Date:         Tue, 20 Apr 2010 19:12:25 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: charging aux battery: too much of a good thing?
Comments: To: mark drillock <mdrillock@COX.NET>
In-Reply-To:  <4BCE26A7.8010605@cox.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 06:11 PM 4/20/2010, mark drillock wrote:
>Today I was able to fire up my 3 battery system for the first time. A
>dedicated 125 amp hour deep cycle was added for the Vitrifrigo fridge
<snip>
>run the engine to get another night of camping. I was surprised to see
>the meter reading over 60 amps going into the battery when I first

Mark, that's a bit high -- the rule of thumb is 1/4 the amp-hour
capacity for flooded cells, 1/3 for gel cells.  However since it's
only for a few minutes I doubt you'll come to much harm.

If you're getting 14.5 volts at the batteries, that's probably good
for charging itself, but will likely put the batteries in the gassing
range which will boil the water out of flooded batteries fairly
quickly and may harm gel batteries -- I forget.  Normal float voltage
at room temperature should be around 13.6, but the batteries won't
charge either fast or fully at that voltage.  I might suggest going
to a 14.2v regulator, but that will slow down the charge rate
noticeably.  You can regularly check and add water to the batteries;
but the real solution is a three-stage "smart regulator" which isn't
free.  You can manually simulate one for very little money; pmail me
about that if you want.

YOurs,
David