Charger Problem - Not Shutting Off

[konakid]

You guys helped me a lot with another issue, so I hope you can help again please.

OK - I've read just about everything I could before asking - so I know there are several reasons for this. And this is what I can offer in the way of info, for anyone willing to offer suggestions.

Charger - old PowerWise 36v
Batteries - (6-6v) 24 month old Interstate
Charger hums - louder when plugged into cart. Starts off around 20 amps and slowly drops to around 6 and stays there.

After several hours (6-10) I can hear bubbling in the batteries, when amps are around 6-8. I unplug and check. All are identical - around 8 1/4v - all together at around 50v (analog meter)

I have no access to parts (other than mail order) or service locations. I do have access to buy a used charger and/or some used parts and/or new batteries.

Don't know what to do next so as not to waste money - should I buy used charger, buy new circuit board for my old charger, buy new batteries, etc. (a new charger shipped to where I am in Hawaii is expensive, due to weight)

I would really appreciate any input. I will check voltages again after 90 mins.

[konakid]

Follow up:

- I found out I should wait much longer before re-checking voltages - 12 hrs. So I will do that.

But - if each battery registers 8+ volts, and total battery pack is around 50 volts, shouldn't the charger "see" that and turn off? In other words, can I assume that something in the charger is the reason it is not turning off?

[usgicollector]

For a 36v cart charger should be shutting off between 44-46 volts. So your pack is at 50 volts now, yes that would seam high.

[radioman]

I would suspect the circuit board is not sensing cut off voltage. A visual inspection might reveal a broken wire or the relay might have stuck contacts. I would try another circuit board.

[JohnnieB]

If you have a Powerwise charger like the one in the attached picture, I'm not sure if it would take a 36V pack up to 50V, even with the relay bypassed.

Could be something simple like the analog voltmeter reading high or dirty auxiliary contacts at the charge plug.

You really need a DVM (Digital Volt Meter) to work on a golf cart. Doesn't have to be an expensive one, even those sold in blister packs at auto parts stores and big discount stores will suffice.

What turns off the charger is the voltage between the red and black wires connected to the control board. (See attached schematic.)

The voltage between those two wires and the on-charge pack voltage should be identical. If not, there is a problem in the battery sense circuit.

B+ (red wire) is sensed at the heatsink inside charger and B- (black wire) is sensed by the auxiliary contact in the charger plug touching the outside of the negative radsok in the cart's charge receptacle.

[konakid]

Thanks for the replies.

And thanks JB - you're a real trooper here - last night I read a marathon thread in which you helped a guy through a couple of dozen pages of what sounded like diagnostic hell. That increased my understanding of the electrical system 10 fold - but also scared me due to the complexity and pitfalls.

I figured I would be told to get a digital meter. I will, later today. And yes, my charger is the same as the one you pictured above.

But for now (after 14 hours) - the voltages on all batteries have dropped to 7v. But what is puzzling is the pack reads 46.5v. Is the pack voltage usually more than the sum of the individual batteries?

I understand what you are saying and will do some more checking - then report back.

Edit: Oh - when I plug the charger in, it waits about 2 seconds with the amp meter at zero , then I hear a click and it jumps to around 20 amps and begins charging. Would this indicate that the relay is working properly?

[JohnnieB]

Originally Posted by konakid

Thanks for the replies.

1. And thanks JB - you're a real trooper here - last night I read a marathon thread in which you helped a guy through a couple of dozen pages of what sounded like diagnostic hell. That increased my understanding of the electrical system 10 fold - but also scared me due to the complexity and pitfalls.

2. I figured I would be told to get a digital meter. I will, later today. And yes, my charger is the same as the one you pictured above.

3. But for now (after 14 hours) - the voltages on all batteries have dropped to 7v. But what is puzzling is the pack reads 46.5v. Is the pack voltage usually more than the sum of the individual batteries?

I understand what you are saying and will do some more checking - then report back.

4. Edit: Oh - when I plug the charger in, it waits about 2 seconds with the amp meter at zero , then I hear a click and it jumps to around 20 amps and begins charging. Would this indicate that the relay is working properly?

1. The fog lifts with time.

2.

3. Both are a bit high, but analog meters aren't know for their accuracy. Granted, some are, but most aren't.

There are a couple things that could be causing the pack voltage to read different than the sum of the individual battery voltages. One is that they are most likely taken on different voltage ranges (IE: 10V and 100V), so different range multipliers (resistors) are being used. Another is that the input impedance is probably 20kΩ/V so the meter has a higher input impedance when it measures higher voltage. DVMs don't suffer either of these issues.

4. That sounds about right, maybe a little slow on the relay click. However, what makes the relay activate and what makes it deactivate are different circuits, so the control board could be half good/half bad and is turning the charger on, but isn't turning it off.

Looking forward to some voltage readings with a DVM.

[Golfdog]

Originally Posted by konakid

Follow up:

- I found out I should wait much longer before re-checking voltages - 12 hrs. So I will do that.

But - if each battery registers 8+ volts, and total battery pack is around 50 volts, shouldn't the charger "see" that and turn off? In other words, can I assume that something in the charger is the reason it is not turning off?

The Manual might help.

[konakid]

Ah - the joys of buying used equipment.....

With my new trusty $40 DVM (not many choices where I live, and not even in hundredths) here are the readings.
6.4
6.4
6.5
6.4
6.5
6.4
And 38.6v for the whole pack.

But - there are obviously issues with my charger. Please see the pics. I will scrutinize the schematics, but I can clearly see what looks like a relay on the board that is bypassed. Correct??? Is that the problem?

Also - I'm confused as to what to check for the sensing circuit. I see a red wire going to what I assume is the heat sink (the large metal plate), but the black next to it looks like it goes directly to the red wire from the 120v wall receptacle. (edit: correction in next post)

I'll read up a little more. But with the pics, I'll bet you can tell me what is going on.

[konakid]

Oops - my wires got crossed under a rag. The black wire does not go to the 120v, but to the receptacle as it should. I will now try and check the sensing circuit.

But, that bypass I see on what I assume is bypassing the relay - can't I just assume that is the problem?