I've got new (18 month old) FLA house batteries. 2 x 6v. One has started boiling it's cells, so twice now we've found the cells 'dry' (being the tops of the plates are out of the liquid). The other battery has taken water, but has never dried a cell (3 cells each battery).
They are Exide 220 amp hrs.
Is this a sign the battery is stuffed, or a possible over charging issues? They are still within warranty.
We have 2 x 90 watt solar panels going through an MPPT controller. I was very careful in setting up the controller exactly as the battery manual said. The engine alternator is 70 amps, internally regulated. I don't actually have the details on the internal regulator regime. The batteries have had very little use since installation, and very little load demand put on them. I have noted that the cells are slowly bubbling with the engine running (i.e. normal charging), although the solar controller indicates they are fully charged, or close enough. Start battery is AGM, and is on a separate solar float charger.
We are on the verge of diving in and sussing everything, and our initial thought is an issue with how we've set up the new engine alternator, but given its only one battery boiling cells dry, wanted to ask the collective wisdom if this sounds like a battery fault and not a charging issue?