Battery Drain

[In Utopia]

Noticed I'm not getting the milage out of my year old 36 volt system.
With my very limited understanding of electricity I checked voltage across the pack got 39 volts.
Then checked from the + post to various points on the frame with the - lead on the meter and got a reading of 28.4 volts.
I always thought the electrical system was totally isolated from the frame.
If this is the case it would appear that I have a place in the positive where it's touching something.
Am I correct in this assumption? If so any suggestions as where to start looking?

[Bama Brad]

You are correct. Need to check all wiring to see if a wire has rubbed raw.

[JohnnieB]

Originally Posted by In Utopia

Noticed I'm not getting the milage out of my year old 36 volt system.
With my very limited understanding of electricity I checked voltage across the pack got 39 volts.
Then checked from the + post to various points on the frame with the - lead on the meter and got a reading of 28.4 volts.
1. I always thought the electrical system was totally isolated from the frame.
2. If this is the case it would appear that I have a place in the positive where it's touching something.
Am I correct in this assumption? If so any suggestions as where to start looking?

1. Yes, but there are no perfect insulators, so there will always be some leakage current and with a sensitive enough voltmeter, some voltage will be measured.

2.If the positive was actually touching, you'd get the same voltage as at the positive terminal, so either the touching is withing the pack, or it is due to leakage current.

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My guess it is just leakage current. The voltage is roughly 3/4 the pack voltage, so the resistance between the frame and battery terminals is roughly three times the input impedance of the voltmeter you're using to measure the voltage.

Cleaning the batteries with a baking soda solution will likely reduce, but not eliminate it.

[In Utopia]

Did a good baking soda wash with it, and it had no effect on the problem.
If I get time tomorrow, I’m going to check the voltage on each battery separately and see if somethings wrong there. I did notice some extra discharge from the batteries on the cement floor which maybe just water that dripped down after I washed the batteries, don’t know what that means but I’ll probably end up pulling each battery out and inspecting it also.


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[JohnnieB]

Have a 10kΩ (or so) resistor connected across the voltmeter leads when you measure the voltage on the frame.

If it goes away, or drops way down, it was just a phantom voltage caused by leakage current.

[In Utopia]

Checked it twice today without a resistor, 9 volts each time.
Go figure.
Had a neighbor check his cart the way I did, he came up with 9 volts also, so I guess I'm good.