating field.
When the motor is stalled, a one-coil alternating field doesn't really give it a push in either direction. It will tend to sit there and buzz. Once it's spinning the rotor will be in the right position to be pulled toward the pole pieces during the high part of a cycle—but as it arrives the half-cycle is ending, and once it passes the next half-cycle builds up a field which again pulls it along. So a rotating motor will keep rotating, pretty efficiently, unless you drag it to a stop.
A capacitor-start motor only operates the aux field during motor start. A capacitor-run keeps it operating (typically at a lower strength than with a cap-start) even while the motor is running. This gives the motor a stronger and smoother pull, since it gets a strong pull at all parts of the cycle, rather than only during two of the four quarter-cycles.
The genset is rated at 2.7kVA has no engine governor as such
Fine control is not needed because once the rotation rate reaches the correct value for the resonant circuit the alternator starts resisting further speedup.
But you may find some throttle control to make the motor drive harder when the load becomes large.
The sine wave on the scope looks a bit peaky not as nice as off main grid
Probably due to the saturation of the core material.
Is there any thing I can do to give a better wave form so that the eletronics in my inverter will see it and turn battery charger on?
You can hang a capacitor across the output. (Just don't make it large enough for the OUTPUT coil to resonate at a lower frequency than the excitation coil, or your output coil will start acting as an exciter and the generator will start running at a lower frequency.)
I doubt that there is much you can do to improve the waveform, it is generally poor with that type of alternator. Anything relying on iron saturation usually has a high in-phase 3rd harmonic (peaky waveform). It should not be bad enough to confuse your battery charger.
It may be confused by the volts or frequency being out of limit. With these cheap alternators the volts are proportional to speed and if the speed is high the volts may be out of spec for the charger.
Many of these chargers are too clever to work from poor quality power sources. Also, the high reactance of many small alternators will make battery chargers perform badly (the peak of the waveform is lopped off and that is where most chargers extract their energy)
You may find it will work with a significant resistive load on the alternator such as a halogen spotlight but it will not help the fuel economy.
Yes a capacitive load causes a rise in alternator volts. With enough capacitance it will self excite.
Even well-designed alternators with AVR control of the field will lose control if too much capacitance is added. These things are generally designed for 0.8 of lagging, you never see ratings quoted for leading power factor.
And here is an interesting white paper (master's thesis) on generator voltage regulator theory. Extracts:
The auxiliary winding is designed to utilize the air-gap flux-density harmonics to supply the excitation power to the automatic voltage regulator. The auxiliary winding is wound into the stator slots together with the main winding. It is located on the top of the slot near the air gap.In this I find the first plausible explanation of why my generator might have what appears to be two separate excitation windings. One winding reacts to no-load conditions, and the other to short-circuit conditions. One is at the fundamental frequency, and the other is at the third harmonic. Together they span the range of loads from zero to shorted, and give a first-order response for regulation. In other words, the electronics of the regulator itself can be simplified if they're powered from the series combination of these two windings. If this is indeed what I have, my generator is considerably better than the run of the mill.In no-load operation, the terminal voltage of the generator is induced by an almost purely sinusoidal flux time harmonic. Clearly, this fundamental can also be utilized to obtain the excitation power in no-load operation. As the load increases, the armature current and the saturation of the machine cause higher order harmonics to arise and also these harmonics can be used in excitation. In generator short circuit, the flux is highly distorted and contains a relatively high third harmonic component which should be utilized to provide the excitation power needed in short circuit.
The auxiliary winding must be designed to utilize the chosen flux-density harmonics in different situations. The coil pitch factor determines the voltage induced by a certain flux-density harmonic. For the auxiliary winding solution to remain as simple as possible, only the minimum number of harmonics needed should be utilized. As mentioned, utilizing the fundamental and the third harmonic should be enough in no-load, load and shortcircuit operation.
For low-voltage synchronous generators, only the lowest order harmonics are to be utilized to obtain the excitation power. For the solution to remain as simple as possible, only a single-phase auxiliary winding will be used. In the following, three different winding constructions are studied considering the low-voltage synchronous generator excitation. Construction 1 presents an existing auxiliary winding solution utilized in some smaller sized synchronous generators. It only utilizes the third flux-density harmonic for excitation. In Construction 2, an attempt is made to study the principles of utilization of both the flux fundamental and the third harmonic in excitation. Being slightly different from Construction 2, Construction 3 also utilizes the fundamental and the third harmonic and guarantees better results considering the excitation also in generator short circuit.
...
Construction 3: Separate windings for the fundamental and the third harmonic. Winding H3 alone can be designed for the short-circuit excitation and the voltage in no-load and load operation can be adjusted by adding coils H1 in series without the fear of too high excitation in generator short circuit.
Depending on the voltage induced into H3 in no-load and load operation, H1 can be installed in different ways to adjust the voltage induced into the auxiliary winding. If the voltage is too low for overload excitation, H1 is wound in the same phase as H3. However, in case the voltage is too high to supply the automatic voltage regulator, it can be lowered by installing H1 so that a phase shift of 180° occurs between the voltages induced into the windings. Clearly, if H3 by itself is applicable to supply the voltage regulator in every operating state, H1 is not needed and the solution remains simpler.
Except, of course, that it is broken.
Regardless of its design sophistication, its construction seems no better than any other cheapie. And don't get me started on epoxy-potting electronics!
