T&T: Hot Battery

[capteric36@sbcglobal.net]

 Ok then.
 Take a digital voltmeter and read the voltage on
the battery posts when the charger is in the
'float' mode.
 Measure the temperature of the batteries.
 The correct float voltage for an AGM battery
changes with temperature.  Ask the manufacturer
what the proper float voltage for your batteries,
at the temperature your batteries have and adjust
the charger to provide that voltage!
You are getting what is called 'Thermal Runaway'
which is the result of the temperature coefficient
of the batteries.
 When the battery temperature goes up the proper
float voltage goes DOWN. Thus the only remedy to
your situation is to install a temperature sensor
on the battery and connect it to a temperature
compensated charger.
 I don't know whether your charger has this
capability or not, but you need it.
 It would also be a good idea to use a thick
aluminum plate that extends under all of the
batteries that are connected in parallel so they
all stay very close to the same temperature.

 And, by the way, Concord (the manufacturer of the
AGM batteries in MY boat) DOES INDEED say that the
parallel batteries all need to be the same age,
even from the same date code (or manufacturing
run, if you prefer) in order to prevent the EXACT
symptoms you are describing.

 I know it is not a popular concept, but you might
want to call the manufacturer and follow the
instructions they give you regarding building a
parallel battery bank.

 OK. I'm done.

Eric Thompson
S/V Procrastinator
South San Francisco
capteric36@sbcglobal.net