Lestronic Charger Question

[simple man]

I have a Lestronic II model 07850 that I'm not sure is working properly. It comes on and shuts off properly, but the finish stage voltage seems a little low (42.9 to 43.4V). I have tested the diodes (both with a DMM and also a 12V test light) and they seem fine. I noticed in the test procedure from Lester, that all the transformer voltages say "Approx". I'm wondering how much is "Approx"? Here are my findings from my charger:
Capacitor coil (cap disconnected) 463V
Secondary coil (no cap) 61.6V
Secondary coil (with cap) 82.7V

The manuals test voltages are:
Capacitor coil (cap disconnected) 480V "Approx"
Secondary coil (no cap) 61V "Approx"
Secondary coil (with cap) 88V "Approx"

From this I'm leaning towards my capacitor coil having an issue. The transformer looks fine, although a bit rusty. Could rust cause an issue? I have tried another charger on the same cart and it brings the finish charge up to 44.9V. Does anyone have an idea on this, or am I just being too critical?
Thanks all!

Edit: Is there a way to test a capacitor using a DMM? My Fluke 77 does not have a capacitance test.

[JohnnieB]

Originally Posted by simple man

I have a Lestronic II model 07850 that I'm not sure is working properly. It comes on and shuts off properly, but the finish stage voltage seems a little low (42.9 to 43.4V). I have tested the diodes (both with a DMM and also a 12V test light) and they seem fine. I noticed in the test procedure from Lester, that all the transformer voltages say "Approx". I'm wondering how much is "Approx"? Here are my findings from my charger:
Capacitor coil (cap disconnected) 463V
Secondary coil (no cap) 61.6V
Secondary coil (with cap) 82.7V

The manuals test voltages are:
Capacitor coil (cap disconnected) 480V "Approx"
Secondary coil (no cap) 61V "Approx"
Secondary coil (with cap) 88V "Approx"

From this I'm leaning towards my capacitor coil having an issue. The transformer looks fine, although a bit rusty. Could rust cause an issue? I have tried another charger on the same cart and it brings the finish charge up to 44.9V. Does anyone have an idea on this, or am I just being too critical?
Thanks all!

Edit: Is there a way to test a capacitor using a DMM? My Fluke 77 does not have a capacitance test.

Here's a service manual and some capacitor/transformer test stuff.

Looks like the voltage with the capacitor installed is a bit low. (6mfd -660VAC)
However, that should only lower the amps out, not the cutoff voltage. Should still be 45V or so, like the other charger is doing.

Since the other charger is charging the pack to about the correct On-Charge voltage, the battery sense circuit in the cart is probably pretty clean (low resistance), so there may be some dirty connections within the charger itself. Clean the Auxiliary contact in the plug and make sure all the connection between it and the control module are good.

If that doesn't do the trick, the module might have drifted out of adjustment (Age - Temperature). The cotton-picking thing is potted, so you can't adjust it and they cost an arm and leg, so you might want to consider telling it a little white lie.

Add diodes in series with the battery sense wire going to the control module. You up the cutoff voltage by 0.6V for each diode added. You want them forward biased, so the banded end goes toward negative.

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I've never had much luck checking motor start capacitors with a digital or analog multi-meter, even the ones with a capacitance scale.

[simple man]

Thanks for the great info! Looking at the values listed on the test you posted, the open cap coil voltage is somewhat higher than mine. I'll test it again while monitoring the line voltage to the house. I've noticed a quite large fluctuation on the line voltage during the day. It can go from 121.5V down to 95V! We have a shared transformer to a business next to us. I'll try running all these tests again at night and see what happens!
I appreciate the advice on using diodes to boost the final charge, and you're so right about that board costing an arm and a leg! Any particular value to use? I have a couple extra for solenoids.

[JohnnieB]

That is what I see also. Without the capacitor, the voltage is in the ballpark, but the with the capacitor installed, the boosted voltage is low, so the capacitor is out of spec. However, while that will to increase charge time, it won't change the finish voltage.

One of the nice things about the ferroresonant transformer design is that it provides some compensation for line voltage fluctuations. With a Lestronic II a 10% change in the line voltage input to the primary only produces a 1% change at the output from the secondaries. Your AC line voltage is fluctuating over 10%, but again, that should only effect charge time, not the cutoff voltage.

