Hot over charging battery problem

We have 2 house batteries with a solar panel charger to keep things topped up when we are away. Recently one of the batteries is over charging. Just changed the charge controller but still same problem. Any ideas please

Shorted cell ?? If your battery is getting hot your charging system must be rather OTT for keeping the batteries topped up.

Check the volts on the suspect battery after it has stood for 24 hours disconnected with no charge or load. If its a shorted cell you will only see around 10.5 volts
 
I've changed battery. The disconnected battery recovered. But the replacement is now over heating. Solar panel covered, no charge and still hot.

Odd. Can you confirm that the "2 house batteries" were connected as a bank in parallel with each other. That's what I (and Vic, I imagine) presumed to be the case.
What's the status of the battery you haven't replaced (temperature whilst charging, rested voltage)?
 
Had a problem with one of my two batteries (connected in parallel) overheating. After much mucking about with the charging system changed the overheating battery (it could not hold it's voltage after an hour rest) as the other seemed to be holding it's voltage okay. Within a couple of days the other (old) battery also started over heating. Changed that one to and no problems in the 12 months since
 
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