batteries bubbling and warm/hot

[CharlieJ]

A charger should bring a healthy FLA battery bank to the "gassing voltage" before cutting back to float voltage. "Gassing voltage" is that point where very small gas bubbles just start to form and rise through the electrolyte providing some mixing and agitation and is generally >14.2VDC at 77F. Gassing voltage is temperature dependent; low temperature requires higher voltage and vice versa and is the reason that I recommend temperature compensated charging sources for an optimum system.

BTW, Series 31 batteries are not "deep cycle", no matter what the label says. They are classed as starting, lights and ignition (SLI) batteries and utilize thin plates to deliver a lot of power in a short period of time.

In general, you cannot "cook" your batteries unless the charging voltage gets excessive. With your new installation, monitor the batteries at the battery posts with a DMM through a charge cycle.

[foggysail]

Do not overlook the charger. And I wonder why nobody suggested using an hydrometer to test your batteries. If your charger's internal regulator has failed, who knows what problems will result. Finally, those old ferroresonant transformer style chargers have large voltage spikes on the waveforms that will boil out a battery's electrolyte.

You now have new batteries! You will know soon if the charger is a problem source.

[svHyLyte]

Originally Posted by Deep6

Thanks everyone for the replies, I've now replaced both with 2 new deep cycle wet cell G31s. My charger has now adopted a 6 amp charging output for the last 24 hours which seems like it should have dropped by now. Thus I have turned off the charger now fearing I may be cooking these batteries as well... They're cool to the touch and are showing a voltage of about 12.9 which ai believe is near full charge. Should my charger have dropped to a lesser amp output or am I overly paranoid now? Lastly, if the charger should be cooked as well has anyone any recommendations for a charger/inverter as I might as well service both needs. Any guidelines for sizing an inverter as well?
Thanks everyone.

What else is powered on? If you are a live-aboard, you may be pulling amps for lights, refrigeration, propane monitor and what have you that the charger is fulfilling as well as keeping your batteries in float mode. Refrigeration alone can easily pull 4-5 amps.