Charger Problem - Not Shutting Off

[konakid]

OK - so I checked the sensing circuit and it appears to transmit the pack voltage to the board.

I'm guessing my next step is to replace the board. But I would like to hook up the relay, just to see what will happen. As mentioned. I hear a click of some kind after plugging it into the cart.

But - how do I know which terminals on the relay to connect the wires to? Does it matter? I'll need to know this even if I purchase a new board.

[konakid]

I got impatient so I took a risk.

I routed the wiring back through the relay. It clicked when plugged into the cart (no AC), and the cart is now charging when AC is applied. I may get lucky here. I’m hoping that maybe the old owner bypassed the relay because of some faulty/old batteries - and when he bought new ones, forgot to put things back as they should be.

Does that make any sense? From what I have learned here, if the charger wouldn't turn off, the solution would not be to bypass the relay. Right? The only reason to bypass the relay is if it wouldn't turn on. Right?

But - too early to count my chickens - the problem was that it wouldn’t turn off. But the amps are going down as it charges, the sensing circuit appeared to be working - so in a few hours I should know the answer. Right?

Fingers Crossed Emoticon here.

[radioman]

Looks like you found the problem.

[konakid]

Originally Posted by radioman

Looks like you found the problem.

Thanks for everyone's help - yes I did.

Just went to check after about 4 hours and the charger was off. It was already close to a full charge when I started, and the amp meter had dropped to 5 amps after about 45 mins - so it probably turned off a while ago.

We will never know why a perfectly good relay was bypassed, but my explanation above makes the most sense to me. I hope you would all agree since that would mean I understand what was going on.

This is the second situation where you guys saved me a lot of money, and got me up and running while teaching me some things I can use in the future.

Thanks a million.

[JohnnieB]

I got shanghaied by SWMBO (She Who Must Be Obeyed) yesterday afternoon, but it sounds like you figured it out and fixed it.

Your reasoning about why the previous owner bypassed the relay is most likely correct. It is the cart's battery pack the closes the relay initially.

About your question: "But the amps are going down as it charges, the sensing circuit appeared to be working - so in a few hours I should know the answer. Right?"

Sounds like you share the widely spread misconception that the "Control" board controls the charger. All the control board is, is a semi-smart On/Off switch. If the pack voltage is high enough, it turns on the charger, when the on-charge voltage climbs to a preset voltage in the 44V to 46V range it shuts off the charger and if the pack voltage doesn't not reach the preset voltage in about 16 hours, it shuts off the charger.

The charger consists of a ferroresonant transformer and capacitor along with a pair of diodes. The transformer and capacitor react to the on-charge voltage to limit the amps to about 20A initially and then tapers off as the on-charge voltage climbs to a amp rate that won't cook the battery.

The earliest versions of this type charger (that I know of) had a mechanical timer. Attached are three examples.

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[konakid]

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