Anyway, all this suggests an experiment to find out if this regulation system is what I have. Procedure:
I'll need to test these hypotheses. First I suppose I should unhook the field and replace it with a dummy load, then see if it ever gets any power. If it does I could mimic what the regulator's supplying using an isolated DC source to see if it generates then.
In a way that would be nice if it did. Fix the short and fix the whole thing. But how hard would it be to fix the short, hmm? A lot easier just to blame the regulator. Easy to swap out, but not so easy to find another one.
I re-measured the field, and it's actually about 15 Ω. The short to frame is not in the middle, measurements show about a 10 Ω/5 Ω split.
I put a dummy 15 Ω load on the field output of the regulator and fired it up (the engine started instantly, even though it was quite cool this morning) using the battery charger to power the field. Loaded, and warmed up for a bit, the output of the regulator was about 15 V, which was more than I was putting into the field. (For whatever reason, the battery charger was only making 10.7 V into the field.) The regulator was pumping out more voltage, that should initiate the positive feedback required to bring the output voltage up to normal.
I checked, and the blue and yellow excitation windings are not directly hooked together. One side has megohms of resistance, the other is open. When running, one winding was putting out about 8 V, the other 4 V. A rather interesting fact is that the frequency output of both was the same according to the Fluke, which I guess isn't surprising because there shouldn't have been any third-harmonic saturation yet, and the frequency was exactly 60 Hz. (I could fiddle with the engine's speed governor and affect this.) When I hooked a 100 Ω resistor between the dummy-loaded field output of the regulator and frame ground there was no change in its output. It's not appearing that it will particularly notice the field short.
I was tricked by the Fluke, I initially thought it read 50 Hz. It's been getting worse the last couple of years, display segments have been fading out. (And unlike my usual fare, this is a unit that I bought brand new, retail.) I went to adjust the motor speed and found that it jumped to 59 Hz from '50' when I poked it. There were just too many missing segments to rely on this thing anymore. (Is that a 2 or a 3?, a 5 or a 6, etc.) Finally I'd had enough and I opened it. Fluke 83, made in USA. Far from new anymore. It is actually very easy to open up, it's very serviceable. I pulled the LCD panel off, which is held on nicely with a well-designed plastic snap clip. I cleaned the iffy-looking PCB contacts where they join the flexible foam interconnect, then put it back together. It worked perfectly again! I was on a roll so I put Goo Gone on the plastic face and used a razor blade to gently take off the green spray paint spots that had gotten on there when I was working on the big Kohler. I then used plastic polish to restore the face to a nice clarity. It's like new again, I should have done this two years ago!
To up the field voltage I hooked a 12 V battery in series with the charger, giving it about 22 VDC input. The (loaded) regulator was then putting out about 50 VDC, the main generator output got to about 95 VAC. It's starting to look like the regulator is just incapable of putting out enough field current to do the job. I wonder what a new one costs? Un-potting the existing one to repair it promises to be extremely troublesome.
I cut the last wire ties apart in the control panel, I need to trace the wiring that goes to the regulator to see what it really does.
The other unit hooks to the front panel and has a current transformer looped around the main output that it connects to. Constructed like the regulator, it has GTDK date codes of 7/06, or perhaps 1/01. Stamped on the side is "BI-1 06.07", or perhaps "B1-1". Protruding through the potting is a relay, an LED, and a ten-turn trim pot. Two small electrolytics lie just below the surface of the potting. This looks to be an overload shutdown or something like that. The potting had pulled away from the shell, the block was easily removed. The back (PCB) side was crazed, this potting material looks brittle enough that it may be possible to remove it easily. Cold (dry ice?) may be of great help.
I pulled the regulator out of its shell, but I was too energetic and managed to crack the shell. (No great loss.) There were voids in the potting, part of the PCB was exposed. There was a great deal of a coarse white granular material mixed in the black potting at the 'bottom', I don't know if this is un-melted potting material or a component thereof, or what. But this potting looks very brittle (especially where the granules are), I may be able to expose the circuitry with some care. I have this idea to use dry ice to get it very cold and brittle, and chip it off. Maybe use heat stress alternating dry ice and the heat gun. I just need to be careful not to freeze the electrolytic capacitors and ruin them!
That'd sure do it! I'll need to figure out why it blew, however. The potting material is somewhat brittle and can probably be chipped away with patience. Even without exposing the component side I should be able to do at least some circuit tracing.
...After work I stopped off and bought some dry ice. I put it in a bowl with some acetone to make a cold bath, and dipped various corners of the potted mess. I was then able to chip off chunks of it. In one session I managed to expose enough of most of the componentry to start tracing the circuit out. I did manage to break several components, that is unfortunate. They can, I hope, be replaced. In addition to the three protruding power transistors there are two signal transistors, at least a dozen diodes, and several power resistors. And the usual small handful of resistors and capacitors. The blue excitation winding feeds a heavy diode bridge, the yellow feeds a light diode bridge. Blue obviously powers the unit, yellow is apparently control. (Third-harmonic winding?)
The coarse white granules in the potting appear to be ceramic, like porcelain. Filler? Floor sweepings? Low-grade nuclear waste? Wherever its concentration was the highest was also the easiest pickin's.
Some testing showed that the small bridge's diodes are all shorted. There is a MOV across the output, and it is shorted too. It was probably the original failure, which cascaded and took out the diodes and then the trace. This is bad design, MOV's usually fail shorted, with wear, and to put one in a circuit where it can't be replaced and where there's no fuse to handle its eventual failure is just foolish.
The regulator's major mode of operation seems to be using shunt resistors to burn the excess field power.
