Date: Tue, 26 Nov 1996 14:55:25 -0800
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: Charlie Moore <charliem@isomedia.com>
Subject: RE: Aux Battery
Re:Problem #1. I have been wondering the same thing as I have been =
mentally putting together my aux battery setup.
Re:Problem #2: It is a known problem with isolators to have a .6-1V drop =
across the terminals due most likely to internal diodes. Diodes are =
regularly defined to have a .7V drop. So it depends on manufacturing =
differences to make up the range .6-1V.
An alternative to this is to use what is called a battery combiner. =
These do not have a voltage drop and therefore do a better job =
recharging your battery. The idea is to run your charging circuit to =
one battery. From this battery run a line to the combiner which then =
goes to the second battery. The combiner is only closed when it senses =
a charging level voltage, say 13.8V and opens when the voltage lowers =
to, say 12.1V. Therefore the batteries are combined when charging and =
open when the charge circuit is removed.
This is the modern day equivalent to the relay originally used on =
Vanagons. Apparantely there are some problems that can occur with =
relays on large amperage circuits.
Not sure I understand about blowing up batteries when they are both =
being charged from a single source. This is commonly done and in fact =
in the original Westfalia design the batteries are combined through a =
relay when the alternator is putting out a charge.
The boating world has been dealing with this for a long time and one =
boating supplier, West Marine, has an interesting talk about this. Try:
http://www.iwol.com/iww/customers/westmarine/advisor/electrical/home.html=
You will see in the diagrams something us Westy folks don't usually =
have, and that is a battery switch. You commonly switch your batteries =
off from all loads when leaving the boat. You also can easily combine =
both battery banks with these switches since they have 4 positions; =
Battery 1, Battery 2, BOTH or OFF.
- Charlie.
'87 Westfalia
----------
>From: Wiesner Craig[SMTP:Wiesner_Craig@mm.ssd.lmsc.lockheed.com]
Sent: Tuesday, November 26, 1996 11:35 AM
To: Multiple recipients of list
Subject: Aux Battery
I have been having one hell of a time with my charging system. I hooked =
up a
powerful stereo to the Aux Battery under the drivers seat, as well as =
fog
lights and a back-up light.
Problem #1. I can easily take out the main battery by sliding the =
passenger
seat back and turning it around to face the front. How do I take out =
the Aux
battery? When I turn the driver seat to the side there is still not =
enough
room. The steering wheel prevents turning it towaerd the rear. It =
looks like
I need to remove the seat to remove the battery.
Problem #2. When I drive in alot of stop-n-go traffic the Aux battery =
was
running down to nothing. I checked the battery. It is fine. I put a
voltmeter on the alternator at idle and it reads 13.8v. I put it on the =
posts
on the isolator and they read 12.9v! I am losing a volt in the friggin
isolator! I tried different isolators, same result. I then by passed =
the
isolator and wired the charge wires to both batteries directly to the
alternator. This was working fine. I figured if I stop to camp for a =
while I
would remove the negative post from my main to prevent drainage. Then =
someone
tells me that I could blow up one of the batteries with this set-up due =
to
different charging needs and possible over charge of one battery. So =
now I
have the main battery on the Aux post on the isolator ( supposed to be =
switch
on and off with the engine, 4-post isolator) and both the Aux Battery =
and the
alternator hooked together on the alternator post on the isolater. Now =
my Aux
battery is fine, but my main is slightly under charging in stop and go!
Any suggestions or ideas? I have read all of the posts on Aux batteries =
and
none has mentioned an under charging problem. Will the batteries blow =
if I
leave them connected together?
Thanks,
- Craig
'86 Syncro Westy
