charging problem

[parsonpt]

I have an old Total Charger with a timer. After I plug it in, it will run for a few minutes and turn off. It will repeat this after I replug it in again. The battery voltage is above 36 volts and the relay appears to close to start up the charger. The voltage during the brief charging climbs to 39. The charging amps on the dial are about 18. I have used a 12 volt charger to recharge two at a time.
What are the possible causes?

 

[HotRodCarts]

If the batteries and the cables are all good I'd say it's a problem with the timer in the charger.

 

[parsonpt]

what makes the charger turn off. is it that the voltage output gets too high, or the charging current gets too high. neither of these seem to be an issue.

what if one of the batteries is bad. what is it about this bad battery that the charger senses that makes it cut off?

I am trying to understand how the charger works. it does not seem to be just a simple output voltage cutoff.

 

[HotRodCarts]

Does the charger have a manual timer or is it a automatic timer? The automatic charger uses the voltage as a guide for when to shut off. I've seen both the automatic and the manual chargers turn on and off if there's a short in a cell bad cable connection etc. Or it could be the timer itself or the relay which is on the timer board.