Batteries Overcharging Badly

[cmillsap]

Mike,

David knows much more than I do. I think a process of elimination may help us diagnose here. If you could answer these questions, it may help to determine the problem.

1) The initial problem was the chassis batteries were not being charged.
a) Was the coach plugged in and sitting without the Aux Bat switch on?
b) Did the coach batteries charge up after running the engine?
c) Did you notice what the inverters/chargers were reading while the bus was plugged in to shore power before you took the bus to be repaired?

2) The repairs included new chassis batteries, new alternator, new voltage regulator, and a solenoid (?). During the process, 4 of the 6 house batteries were changed after testing them for load strength.
a) After installing the new batteries; did they check to see if the inverter/chargers would charge the batteries properly when plugged into 120V shore power or did they run the generator to supply 120v power to the inverter/chargers?

b) If they did either, were the batteries being charged properly by the inverter/chargers? Were they not boiling over? Was 13V showing on the volt meters on the dash and were the inverter/charger remote readouts showing a particular stage of charging?

3) The house batteries started gassing as you drove from the repair facility. Also, the DC voltage gages started to show 14V.
The questions now are what started the new problem of battery boil?
a) Is the new alternator current set too high at the voltage regulator causing the batteries to boil?
b) Is there a bad (shorted) cell in one of the new batteries?

Since the engine alternator and the voltage regulator were replaced and your batteries are boiling over when being charged by the new engine alternator and voltage regulator, I would suspect (as a possible cause) that the new voltage regulator is supplying too high voltage. It could be bad or adjusted improperly. If they had checked that the batteries were charging properly through the inverter/chargers, then we could have eliminated the bad batteries as the cause. But if they didn’t do that, we can not eliminate a bad cell in one of the new batteries.

Also, replacing less than all of the batteries in a tied group is not a good practice, especially if the group is aged to the point that some of them must be replaced. Once you solve the problem, I would also suggest that the 6 house batteries should be the same age and all alike.
Chuck