With care and a jackknife I have been digging in what potting is left. I've exposed another two resistors and a glass-encapsulated diode. (Or perhaps a capacitor, I've seen those that look like this but I suspect a signal diode. The Fluke indicated open-circuit both ways, but I didn't try too hard. Capacitor? Burned-out diode?) I've also managed to cut a signal transistor's leg. The two signal transistors are "S8050". (Also marked "D 331".) There's still a component or two lurking in there. My best bet may be to desolder and remove selected components, especially the electrolytic capacitors, in order to gain access to more potting material to dig out. Then I have to finish tracing the schematic and come up with values for the various components. Big job!
I saw an ad on Craig's List for a substantially similar generator, brand new, but with a few more bolt-on features like a small transfer switch and a few more watts. $1900!
Because it was easy to do I popped the potting off the bottom of the other (overload?) board. It's got a 14-pin IC on it. I'm not going to try to unpot the components. It's probably not broken, nor is it critical to generation. Maybe later, if it gives me trouble.
The iron had warmed up while I did the overload board's trace-side potting removal, so I then removed the regulator's two electrolytic capacitors and the large bipolar transistor. These exposed the MOV component label (it's an 82 V unit) and the remaining potting blocks. I surfed for the big transistor, and found that there is a Chinese T2142 "Dynamo Transistor", whatever that is. No other information on it, yet. The multimeter indicates that it's more complicated than a basic transistor. I exposed the components over by the trim pot, and found what I expected. Unfortunately I cracked the glass diode! Probably no way to tell what it was now. Zener? 1N914? Capacitor, even? I pulled one of the green-dipped mylar capacitors and measured .0012 nF on the bridge. That's down in the noise. I exposed the parts under the other potting blob and found another transistor! OK, that explains the pin count. Marked "A42" and "B331". MPS-A42? That's a high-voltage level translator, rather old in fact. The PCB hole pattern was not customary, but so what. The remaining component was a resistor, as expected. The big transistors were labeled MJ10012, which is not a FET at all! They're power darlingtons, with clamping diode. (Last I was taught, it's not too kosher to parallel BJT's without small emitter degradation resistors. That's one of the reasons I assumed they were FET's.) If these are BJT's, they may be dead. I measure a dead short between C and E. This board is starting to appear to have been thoroughly fried, and half of what didn't suicide has now been killed by me. Sigh. Well, it didn't work before I started messing with it, either!
Anyway, so far the schematic I have prepared contains only the layout and the parts list. While I have a penciled schematic, I must rearrange it a few times to put it into intelligible form. There's an art to good schematic design, after all...and I'm no artist.
The mailing list guys came through, and found me a datasheet for the T2142. It is, in spite of my later fears, pretty much what I had originally figured it to be. So the circuit is still a mystery. (The T2142 may in fact be a decent replacement for the dead transistor in the 380 SL's original ignition box.)
...In the evening I did some more circuit sketches on paper, and finally got a topography that is not so confusing. One of the characteristics of a good schematic is that the 'important' circuit paths, in this case heavy current flow, are direct and straight-line. Another is that circuit components are positioned vertically roughly according to their relative DC voltages. All with a left-to-right signal flow and the use of common circuit idioms. Not an easy balancing act! I think I made about six trial layouts before hitting on one that actually made some sense and could be whipped into shape. Now I just have to put it into Illustrator.
I got some feedback from the mailing list. Craig McCluskey writes:
It seems close to the right idea overall, but has a number of quirks:He also states that the layout of the schematic is reasonable and needs no changes.It's strange that they take all the trouble to make sure Q6 gets turned off well (with Q5 AND D11), but have not provided anything to turn Q1 and Q2 off.
D10 is in a wierd location, too, since there's no way for current to flow that way.
The current in the red-green winding will always flow from red to green (unless there's induction from somewhere else), so Q6 is the wrong polarity to dump its current. Q6 will only add to the current flowing through D11.
If Q3 is turned on, Q4 (and thus Q1 and Q2) will be off and Q5 will be off. R11 will reverse bias D11 and turn Q6 on, but if current has been flowing in red-green, now having nowhere to go, it will flip the polarity on red-green so that green is positive and red is negative. This will forward bias the body diode of Q6, which will clamp the green wire at 0.7 V above the potential of C2. But why a transistor for Q6? Strange.
D12 is the correct polarity to protect Q5 from polarity reversals of the red-green winding, and D13 will clamp the base of Q6 close to the positive rail, with the current first flowing through D11 in those instances, but why go to all that bother?
Also, C4 and R6 provide POSITIVE feedback for Q3, Q4, Q1, and Q2, not negative. Is this thing supposed to oscillate and D9, et al., provide pulse-width oscillation?
On the other hand, if the red-green winding has current induced in it, so that it's a current source rather than a current sink, and has current flowing from green to red, then the polarity of D10 and Q6 make sense. But here it would be powering the circuit instead of the blue winding, the upper bridge, and C2. And when Q6 turns on, it would be shorting the output of the red-green winding (which appears to be not a good thing). Also, if D10 is conducting, D11 will be reverse biased and turning Q1 and Q2 on only pulls down on the base of Q6, and they don't need two darlingtons to do that.
Strange.
If D9 was a forward-biased signal diode R3 must have approximately 0.5 mA through it before Q3 can start conducting, that would pin D9's anode voltage (the cathode in the schematic) at around 1 V when regulation began. R4/R1's current would be approximately 0.7 mA, so R5's current would be 1.2 mA. That would make the voltage on C1 approximately 1.5 V, which seems too low.
