Date: Sun, 22 Aug 2004 23:30:51 -0700
Reply-To: David Marshall <vanagon@VOLKSWAGEN.ORG>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Marshall <vanagon@VOLKSWAGEN.ORG>
Subject: Re: [Syncro] dual battery isolator
In-Reply-To: <JBEOJOBKGBDBEAIBOCBEMECFDJAA.syncrowestytd@mindspring.com>
Content-Type: text/plain; charset="iso-8859-1"
I can't see an issue with a 70A relay load wise as your alternator is 90A
and only on a good day. I use a generic Bosch 40A relay for my 2nd battery
in my TriStar and I have never had an issue and I have a 120A alternator.
Charging battery from a dead flat doesn't make the relay nor the 2x12ga wire
running to the battery hot or even warm to the touch. I think the relay is
the simplest and probably the most effective of designs. The diode
isolators are not good in my opinion as they introduce a 0.7V loss in the
system over both batteries. The computerized isolators that give the
starting battery and deep cycle the voltage they want to see is the best
bet, but expensive and really I think the deep cycle will charge fine on the
relay with an alternator designed to charge a starting battery. 1000s of
fishermen driving home charging their deep cycles on their F150 can't be
that wrong.
David Marshall
Fast Forward Automotive Inc.
4356 Quesnel-Hixon Road
Quesnel BC Canada V2J 6Z3
http://www.fastforward.ca mailto:sales@fastforward.ca
Phone: (250) 992 7775 FAX: (250) 992 1160
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-----Original Message-----
From: Westyman [mailto:syncrowestytd@mindspring.com]
Sent: August 22, 2004 10:15 PM
To: Vanagon list; VWVANFULLTIMERS; Syncro list
Subject: [Syncro] dual battery isolator
Hope this doesn't start a whole new argument on the subject, but I seek
input from those who may have done this:
I'm installing a group 29 deep cycle battery as my main camping battery in
my Westy [no, it won't fit under the front seats!] to power my new 12-volt
Norcold DC-0040 fridge. Yes, I finally had enough of dealing with the
unreliability of the old Dometic! What I'm concerned about is the different
charge rate required between the deep cycle and the main battery. The main
will likely never be drained below 75-percent, but the deep cycle may become
very drained, and often. I currently have a 70-amp relay connected as in the
stock Westfalia method for dual batteries. Will that work 'OK', or do I need
to use some other method or isolator? It seems to me that the alternator
would not charge two batteries of different types and levels of drainage
efficiently. Comments? Thanks.
Karl Mullendore
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