AggieJustin

Need a little non-diesel advice.

I have 2 electric golf carts that we use at church. They're 48V carts with 6 8V lead-acid batteries. We recently started having issues with one of them "going dead" after only a few miles of usage. The other cart performing similar duties keeps on going showing 50% battery. They have Curtis drive controllers and the controller is set with a low voltage threshold of 40V. We've plugged in the handheld programmer to watch the voltage and when the cart "goes dead". The controller shows 48-50V with no load, but the voltage drops off as soon as you depress the accelerator. Now here's the odd part, if I let the cart sit for a few hours, the batteries recover enough that I can drive it for a short time. If I park it for a couple of days (without charging), the batteries will register as "full" and I can run it again through normal operation for a few miles.

I've checked the water level and all the plates are covered. I've disconnected the batteries and load-tested them individually and they all perform the same, no single battery fails the test. When the voltage is down, I've checked for warm batteries or cables and nothing seems to be out of normal. What else can I check? It's odd that the batteries recover just from time spent sitting. These batteries were replaced early last year. When we're using it, the state of charge gauge registers as full then slowly works down to around 50% similar to the other cart. But then it will start showing signs of diminished performance and the battery gauge will drop to 10% quickly. If you don't stop pretty quick, it leaves you stranded. Hoping someone else has some ideas to look into.

Fordzilla

Doing the math, I'm wondering if there's room in the carts to wire in four 12 volt batteries, if for no other reason than testing......Ben

AggieJustin

I'd have to measure the tray, but it may fit. However, I'd still need to find 4 12Vs to fit in there. Then again, there is more science behind which configuration is better (8x6V, 6x8V, 4x12V) based on overall capacity and how far they discharge.

I just find it odd that the pack voltage drops off so much, then recovers as if nothing happens if you let it sit. I initially assumed that the water level was low, but the plates are covered. They're not filled to the top to prevent boiling over during charging. During the cold weather we had around Christmas, they performed horribly, but pretty much everything with a battery did. My problem is that I'm not able to make it through a full Sunday morning of use, where in the past the SOC gauge wouldn't get below 50% for a morning. We had the pack tested a few months ago and the dealer said there was no issue. Their only suggestion was the track usage and run time to see how much we were getting, which just tells me that's it's not as much as we need or as much as we used to get. And swapping to a new pack isn't a cheap option either.

Mexstan

Is it possible that something has gone wrong in the motor and it is suddenly drawing excessive amps? Have you measured the current drain while driving?