From this I conclude that D9 is a Zener diode, of less than 12V in value. Zener diodes start at around 1.8 V in value, but I think I'll first try something like a 6 V rating. The 1N6309-20 diodes are glass, at 2.4–6.8 V in rating. 1N6319 is a 6.2 V glass Zener. 1N746A–59A are glass, at 3.3–12V in rating. 1N753A is also a 6.2 V glass Zener. There are plenty of candidates to try.
I pulled Q1 and Q2 off the board, one was shorted C-E, the other appears OK. I pulled R1 and it's a 2k trim pot, set almost exactly in the middle. The resistors, at least, seem to be marked with their values on the board's silk screen. The potting will probably make most of these illegible. Q1 and Q2 had their emitters labeled "E".
I wonder what the original failure really was? If the imbalance of Q1/Q2, due to the lack of emitter resistors, caused Q1 (let's say) to get too hot in a positive feedback cycle instead of sharing the load with Q2 and then short out, regulation would have stopped. There would be full field applied, and the generator would have gone over-voltage. This could have caused the feedback winding to over-voltage the MOV, shorting it and then burning out the diode bridge and finally the board trace. But what, then, stopped generation? There is no doubt that the thing wasn't generating anymore when I got it. D11 seems OK, there's nothing else there to block field current. Even if Q6 were shorted (which it isn't) R9 could only cut back the field current, not eliminate it. The brushes? Yes, they were low, but how could the brushes wear out if the thing wasn't generating? Who'd run it that long? They weren't burned out or anything like that.
It's a mystery!
More from Craig:
What is the power rating of R2? 30 mA through 2 k is 1.8 watts. Likewise, what is the rating of R1?I put C2 on the capacitor tester and it checks out OK. Not shorted, holds voltage, low power factor, good capacitance value.What if the MOV is intended only to clip transients and spikes? The time constant of R2 and C1 is 0.44 s, which is a long time for transients and spikes. It also gives a pole at 0.36 Hz for the feedback loop (with the yellow winding is the feedback sense winding).
If D9 was a forward-biased signal diode...which seems too low.
Not to mention that the temperature coefficient of a signal diode would make for lousy regulation.
Note also that the R1 + R4 combination can vary 3:1 in resistance, a rather wide range for adjustment.
[More than that, as R1 is actually a 2k unit.]
There are plenty of candidates to try.
Indeed there are. 6.2 V is a good starting place and is near the zero temperature coefficient point of the series of diodes.
I still wonder about Q6 and D11. If you're conducting through D11, Q6 has to be off. If Q6 is on, D11 cannot be conducting. In this case the stored energy in the red-green winding has to forward-bias the body diode of Q6.
BTW, do Q1 and Q2 have any heat sinking? I certainly hope so, particularly if they're run in the linear region.
...After work I checked, and it was running just shy of 2 A charging current. I played around with it, it puts out 120 V on one outlet, and 212 V on the other two, with no center tap. Looks like it might be rigged for putting out 3-phase voltages (120/208). That might make it interesting to try to put the whole house on. I ran a 500 W lamp off of it for a minute or so, there was no flicker at switchover. Makes sense, I think this is an 'always-on' type of unit. (It's sure loud enough to be one! Not something you'd want in your bedroom.) It drew about 14 A from the 48 V battery while running the lamp, about 4 A no-load. Plugged back in, charging current went to about 19 A for a little bit, then dropped back off to about 4 A.
I found some manuals online for a similar model of UPS. User Manual, and Installation Manual. According to these, it might not be possible to run the house on this UPS (both legs of the center-tapped 240 V) without using a rather hefty autotransformer to regenerate the center-tap. The manual says you can run loads L1-N and L1-L2, but not to run anything L2-N. Also, it's possibly only a 2 kW UPS, though 3 kVA. That's not really all that big, but it might be enough to pickle the house overnight, with care. The 4 A quiescent draw is not too attractive, but given the size of the battery bank (150 Ah@48 V) that's still some 37 hours to fully deplete the charge.
It's probably also possible to short L1 and L2 together at the house end and feed L1-N from the UPS to it. That'll feed all the house's 120 V loads, but completely starve all its 240 V loads. In fact, they'll all be rendered harmless so far as loading the UPS goes.
With it wired (though not yet insulated), I turned off the feed to the garage subpanel and hooked the UPS up instead. I was able to turn on all three banks of 1 kW fluorescent lights, but after only a few seconds they started flickering oddly then the UPS cut off due to overload. It would run two banks just fine, and I also ran up a garage door when I had only one bank on. Looks like it could work out fine, except for the fact that its 2 kW (3.1 kVA) rating is a little too small.
I then left the UPS on charge to replenish what I'd taken out.
I also put a float charger on the generator's battery.
The advertisement:
The contact:Ferrups UPS 7KVa + transfer switches and breakers!—$400 (Spokane, WA)
Reply to: sale-825965501@craigslist.org
Date: 2008-09-03, 3:37PM PDTUp for sale is this used but great UPS from Ferrups. This one supplies power for up to 7 kilovolt-amps. It uses four batteries. The control panel is removable and on a coil-cord for running tests and checking the unit. It can be used in conjunction with software on a Windows PC connected to the UPS via a DB9 serial cable.
The batteries in this unit are useable but it is recommended the buyer purchase new batteries and install them or have them installed. It is not the responsibility of the seller to provide any tech support or installation or repair services to this unit. That is all the responsibility of the buyer.
