Re: (ET) RE: float charger question...

["David Roden (Akron OH USA)" <roden ald net>]

On 10 Oct 2002 at 11:45, Chapin, Tim wrote:

> Getting the boats put away for the season and want to keep the 2 12 volt
> batteries in good shape.  Can I take a cheap float charger rated for 5 
> to 125
> amp hour batteries and maintain both batteries at one time? 
> 

Yes, you can parallel them (+ to +, - to -) IF both are in good condition 
and of equal age.  Before doing so, measure the resting voltage of both; 
they should be within a few hundredths of a volt.  If they differ by 
tenths 
of volts, it's safer not to parallel them.  (Resting voltage means they 
have 
been sitting uncharged and unused for at least several hours, preferably 
24 
or more.)

Note that most cheap chargers aren't float chargers, but trickle chargers. 
 
These will overcharge the batteries.  A true float charger is tightly 
voltage-regulated and thus isn't cheap.  

One source of good float chargers is used ~high quality~ UPS systems.  
(The 
$150 ones sold for desktop computers are not what I mean by high quality.)

You don't really need a float charger, though.  If your batteries are gel 
or 
AGM type (nonspillable), they don't need any charging at all.  Store them 
somewhere cool and dry for up to 3 months.  If your batteries are flooded 
type, connect a good automatic charger to them about once a month and let 
it 
run for a few hours, or until it shuts off.


David Roden - Akron, Ohio, USA
1991 Solectria Force 144vac
1991 Ford Escort Green/EV 128vdc
1970 GE Elec-trak E15 36vdc
1974 Avco New Idea 36vdc
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