[C38] House Batteries

[Les]

Hi, Phil,
	All wetcell batteries tend to develope some sulfation over time.  The
battery then has higher internal resistance and will not charge as
deeply thus shows low capacity.  Many marine battery chargers offer an
Equalizing charge capability.  To do this, they run the voltage up a bit
(about 15.6 to 16v typically) and apply about 10% of battery capacity as
the charge current.  This causes the plates to heat a bit, expanding
them, and drops the calcification into the bottom of the battery.  Good
deep cycle batteries, like your Trojans have a deep tray in the bottom
to "capture" this calcification and keep it from shorting the battery
plates out.  If you keep a charger on the batteries all the time, this
accelerates the calcification slightly, but typically once a quarter,
equalizing them will keep their life up.  Also that deep discharge with
the 100A shunt will also heat the plates and drop some of the
calcification off, but is not as effective as the two hour equalizing
charge.  Some chargers can even be set to do this automatically, but I
wouldn't recommend it.  The leads and batteries do get hot, and fire
though unlikely, could result.  If the charger has a temp sensor that
helps mitigate the risk.

	If your charger doesn't provide an equalizing charge, perhaps you can
take the batteries to a good battery shop and have them put them on an
equalizing charge while you have a long lunch?  It might help, and
couldn't hurt.  But check your charger's manual.  Many marine chargers
are capable of this and only need to have it triggered somehow.

Regards,
Les H
On Wed, 2007-07-18 at 21:44 +0000, eyriepg at comcast.net wrote:
> Two and a half years ago I installed a pair of  Trojan 6V golf cart
> batteries in my boat.  The have never been abused but it seems like
> they discharge significantly quicker than they used to.  I doubt that
> they have been dischared below 12.0 volts more than 5 times.   I
> hauled them out of the boat and had them checked at my battery store.
> The checker put a 100 amp load on them for a few seconds and
> pronounced them good.  Is this a good test for the capacity of a deep
> cycle battery?  How do you know when it is time to replace your house
> batteries?  I am thinking that I should install an amp-hr meter.
>  
> Phil Gay
> C38 094 Que Linda
> Everett, WA
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