Date:         Mon, 6 Feb 1995 23:52:51 -0800
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         rickgo@halcyon.halcyon.com (Rick Gordon)
Subject:      Westy auxiliary battery setup

>
>I have an '81 westy and was thinking about a auxillary battery for
>camping. I have a auxillary heater, so this would come in handy as well
>as using the radio and lights etc. Is there anyone who has done this
>procedure who has an opinion? I went to JC Whitney and there set-ups do
>not accommodate a stock Bosch alternator. ---Steevo---

I've got a '80 ASI conversion, which had mods for an aux battery.
These mods consisted of one of those isolators you can get at many places,
a cable disappearing into the body only to reappear under the drivers seat,
and appropriate ground and feed to the power-pack.

These mods were ripped out around 1988 by some mechanic who left notes
saying that they were causing a slow drain on the alternator, and that he
had replaced them with an X-switch just as in the later model Westies.
(You can find a circuit diagram of this in the Bentley book. The X switch
is just a current activated electromagnetic switch. You can find these at
auto parts stores - if nothing else look under parts for VW Rabbits.)

When I bought the van there was a dead battery under the seat and no
X-switch to be found. I actually located the guy who did the original work
and while he didn't remember that van he told me where he would have put
it. it wasn't there or anywhere.

So I bought an X-switch, taped (temporarily) it into the engine
compartment, ran the wire from the alt that feeds the dash alt light to it
(to activate it), and it's all functioning correctly: when the alt is
running, the current feed to the switch connects the two batteries. When
the current is off, they're isolated.

There are two problems however:
1) voltage across the aux battery is insufficient to charge it. I think
they recommend 13-14 Volts, and I'm not getting that. Voltage across the
primary battery is fine. Possible causes: cable length between alternator
and aux battery, voltage drop across the X-switch, insufficient alt output.
Or simply could be a combination of the first two compounding the last one.
Anyone know what the voltage output of a std alternator is offhand? Bentley
mentioned a couple of choices and I'm not sure which I have yet.  Cable
from engine compartment to driver's seat is long, but it looks like a 10
AWG cable.
(I haven't been out to work on this in a couple of months so I may be wrong
there - close though.) Maybe a different voltage regulator? But is there
danger to the FI control box from such a change?

2) the battery isn't deep-cycle, meaning, I'm told, it's only got about 30
full deep discharge cycles to it. It was the only battery I could find that
would fit under the seat, and I'm new to this camper business. Solution
here, unless I can find a deep cycle that will fit under the seat, is to
get a real deep-cycle and put it in the storage compartment under the
middle seat. But this means a lot of rewiring (including ones that aren't
visible from underneath) connecting the charging system to the battery as
well as connecting the batteries.
If anyone knows of std VW height deep cycle batteries DO let me know!

Oh yeah, since I did this, I noticed that the EGR and ALT lights come on
until I rev the motor sometimes. Maybe they did before and I just didn't
notice it. Others have said they have similar behaviour. also the lights
seem to glow just barely when the engine is revved. only visible at night.
and they stop at idle!

So right now I only use the aux battery sparingly, say keeping the fridge
going for a few hours while driving, and maybe some interior lights when
needed.
Then I charge it up on the charger at home. I've got a battery gauge on the
power converter, so I can tell when it's about half-charged.

I suppose at this point I should just draw the whole system out, figure out
drops across various components, and see what's wrong. I just haven't had a
lot of time to mess with it lately. There's always a paid mechanic I
suppose, but this is an electrical problem and I *should* be able to figure
it out.
(when I went to school computer science meant a couple of EE courses too!)

let me know what you figure out, maybe it'll help me!

-rick

Rick Gordon
Bainbridge Island, WA
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