[C320-list] Mixing flooded and sealed batteries

[Bruce Heyman]

Hi Jerry,

Unless the batteries are wired totally separately, in separate battery banks
and charged separately from both the alternator and the AC charger I would
not replace one at a time.  

Even if you stay with the same battery chemistry and if they are in the same
bank (two 6v in series or two 12 volts in parallel) you should not even mix
batteries of different ages.  Ideally you will/should get two batteries from
the same manufacturing batch.  Otherwise they will always be less than
optimal.  The new one will give up a portion of its energy charging the
older/weaker one.  

Batteries of different chemistries have different absorption characteristics
and different internal resistances that guarantee charging will not be
efficient and may prevent the new battery from ever achieving float.

Afraid you have to bite the bullet and replace them both.

Best,
Bruce

Bruce Heyman
bruceheyman at cox.net
(949) 289-8400
Somerset #671 Dana Point (temporarlily(?) Cabrillo Landing, San Pedro), CA

-----Original Message-----
From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf
Of Jerry Clayton
Sent: Saturday, June 28, 2014 9:48 AM
To: C320-List
Subject: [C320-list] Mixing flooded and sealed batteries

I currently have 2 flooded 4D batteries.  One battery will need to be
replaced soon and I am considering switching to a sealed HD battery.
My question is can I mix a battery with slightly different specs or will it
cause any problems with the charger. I would replace the other battery when
needed with a maintenance free battery so they would then both match down
the road.
I have the standard Charles charger that came in 2004 models.
Here are the specs for the existing battery (1) and the new sealed battery
(2).
            CCA at OF               RCmins at 50f
1)           1000                             1250
2)             900                             1125

I did notice that battery 1 weighs 120lbs vs battery 2 at 102lbs so maybe #1
is more of a truly HD unit.  I have been using flooded batteries since the
boat was new and never had to add water very often, but just thought about
adding a sealed unit this time.
I don't think it would create any problems.
Any thoughts?

Jerry Clayton
#988 (2004)