Date:         Thu, 13 Dec 2001 11:17:54 -0500
Reply-To:     "Warner, Jeff (DSIO-MS)" <Jeff.Warner@DSIO.DLA.MIL>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "Warner, Jeff (DSIO-MS)" <Jeff.Warner@DSIO.DLA.MIL>
Subject:      Battery Isolators vs. Relays

> Volks,
>
> One of the things I love about this list is that if you hang around long
> enough the subject you're ready to discuss will invariably come up again.
> To my knowledge, this latest round of discussions regarding isolators and
> relays hasn't yet touched on what I thought was the most important reason
> for using an isolator.  I now see that there are certain disadvantages to
> the isolator but what about the advantages?  I thought the reason for
> going through the significant efforts to install an isolator was to avoid
> a substantial drain placed on the starting battery by a drawn-down aux
> battery when the van is driven after excessive aux battery use.  By using
> the isolator, you keep the batteries separated so that the aux battery
> doesn't pull on the starting battery in a natural attempt to equalize.  Am
> I right here or what?  Or is this problem too insignificant to worry
> about?  Apparently, some who've installed an isolator thought it was
> worthwhile.
>
> I've got an '86 Westy Weekender with the factory aux battery setup.  It
> seems that the DPO didn't even realize the aux battery was there.  They
> complained about having to frequently replace the starting battery and
> even replaced the alternator in an attempt to stop loosing batteries.
> When I got the Westy home and started my usual poking and prodding, I
> discovered an original VW battery in the aux compartment that was dead as
> a stone!  This was their problem!  Every time they'd install a new
> battery, the dead aux battery would start killing it.  I called them to
> see if they knew anything about the aux battery and they were stupefied to
> find out about its existence.  Just an interesting story about a DPO and
> fairly irrelevant to this discussion.
>
> So now I'm considering installing a new aux battery and whether to go with
> the factory relay setup or install an isolator.  I intend to install a
> fuse block and run several accessories off the aux battery including
> subwoofer amp, inverter, lights, etc.  I really don't want a drained aux
> battery constantly pulling at my starting battery whenever the van is
> running but if it's really not that big of a deal I'd just as soon keep
> things simple with the relay.  Thoughts?  This subject also speaks to the
> issue of dissimilar batteries for starting and aux.  Many people seem to
> opt for the Optima batteries or other similar batteries for their aux, yet
> this would seem to me to exacerbate the draining problem with a relay and
> maybe should only be done with an isolator?  I would think that if you're
> using a relay you would want to ensure that the batteries are matched.
>
> My .02 but looking for input.
>
> Jeff Warner
> Galloway, OH
> '86 Wolfsburg Westfalia Weekender "Barry"
> '87 GL Weekender "Van"
>
> PS.  Ron, Do you know if there are any advantages to your Hella kit vs.
> the factory installation?
>
>
> Date:    Wed, 12 Dec 2001 07:15:05 -0500
> From:    The Bus Depot <vanagon@BUSDEPOT.COM>
> Subject: Re: Battery isolator
>
> Just a reminder for those interested in adding a second battery, that I
> sell
> a genuine Hella dual-battery relay kit designed specifically for this
> purpose. The kit includes a fused relay, wiring, and instructions. When
> the
> van is running, the two batteries are wired in parallel and the alternator
> "trickle-charges" the camping battery; when the van is shut off the two
> batteries are separated so you cannot kill your starting battery even if
> you
> completely drain your camping battery. The use of a relay for this
> purpose,
> as opposed to an isolator, eliminates the intrinsic voltage drop caused by
> the diodes in an isolator. Also, in my experience it is more reliable than
> an isolator, and less likely to leave you stuck with a dead starting
> battery
> in the event of failure (which has happened to me several times with
> isolators in VW vans)  The third advantage is cost - just $18.95 for the
> kit.  Part # 1738.
>
> - Ron Salmon
>   The Bus Depot, Inc.
>   (215) 234-VWVW
>   www.busdepot.com
>
>
>