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Re: Battery Chargers ('Maintainers')

To: ewcorco@erenj.com
Subject: Re: Battery Chargers ('Maintainers')
From: Joe Worsley <worsley@ebicom.net>
Date: Tue, 04 Nov 1997 14:07:36 -0800
Cc: triumphs@Autox.Team.Net, tr8@mercury.lcs.mit.edu
Organization: Unorganized
References: <v01540b02b085c7f44449@[159.70.5.217]>
ewcorco@erenj.com wrote:
> 
> I'm considering keeping a couple of batteries from my three season vehicles
> on a battery charger (or maintainer) through the winter.  Several
> questions: (1) is is worth the trouble in terms of preserving the overall
> health of the battery? (2) any units out there that you would, or would not
> recommend? (3) is it possible to keep more than one battery at a time
> hooked up to it?  (4) do you run them continuously, or periodically?
> 
> Thanks in advance for any info.
> 
> Ned Corcoran
> 1971 TR6

You only need enough charge going in to the batteries to compensate for 
the internal leakage of the batteries.

If you paralled two batteries you will have current circulating between 
the two until one discharges enough to match the voltage of the other.  
The only proper way to parallel batteries is to use a isolator diode in 
series with each battery as is done in motorhomes and other similar 
situations where more than one battery is charged from one source. 

Automotive batteries are designed for high current drain and short life 
compared to a battery that is designed for standby power and kept on a 
trickle charge all the time and only used for light long term discharge 
loads. We have standby power batteries on electronic systems that are 
over 20 years old and still perform like new.  They are warentied for 20 
years.

Without the isolator paralleled batteries will charge charge up to the 
value of the charging voltage and one will discharge slightly into the 
weaker (one with lower terminal voltage) one when it is off .  If the 
charger is a automatic (one that shuts off or comes on once in awhile to 
compensate for losses) charger you will have the discharge cycles each 
time it goes off. Some taper off the charge but keep a continous small 
charge on the battery all the time.  The maintenamce current needed is 
probably only around 100 ma.  This would be the better type to use as it 
keeps the constant maintenace charge on all the time and would eliminate 
the discharge cycle.

Small steady output chargers that put out less than a amp or just a 
maintenace charge are available pretty cheap at Wallmart or autoparts 
stores. With a steady low charge you can do without the isolators.

Kinda long soapbox speech huh!  You'd never guess I like to talk.

Joe Worsley
80 TR8
72 TR6
Tupelo, MS USA

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