From experience, we have found that in almost every case of batteries overheating / overcharging it has been down to a problem with the battery.

A lead acid battery is made up of 6 individual cells each of 2V, giving the total of 12V we are used to.

With age or damage, it is possible for one of the cells to fail.  Initial symptoms may include reduced battery performance, or when showing a good voltage (i.e. above 12.7V) the voltage rapidly dropping with even small loads.

The major problem with a battery in this state is it has now effectively become a 10V battery so will draw more current as the charge voltage is now too high and so will keep charging and eventually overheat, giving the symptoms of being “overcharged”.

If you suspect that it may be your charger rather than your battery at fault, please see the following article: My PX300 charger isn’t working correctly?