-15 Code on 2000 Gem

Hi all,
Just registered and did a long search… Found out 15 code means low voltage and charger wont charge.
Heres my prob.
Just bought the Gem
Just installed new batts today. (made all new cables as well)
Plug it in and get no charge light but checking with volt meter the charger is charging. Goes from about 74 volts at the motor controller to like 80 volts or something like that.
Whenever master switch turned on I get a constant buzz from busser and a -15 code.
Turn master off buzzer eventually stops.
Plug charger in and buzzer is on again even with the master switch still turned off.
The car wont drive.

Hopefully somebody else knows the problem.:help:
Thanks in advance for any help you can give me.

Nothing should work with the master switch open. Has the wiring been altered? The buzzer indicates a parking brake released with the key turned off or that reverse is selected. The buzzer should be off with the parking brake on and the selector not in reverse. You should hear the main relay close whenever the parking brake is released. The small safety switch mounted on the parking brake lever often comes out of adjustment.