Having said that, while this unit is sold "as-is", it worked fine when last removed from service about 1 year ago. It has always been kept in a dry, clean area during operation and storage. This was a professionally used and maintained unit. Payment accepted are cashier's checks and money orders. We can discuss Paypal if need be. Please feel free to contact me (Jim) with any questions you may have.
Pictures are coming soon. Thanks! Xfer SW Front Back Opened
It is the sole responsibility of the buyer to pick up or arrange shipping of the UPS and related items included, to the destination of the buyer's choice. The seller will not ship. Local pickup is preferred.
PostingID: 825965501
- Location: Spokane, WA
- it's NOT ok to contact this poster with services or other commercial interests
Hello there! I am sorry I did not see your first email. Thanks for your interest in the UPS.Should be a nice complement to this generator, and could allow for overnight running of the house. Silent running, so to speak. (Except for the loud buzzing.) This is the big brother to the 3.1 kVA unit I already have, which is a bit too small for whole-house duty. (The no-load draw on the battery bank is too large for these FerrUPS units to be a really good whole-house overnight backup, but the price is sure right.) The battery bank I already have should be good for it to use.You can come and take a look at it if you would like.
We are 1802 North Monroe Street in the old Columbia Cycle Shop building next to McDonald's. We are also right next to the Aloha Island Grill and across Monroe Street from Shari's restaurant.
You can call me at the number below to set up a time.
Thanks!
James Kusler, Information Technology Manager
PHONE | 509.624.1613 or 800.822.4456 x.1029 | FAX | 509.624.1604
jkusler@sound-tele.com | www.sound-tele.com | www.solaxis.com
Sound Telecom is pleased to be honored as one of the
Inc. 5000 fastest-growing companies in the United States.
When I tried to power up the unit nothing happened. It's likely the batteries have gone completely dead since it was taken out of service several years ago, but as there was no way to prove that's all that's wrong I offered $200: all I was willing to risk in case it's in worse shape than claimed. (No way to prove otherwise without a research effort.) Even if it's junk the transfer switch and breaker are probably worth about that so it was a fairly safe bet. They called later and accepted my offer. They'd said that they'd had no other calls on it at all, nor bites on eBay. For that price I'm to pay for it and pick it up tomorrow. OK, will do.
...When I got the UPS home I got it out of the truck by using the hardtop hoist for Jill's 560 SL. I dropped the lid onto the car and drove it out, and backed in the truck. I laced a tow strap into a basket around the UPS (it was exactly long enough) and hooked it to the winch and lifted a bit. It was a close thing, the winch strained mightily and almost couldn't lift it. I helped by heaving up on it while I pushed the button. I then drove the truck out from under and lowered it to the floor. (I had a bit of difficulty at first when the strap's hook managed to jam the cable pulley so it could raise but not lower. I had to jack up the thing with a small floor jack and put blocks under it in the bed to release enough cable strain to get it unjammed. I then re-rigged the lifting eye to avoid the problem.)
Once down I wheeled it around into a temporary storage place behind the jacked-up 300 SDL in the center bay and took the access panel off one side. This thing is so heavy I had to use a prybar to lift the little wheels over the small lip in the concrete getting back into the garage. After blowing out the worst of the dust bunnies I found the main reason it wouldn't work is that whomever decommisioned it had done the job properly and disconnected the battery cables! (Likely as a safety matter since the unit's output wires were just bare pigtails.) Neither of the two batteries I could easily reach on the open side were flat, and I put them on charge. We'll see if there is any life left in the bank in a few days, but I'm hopeful that I can at least do some testing.
The batteries in the bottom of the cabinet are (4) Werker WKA-80J/FR 12 V 80 Ah AGM batteries. Good stuff, no sign of leakage. Replacement price on these batteries is around $100–150 each.
I also removed the other access panel and used the air compressor to really blow the dust out of the works. Cough, cough!
I found a link to a nice Battery FAQ that contains much information of interest. I've extracted a few tidbits (for protection against site evaporation):
Lifespan of Batteries
The lifespan of a deep cycle battery will vary considerably with how it is used, how it is maintained and charged, temperature, and other factors. In extreme cases, it can vary to extremes—we have seen L-16's killed in less than a year by severe overcharging, and we have a large set of surplus telephone batteries that sees only occasional (5–10 times per year) heavy service that are now over 25 years old. We have seen gelled cells destroyed in one day when overcharged with a large automotive charger. We have seen golf cart batteries destroyed without ever being used in less than a year because they were left sitting in a hot garage without being charged. Even the so-called "dry charged" batteries (where you add acid when you need them) have a shelf life of 18 months at most.Here are some typical (minimum–maximum) expectations for batteries if used in deep cycle service. There are so many variables, such as depth of discharge, maintenance, temperature, how often and how deep cycled, etc. that it is almost impossible to give a fixed number.
- Starting: 3–12 months
- Marine: 1–6 years
- Golf cart: 2–7 years
- AGM deep cycle: 4–7 years
- Gelled deep cycle: 2–5 years
- Deep cycle (L-16 type etc): 4–8 years
- Rolls-Surrette premium deep cycle: 7–15 years
- Industrial deep cycle (Crown and Rolls 4KS series): 10–20+ years
- Telephone (float): 2–20 years. These are usually special purpose "float service", but often appear on the surplus market as "deep cycle". They can vary considerably, depending on age, usage, care, and type.