There are two separate, but interconnected, circuits in the charger output, the charging loop and the battery sensing circuit.

The charging loop starts at one side of the transformer secondaries, through the diodes, through one of the heavy wires in the output cable, through the charge receptacle, though a heavy wire to one of the main battery terminals, through the batteries and high current cables connecting them in series to the other main terminal, through the other heavy wire to the charge receptacle, through the other heavy wire in the output cable, through the ammeter and back to the other side of the transformer secondaries.

The battery sense circuit connects to the charging loop in two places, one the most positive and the other the most negative. In the Lestronic II, the positive voltage is sensed at the heatsink the diodes are mounted on. The negative is either connected to the outside of the negative radsok in the charge receptacle via the auxiliary contact in the plug, or at the ammeter in the two wire output configuration.

Any excessive resistance in any of the wires or cables or connections in the charging loop will cause the battery sense circuit to sense a voltage that is higher than what is actually being applied to the batteries themselves and will shut off the charger prematurely, undercharging the battery pack.

On the other hand, if a voltage drop is added to the battery sense circuit, the voltage sensed on the charge loop has to be higher by the amount of additional voltage drop added, to sense the cutoff voltage the control module is preset to.

The current flowing the battery sense circuit is very low, it is more or less a voltmeter, so just adding a resistor in series probably wouldn't work too well. However as long as silicone diode has forward bias, it will drop about 0.6V, so it is fairly easy to up the voltage on the charge loop in 0.6V increments. I used 1N4004 diodes in a Powerwise II, which is more or less a Lestronic II in a differ box, but most any diode should work.

[simple man]

Thanks, John! I think I'm going to replace the capacitor as it is original and quite rusted. I have looked on line and through our sponsors and can't believe this capacitor is almost $60!!! I just bought a start/run cap for my AC unit and it was $17 and some change! Any particular reason these caps are so high?
I'm going to try your suggestion of using a diode first, though. All the variables will then be the same for comparison. That will be an easy and quick installation and I'll let you know how it works out.

[JohnnieB]

Be sure to get the same value capacitor as the one in it. I just noticed a 3 MFD was listed for my Powerwise II rather than a 6 MFD like what is listed in the Lester manual for your charger. I thought they were clones.


Lester sells them cheaper than $60.

This should work: http://www.galco.com/buy/GE-General-Electric/27L6014
Also, you might find a 6MFD Run capacitor at you local electrical supply. (Run type is for continuous duty, Star type is for intermittent duty)

BTW: The diode is to be forward biased, so the banded end will face the negative voltage. (Opposite of the way they are installed on a solenoid)

[simple man]

Thanks for the link and I have run into the same deal with the capacity! I have this question, as I'm now confused. I have been looking caps up and they are listed as "uf", but when I look at the photo it clearly shows "mfd". These are not the same, at least it wasn't when I went to school! Are these values meant to be the same now?

[cgtech]

uf = microfarad, mfd = microfarad, same thing. at least in the electronics world "u" = micro

[JohnnieB]

In electronics, the lower case Greek letter "Mu" (μ) is shorthand for micro, but not many typewriters have "μ" on the and few people know the ASCII code for it, so "u" is often used in print.

In industrial applications MFD is used rather than μf or uf. (More correctly, they are uF and µF)They all mean 0.000001 farad.

Sometimes mF (millifarad) and MFD (microfarad) gets confused and when someone types mfd, nobody knows what it means, but most people assume they mean MFD.

P.S. Type 230 on numeric keypad while holding down Alt key and see what appears on screen.

[simple man]

Thanks again for the help! "Alt codes"- - µ - -, how about that! And yes, I'm more used to industrial applications. I did a bit of research and found out that my Lestronic II model 07850 type 36LC25-8ET definitely takes a 6MFD-660V capacitor. I also have an Accu Power Club Car charger that is made by Lester. It is a model 13800 and takes the 3MFD-660V capacitor. These two chargers look very much alike, but the transformers are constructed differently. I know that the capacitor must match the transformer, so I now see how the wrong substitutions can happen. The CC charger was coming on, but not outputing any current, so I went ahead and did the Lester tests to it, also. It definitely has a bad capacitor so I'm looking for a 3MFD cap also! Funny thing is the bad cap looks great and the old rusty one works!