Monday, Feb 01, 2010 at 01:09
We don't know the answer yet Graham,
I just presumed it was a redarc charger he uses for onboard charging, and the ctek for mains charging.
Thinking about it, and reading Derek's comment it probably was an isolator.
But I don't think a defective isolator can lead to the described electrolyte boil off (which doesn't mean Dereks suggested
test is moot).
I think his second battery has suffered internal cell shortage initially.
A shorted cell would lead to overcharge of the remaining cells, taking out one after the other, by electrolyte boil off and maybe even plate deformation and associated shorts due to increasingly high charging currents.
It's almost like a chain reaction, driven by the high current from the starter battery.
The current through the defective battery is really only limited by the line fuse, and the resistance of the wiring.
Was there even a line fuse on the defective battery?
This would explain the wet spots around the dead battery (boiling over of electrolyte).
Shorted cells are usually caused by shedding of active material under deep discharge conditions, in flooded designs. The stuff then piles up at the bottom of the container until it touches the electrodes which short out permanently. A real double whammy...
Has anyone ever noticed shorted cells in AGM batteries, which shows up as reduced terminal voltage (around 2V less).
In theory shedding can't happen with AGMs because the active material is held in place firmly by tightly packed glass fibre matting between the plates.
Best regards, batterymeister
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