- NiFe (alkaline): 5–35 years
- NiCad: 1–20 years
Battery Construction Materials
Nearly all large rechargeable batteries in common use are Lead-Acid type. (There are some NiCads in use, but for most purposes the very high initial expense, and the high expense of disposal, does not justify them). The acid is typically 30% Sulfuric acid and 70% water at full charge. NiFe (Nickel-Iron) batteries are also available—these have a very long life, but rather poor efficiency (60–70%) and the voltages are different, making it more difficult to match up with standard 12/24/48 V systems and inverters. The biggest problem with NiFe batteries is that you may have to put in 100 watts to get 70 watts of charge—they are much less efficient than Lead-Acid. NiCads are also inefficient—typically around 65%—and very expensive.Temperature Effects on Batteries
Battery capacity is reduced as temperature goes down, and increased as temperature goes up. The standard rating for batteries is at room temperature—25 °C (about 77 °F). At approximately –22 °F (–27 °C), battery Ah capacity drops to 50%. At freezing, capacity is reduced by 20%. Capacity is increased at higher temperatures—at 122 °F, battery capacity would be about 12% higher.Battery charging voltage also changes with temperature. It will vary from about 2.74 volts per cell (16.4 volts) at –40 °C to 2.3 volts per cell (13.8 volts) at 50 °C. This is why you should have temperature compensation on your charger or charge control if your batteries are outside and/or subject to wide temperature variations.
Because they have so much mass, they will change internal temperature much slower than the surrounding air temperature. A large insulated battery bank may vary as little as 10 degrees over 24 hours internally, even though the air temperature varies from 20 to 70 degrees. For this reason, external (add-on) temperature sensors should be attached to one of the POSITIVE plate terminals, and bundled up a little with some type of insulation on the terminal.
Even though battery capacity at high temperatures is higher, battery life is shortened. Battery capacity is reduced by 50% at –22 °F—but battery life increases by about 60%. Battery life is reduced at higher temperatures—for every 15 °F over 77 °F battery life is cut in half. This holds true for any type of Lead-Acid battery, whether sealed, gelled, AGM, industrial or whatever.
Cycles vs Life
A battery "cycle" is one complete discharge and recharge cycle. It is usually considered to be discharging from 100% to 20%, and then back to 100%. However, there are often ratings for other depth of discharge cycles, the most common ones are 10%, 20%, and 50%. You have to be careful when looking at ratings that list how many cycles a battery is rated for unless it also states how far down it is being discharged. For example, one of the widely advertised telephone type (float service) batteries have been advertised as having a 20-year life. If you look at the fine print, it has that rating only at 5% DOD (Depth of Discharge)—it is much less when used in an application where they are cycled deeper on a regular basis. Those same batteries are rated at less than 5 years if cycled to 50%.Battery life is directly related to how deep the battery is cycled each time. If a battery is discharged to 50% every day, it will last about twice as long as if it is cycled to 80% DOD. If cycled only 10% DOD, it will last about 5 times as long as one cycled to 50%. The most practical number to use is 50% DOD on a regular basis. This does NOT mean you cannot go to 80% once in a while. It's just that when designing a system when you have some idea of the loads, you should figure on an average DOD of around 50% for the best storage vs cost factor. Also, there is an upper limit—a battery that is continually cycled 5% or less will usually not last as long as one cycled down 10%. This happens because at very shallow cycles, the Lead Dioxide tends to build up in clumps on the the positive plates rather in an even film.
Battery Voltages
All Lead-Acid batteries supply about 2.14 volts per cell (12.6 to 12.8 for a 12 volt battery) when fully charged. Batteries that are stored for long periods will eventually lose all their charge. This "leakage" or self discharge varies considerably with battery type, age, & temperature. It can range from about 1% to 15% per month. Generally, new AGM batteries have the lowest, and old industrial (Lead-Antimony plates) are the highest. In systems that are continually connected to some type charging source, whether it is solar, wind, or an AC powered charger this is seldom a problem. However, one of the biggest killers of batteries is sitting stored in a partly discharged state for a few months. A "float" charge should be maintained on the batteries even if they are not used (or, especially if they are not used). Even most "dry charged" batteries (those sold without electrolyte so they can be shipped more easily, with acid added later) will deteriorate over time. Max storage life on those is about 2–3 years.Batteries self-discharge faster at higher temperatures. Lifespan can also be seriously reduced at higher temperatures—most manufacturers state this as a 50% loss in life for every 15 °F over a 77 °F cell temperature. Lifespan is increased at the same rate if below 77 degrees, but capacity is reduced.
No-load typical voltages vs state of charge
(figured at 10.5 volts = fully discharged, and 77 °F). Voltages are for a 12 volt battery system. For 24 volt systems multiply by 2, for 48 volt system, multiply by 4. VPC is the volts per individual cell—if you measure more than a 0.2 volt difference between each cell you need to equalize, or your batteries are going bad, or they may be sulfated. These voltages are for batteries that have been at rest for 3 hours or more. Batteries that are being charged will be higher—the voltages while under charge will not tell you anything, you have to let the battery sit for a while. For longest life batteries should stay at 40% charge or higher. Occasional dips into the 20–30% range are not harmful, but continual discharges to those levels will shorten battery life considerably.
