Date: Sun, 9 Aug 1998 13:50:50 -0400
Reply-To: Michael Sullivan <sullivan@OPENMARKET.COM>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: Michael Sullivan <sullivan@OPENMARKET.COM>
Subject: Re: Aux. battery questions
Content-Type: text/enriched; charset="us-ascii"
At 05:43 PM 8/4/98 EDT, S Sittservl wrote:
>(1) By what route have people run the wire from the starting
>battery to the auxiliary battery? Under the carpet? Under
>the floor? Do I drill a new hole in the starting battery
>compartment?
The classic route is to drill two holes (or better yet use a metal punch) -- one in the main battery compartment, and the other in the aux battery compartment. Edges should be primed and painted. You MUST use robust rubber grommets -- go to a junkyard. I chose to only drill one hole in the aux battery compartment as per above. I routed the cable from the main battery out through the vent channel instead of drilling another hole in the main battery compartment. Also, be sure to fuse the main conection with a 60amp or higher fuse.
>(2) How much amperage will flow across that wire? I need the
>amperage to figure out what size wire, relay, and fuse to use.
>If I have a 90 amp alternator, do I need to be prepared for 90
>amps on that wire? If I want to be able to jump start my
>(dead) starting battery from my auxiliary battery across that
>same wire (I could put in a by-pass switch across the relay to do
>this), then how many amps are there during a jump?
Well, theoretically, IF the aux battery were completely drained, THEN the possiblility exists that the full 90amps would attempt to flow across to the drained battery after the engine started. This has been documented by others who opted to use the "stock" relay -- the fuse blows, naturally, to protect the circuit. With such a tivial setup, you then need to jump the batteries together to get the aux battery back to charge -- yuch!!
THUS, it makes sense to use the biggest wire practical. I chose to use a 4 gauge direct connection between the main battery and a 100amp "battery switch" relay available at RV stores and Solar Panel distributors (check the web). This battery switch only costs about $18 and has 5/16" connections -- perfect for 4 gauge wire. With this setup, there is no need to use a manual switch at all.
>I should mention that I'm currently leaning toward putting in
>a new relay, rather than using the fridge relay. But:
>
>(3) If I were to use the fridge relay, is the existing "+" wire
>from the starting battery to that relay really heavy enough to
>handle the current between the starting battery and the
>auxiliary battery? I realize many people have used it, but
>it looks kind of thin to me. If I use it, should I add a fuse
>to it? Similarly, is the relay itself really heavy enough?
>
>Steven Sittser
It is simply too small a gauge. Go with your gut instincts -- use 4 gauge.
Cheers,
<bold>Michael J. Sullivan
</bold><italic>Director of Catalog Design
Open Market, Inc.
</italic>
'87 GL Syncro Westfalia
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