48V drops to 29V - stutters

mikec35

I have a 1997 48v Club Car with 2 year old batteries. I checked each batteries voltage and they range from 8.468 to 8.531 volts (after sitting for a week off the charger.) Across all of the batteries I get 50.99 volts. I checked the specific gravity of each battery and all cells check out great. I depress the accelerator and it jumps but won't hardly move. I put my meter across all batteries while trying to drive it under a load and I got 29 volts. I can't check each battery under a load as I can't get the cart rolling. All battery posts are clean and I have all new 4 gauge battery wires. I did not replace the hot wire from the solenoid to the battery or the ground wire from the controller to the negative post on the battery - I cleaned the terminals on those 2 wires (they weren't bad.). So, aside from checking/cleaning all my connections on the solenoid and motor and possibly replacing the 2 wires I cleaned what else should I look for?

BGW

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Raystar57

I would look at the solenoid first.
Worn contacts can cause a voltage drop like that.
It still could be the two cables.
I would then look into the motor brushes next.

Golf cart guy

Its not the solenoid, but I would check the batteries under a load first

Raystar57

A load test is a good idea.
Since you can't get the cart to move to use it as a load then you would have to obtain a load tester
or take the batteries/cart somewhere to have them checked.
I wish auto stores would do a loaner on these but usually they don't.
What make and type of batteries are these?

Cable terminals can look good but still be bad inside the crimp.

Solenoid may be ok; has it ever been replaced?
If it's stock 1997 then it could be on it's way out.

That 20V drop is a lot and some resistance in the current path is causing it.

Trying to not look at controller at this point as other things need to be checked out first.

rib33024

Check each battery the same way you checked the whole pack. And see which battery or batteries are dropping out.

Raystar57

Good point Rib! I couldn't see the forest through the trees!

mikec35

Thanks for the replies. I'll check each battery under a load the same way I did the pack and will report back next weekend. I figured since each battery passed the specific gravity gravity test they would be ok. Can one of those 6v12v load testers be used on an 8v battery as well?

ThreeCW

I think that "rib" is on the right track.

I had a similar case where pack voltage and individual static voltage was good but under an applied load (trying to move the cart), one battery was dropping out (internal shorting ??). After attempting to move the cart, I checked the individual battery voltages and the "bad battery" voltage had dropped from 6.4v to about 4 volts (if I recall correctly). I suspect that if I had checked the "bad battery" voltage under applied load (trying to move the cart), that the voltage would have been even less. I replaced the bad battery and all was well.

If the battery "applied load test" checks out successfully, the next easiest thing to do would be to check the resistance of each of the high amperage cables on your cart. The resistance of each cable should be under 1 ohm or so.

Regards, 3CW

mikec35

I found 2 batteries that dropped to about 3 volts under a load while trying to drive the cart, the other 4 batteries are staying right at about 7.9 to 8 volts. This is strange since I tested the batteries after sitting for a week and they all test about 8.4-8.5 volts static and I checked every cell in the batteries specific gravity and all were perfect. I have new cables but am wondering if I have a couple of bad new cables? How do you test the cables? Thanks

ThreeCW

Test each high amperage cable individually using your multimeter on the resistance function (ohms).
Leave the cables installed on the batteries / solenoid / FR contactor / motor / controller.
Include the connection at each end of each INDIVIDUAL cable if possible (battery post, solenoid post, FR contactor, motor, controller). If you get a high reading (more than 1 or 2 ohms), test again from cable connector to cable connector (as the connection might be the cause of your resistance).

As a minimum, it looks like you have two failed batteries.

What year are your batteries (check the date code)? What make?