State of
Charge12 Volt
batteryVolts/
Cell100% 12.7 2.12 90% 12.5 2.08 80% 12.42 2.07 70% 12.32 2.05 60% 12.20 2.03 50% 12.06 2.01 40% 11.9 1.98 30% 11.75 1.96 20% 11.58 1.93 10% 11.31 1.89 0 10.5 1.75 It is important to realize that voltage measurements are only approximate. The best determination is to measure the specific gravity, but in many batteries this is difficult or impossible. Note the large voltage drop in the last 10%.
Battery charging takes place in 3 basic stages: Bulk, Absorption, and Float.
Bulk Charge: Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80–90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no "correct" voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take.Absorption Charge: Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.2 to 15.5 volts.
Float Charge: After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. Note that for long term float service, such as backup power systems that are seldom discharged, the float voltage should be around 13.02 to 13.20 volts.
Battery Charging Voltages and Currents
Most flooded batteries should be charged at no more than the "C/8" rate for any sustained period. "C/8" is the battery capacity at the 20-hour rate divided by 8. For a 220 Ah battery, this would equal 26 Amps. Gelled cells should be charged at no more than the C/20 rate, or 5% of their amp-hour capacity.Charging at 15.5 volts will give you a 100% charge on Lead-Acid batteries. Once the charging voltage reaches 2.583 volts per cell, charging should stop or be reduced to a trickle charge. Note that flooded batteries must bubble (gas) somewhat to ensure a full charge, and to mix the electrolyte. Float voltage for Lead-Acid batteries should be about 2.15 to 2.23 volts per cell, or about 12.9–13.4 volts for a 12 volt battery. At higher temperatures (over 85 °F) this should be reduced to about 2.10 volts per cell.
Battery Aging
In situations where multiple batteries are connected in series, parallel or series/parallel, replacement batteries should be the same size, type and manufacturer (if possible). Age and usage level should be the same as the companion batteries. Do not put a new battery in a pack which is more than 6 months old or has more than 75 cycles. Either replace with all new or use a good used battery. For long life batteries, such as the Surrette and Crown, you can have up to a one year age difference.When using a small solar panel to keep a float (maintenance) charge on a battery (without using a charge controller), choose a panel that will give a maximum output of about 1/300th to 1/1000th of the amp-hour capacity. For a pair of golf cart batteries that would be about a 1 to 5 watt panel—the smaller panel if you get 5 or more hours of sun per day, the larger one for those long cloudy winter days in the Northeast.
Conclusions? I may well be using too high a float charge on the Kohler genset's starting battery. This site essentially states that it should be at most 26.8 V, whereas I've got it set at 27.8 V. (I measured it at 27.4 V, but I did crank the thing over for some exercise less than 24 hours earlier.)
...In the late afternoon the second battery was still drawing 2 A and it was pretty warm and making bubbling sounds. I disconnected the charger and put it on the third battery. I moved the trickle charger to the fourth battery.
...Five hours later #3 was down to about 3 A.
...By early afternoon #4 was warm and bubbling, so I took it off charge. Ready to try firing it up, I suppose. I measured #3's rested open-circuit voltage at 13.23 V.
The fluorescent display in the control panel is very weak and ghosty. It is not good, barely usable in fact. I wonder if it is repairable?
...After work I tried the brightness setting of the panel, it's already at its highest. I also dug up another User Guide for the series, it looks more like this unit. Also acquired was the Tip 503 guide. I put the unit back on to charge. (According to this manual the unit only has a 5 A battery charger; heavier chargers are optional. [I believe the 3.1 kVa unit has a 20 A charger.] No way a puny 5 A charger will serve for my proposed usage pattern. The UPS itself only showed a 5 A charge, as did my clip-on DC ammeter, so I guess I should believe the manual.)
I hand-drilled out the four heat-staked corners of the control panel, and removed the circuit board. Fairly basic, and largely surface-mount. Date codes in the 1996 timeframe. It has a LM3405T 5 V voltage regulator, a 1488/1489 RS-232 pair, a NEC D78C14GF-R75 processor clocked by a 14.7456 MHz crystal, a 93C46 64×16-bit serial EEPROM, ON Semi's 34064 reset generator, one CMOS 14024B 7-bit ripple counter, one MC1413D high-voltage NPN Darlington (7) transistor array, a TC1428CPA 1.2 A Dual High-Speed MOSFET Drivers 8-pin DIP, and a Mitsubishi M66004FP 16-digit 5×7-segment VFD controller. Plus the usual handful of R/C/D components. Oh, and a VFD display and a rubber membrane keyboard. Near as I can tell, the VFD's 37 Ω filament is AC-coupled and is getting fed around 0.2 V. There is a 1N4753A 1 W 36 V Zener diode that indeed has some 36 V across it, looks like it's being built with a voltage multiplier chain driven by the TC1428 clocked at 200 kHz. That's right in the ballpark for what the M66004 wants for grid drive. The filament voltage, though, is highly suspect. It looks like it might come out of the same voltage multiplier chain that the high voltage does.
The 78C10, 78C11,and 78C14 single chip 8-bit microcomputers integrate a 16-bit ALU, 4k ROM, 256-byte RAM, an 8-channel ADC, 16-bit timer/event counter, 2 8-bit timers, a USART and much more.The 7810 is ROMless
The 7811 has 4K ROM
the 7814 has 16K ROM
A little surfing shows that it is customary for the two filament pins to be biased above ground so that the tube cuts off when it should, and that the net filament voltage should be around 3 V. (Your basic triode, in effect.) Well, we're seeing heavy ghosting and no brightness to speak of, so I'd lay the blame squarely on the filament drive. And that, at least, is exposed circuitry. This should be repairable, the filament itself is good.
