If you hear any bubbling of the electrolyte, you are getting gassing (which is explosive!). You might want disconnect the charger for 30 minutes if you hear rapid bubbling or if the case on the top is quite warm. If the battery top case is quite warm definitely back off or you will shorten the life of the battery. If it is so hot that you want to pull your fingers off after touching it, disconnect your charger quickly and wait 30+ minutes before reconnecting it.
Make sure that you add distilled water (don't flood it) if the electrolyte level is low and near the plates, and check the level periodically during the charging process.
The generation of heat and bubbling depends on the condition of the battery and how badly it has been discharged. A deeply discharged or deteriorated battery may got hot quicker than a good, slightly discharged one.
Make sure that you add distilled water (don't flood it) if the electrolyte level is low and near the plates, and check the level periodically during the charging process.
The generation of heat and bubbling depends on the condition of the battery and how badly it has been discharged. A deeply discharged or deteriorated battery may got hot quicker than a good, slightly discharged one.