I powered up the board on the bench, I clipped 12 V right across the input filter capacitor and the display powered up 'normally'. That's a whole lot better working environment than crouched over the opened-up FerrUPS out in the garage.
I did some more surfing, and found an Application Note for National's LM9022 VFD filament driver chip. This shows a typical circuit that vaguely resembles what's on this board, with (probably) the TC1428 taking the place of the LM9022. Everything else I could find assumed a center-tapped power transformer.
While I did all this I let the UPS charge its batteries. By the time I gave up for the night it had shut off the charging circuit, so I powered it down and put away the big 240 V extension cord. To bed!
The M66004 requires the –36 V drive (VP) in order to turn off the digit grids. (The segment anodes and grids are switched between this and +5 V, giving a proper net voltage for the tube.) The common-mode filament voltage needs to be somewhat less negative than VP or ghosting will occur. I need to look there next. I think I need to trace out the schematic of the voltage inverter and filament drive circuitry, it all keeps pointing back to there.
...After work I checked the drive levels out of the M66004, and the anode and grid levels both drop to within a volt of the VP negative supply voltage (–36 V). According to the 'scope, the balanced square-wave filament drive is approximately symmetrical around this voltage, let's call it –30 V to –40 V, which is not adequate to prevent ghosting, its average level needs to be several volts above the negative supply. I created a filament drive schematic by tracing the circuit. (This is tedious: it doesn't take all that long to trace out the connections, but getting it drawn with a meaningful topography usually takes several tries.)
Having seen the circuit for what it is now, I still don't see how the filament bias is really accomplished. Looks to me like it's missing a resistor or two, yet there is no sign of one.
I spent some time making a
partial schematic, in Illustrator, PostScript, PDF, and GIF
formats. Thinking about the circuit I've decided that it's a
non-traditional voltage quadrupler, inverting. That gives you around
–36 V from its +12 V drive. Being non-traditional in form
(not a Greinacher/Cockroft-Walton ladder) means that the diodes and
capacitors are exposed to greater voltages than in a ladder, but
because this is a relatively low voltage circuit (as opposed to
multi-kilovolts) that is not an issue. I suspect that this form, with
proportionally greater drive voltages on the capacitors, results in
more efficient current production or something.
Anyway, the drawn circuit basically has three parts: the zener-regulated inverting voltage quadrupler, the AC filament drive, and the negative voltage (–15 V) supply for the RS-232 driver. The filament drive is what is interesting, it's taking the 12 V square-wave drive from U6 and coupling it through R8/C10 and R6/C9 to the 37 Ω filament. This results in a sufficient AC current flow through the filament to enable it to emit electrons. However, the filament as a whole has to be at a high negative potential or those elecrons won't actually be emitted. Optimally it's a few volts positive from the negative rail, which is what the anodes and grids are switched to while scanning. R5 and R7 together bias the AC-coupled filament to VP. Unfortunately I don't see how this bias stays above the negative rail, which results in ghosting. On the oscilloscope the AC filament drive is centered around the negative rail voltage, which means it's not positive enough for good operation.
Enter the modifications.
Adding Ra and Rb to the circuit lifts the average filament potential
(referenced to ground) a bit by pulling it towards ground/12 V,
eliminating the ghosting. This lessens the cathode-to-anode voltage,
however, resulting in less current flow in the tube and a dimmer
display. By adding Ca and Cb in the circuit the filament current is
pumped up a bit, restoring brightness.
The end result is a more usable display, but one that's still relatively cruddy looking. There's probably another failure mechanism at work, perhaps the VFD tube itself is wearing out. (I wonder if the normal expected anode operating current was supposed to pull the filament potential up a bit against its bias resistors? If the tube is now conducting less than normal that would shift the cathode potential down, causing the ghosting problem.) Regardless, it looks like these modifications will at least allow the unit to be used again.
I snapped the control panel back together again and put it on the UPS. Now it is indeed usable again!
The carburetor float in the little 1600 W Coleman had stuck and the thing flooded. (Good thing my boss didn't take me up on my loan offer during last winter's power outage!) I had to remove the carburetor bowl and clean off a little bit of varnish that'd built up on the hinge. After I put it back together it ran again without vomiting fuel all over the place. It still had an oscillating governor, which I've tamed in the past by putting on the choke a bit, so I opened up the needle valve a half turn or so to richen the mixture and dampen the oscillation. All three generators then ran fine at that point, so I turned off their fuel cocks and let them run dry. Ready for winter, I guess.
What I really need to do is get that voltage regulator repaired on the diesel.
The VR might be a clone of a Honda unit. FWIW, I've gotten useful troubleshooting info on potted VR's in the past by searching patents.....searching for 'AVR' or 'regulator', with 'Honda' or the like in the assignee field......heck, try Changfa too, for that matter.....some mfg's name might bring up a patent with a schematic that's very close to what you have.I have successfully measured 'broken' glass zeners in the past....by fixturing the end with the lead that the chip is brazed to....and probing the top-surface with a needle chucked up in a precision XY stage. Without going to the (great) trouble to make all this work under the microscope, I simply probed various spots....some gave a 'short' to the lead the chip's brazed to....which I interpreted as the needle hitting the substrate....but most spots gave a voltage that made sense (I used a metered bench-supply set to 40 V and current-limiting set down to 10 mA or so)....which I interpreted as my needle landing on the metallization for the top lead. Of course, if the chip itself was shattered during the breakage, then yer SOL.
