John,
I don't know about an 81 van, but here is what I found out working on my 90
Syncro Westy.
Bill
-----Original Message-----
From: Davidson <wdavidson@THEGRID.NET>
To: vanagon@GERRY.VANAGON.COM <vanagon@GERRY.VANAGON.COM>
Date: Wednesday, March 10, 1999 5:31 PM
Subject: Auxiliary Battery Madness (looong)

>Volks,
>Just thought I would share my research on auxiliary battery, switches,
amps,
>wire, fuses, etc.: Between this post and Harald's two posts (mentioned
>below), I think a lot of things may become clearer about setting up and
>auxiliary battery in a Vanagon. Enjoy the madness!
>
>Thoughts on Connecting an Auxiliary Battery in the Vanagon:
>March 1999
>
>Disclaimer:
>I am not an electrician or a mechanic. Nothing that follows is meant to be
a
>recommendation. I am only communicating the results that I have found on my
>particular Vanagon and the conclusion that I have come to regarding those
>results. My results may be flawed, my conclusions may be wrong, and/or your
>vehicle may be different than mine. Wiring is nothing to play with; it can
>cause fires and serious damage to your vehicle and its occupants. I
>recommend that you employ the knowledge and skill of a competent mechanic
>when making alterations to your vehicle.
>
>Background:
>About a year ago I decided I wanted to install an auxiliary battery in my
90
>Westy Syncro. First, I had a Sure Power isolator installed by a mechanic.
It
>never worked properly. Then I discovered a write up on installing an
>auxiliary battery at the vanagon.com web site. The basics of the article,
as
>my way over 40 memory allows, were that most of the later model vanagons
>came equipped with a relay switch in the box under the driver's seat and
>that all you had to do was to install the auxiliary battery between that
>relay and the two wires that run to the fridge and other camper stuff. I
>printed out the article, gave it to another mechanic, and he installed an
>auxiliary battery per the directions in the article. I used this set up
>during a six week camping trip to the Southwest, and it seemed to work
fine.
>Then in the past month or so this topic came up again on 'the list'. I
>promoted the solution that had worked for me because it worked. But Harald
>pointed out that the stock relay and wiring were inadequate for a safe
>installation. There was a fair amount of constructive debate, and I
realized
>that there was much that I didn't know on this subject.  After delving into
>the Bentley wiring diagrams, inspecting the stock wiring, reading a crash
>course in Automotive Electrical Wiring by Haynes, consulting wire sizing
>charts, measuring actual current draws, pondering time vs. amps fuse
charts,
>and considering many relevant posts to the list I have come to some
>conclusions. I share some of that research and those conclusions below.
>(This is more of a research article than a 'how to' article. For an
>excellent 'how to' article on installing an auxiliary battery see Harald's
>posts: Part 1 was under the heading: Re: Flash Alert! Dual Battery Relay
>date 1/29/99 and Part 2 was under the heading:
>Dual Battery Relay-Part 2 [long] date 1/31/99)
>
>Switch Choices (pros and cons):
>
>Manual Switch:
>A manual switch is simple, and it is inexpensive. It simply connects or
>disconnects the positive terminals of the starter and auxiliary batteries.
>There are fewer things to go wrong with a manual switch. To charge the
>auxiliary battery, you simply use it to connect the starter battery and the
>auxiliary battery (close the circuit) after the engine is started and to
>disconnect them (open the circuit) before or just after the engine is shut
>off. The main problem with a manual switch is remembering. If you do not
>close the circuit after the engine is started, then you will not be
charging
>the auxiliary battery. If you do not remember to open the circuit after the
>engine is stopped, your appliances can drain the starter battery to the
>point that it will not start the engine.
>
>Relay:
>A relay is generally used as a remote switch that can be set up to work
>automatically. You don't have to remember to connect and disconnect the
>starter and auxiliary batteries. That is done by a pair of actuator wires
>that are 'live' only when the alternator operating. When these actuator
>wires are live they force the contacts inside the relay that carry the
>current between the two batteries to physically contact each other. This is
>probably the most common non-manual switching device in the automotive
>industry. Because of this I am inclined to believe it may be the most
>reliable and most readily available. And they tend to be the cheapest.
>The disadvantage of using a relay is that if it fails it could fail with
the
>contacts touching. If this happens you may not know about it, and your
>appliances will drain both batteries leaving you unable to start the
engine.
>
>Solenoid:
>A solenoid is very similar to a relay. Generally they are used as a remote
>switch between the ignition and the starter, and they are designed to
handle
>much larger currents than relays.
>It is my understanding that Solenoids have pretty much the same
disadvantage
>as a relay. In addition, since the contacts are larger in order to handle
>larger currents (often over 160 amps compared to the typical automotive
>relay rated at 30 or 40 amps), the actuator current must be larger in order
>to move the contacts into place. There has been some concern expressed on
>the list that the actuator circuit was not designed for and could be
damaged
>by this larger actuator current.
>
>Isolator:
>These are the square or rectangular boxes with colorful fins. It is my
vague
>understanding that isolators do not connect the two batteries. They are a
>solid state device that directs charging power from the alternator to the
>each of the batteries independently depending on whether each battery needs
>a charge or not.
>It is my opinion that the main disadvantage of the isolator for the Vanagon
>owner is that there have been many anecdotal reports that it is difficult
to
>get the isolator to work correctly with the Vanagon. Even the tech support
>person at Sure Power said this to me. (I think this is because the Vanagon
>alternators put out less voltage than the typical American vehicle and
there
>is also a voltage drop across the isolator, thus not leaving enough voltage
>to activate the solid state switch. I think.) That being as it may, Harald
>has reported that he prefers the isolator and it seems to work fine in his
>vanagon.
>
>Another disadvantage is that this device is larger, making it harder to
find
>a place for it. And it should not be installed in a hot environment (the
>fins are meant to dissipate internal heat). Also, according to Bob
>Livingston (RV Repair & Maintenance Manual, p. 1.20), other problems that
>can be caused by the isolator include: 1) a shorted diode can cause the
>battery(s) to overcharge or boil (I think this is because the isolator
>essentially replaces the stock voltage regulator.) 2) an open diode can
>cause one battery not to charge or both batteries to go dead, and 3) a
>defective diode can cause low battery voltage.
>
>Battery Combiner:
>This device is offered at West Marine (a boating supply store), and the
>device has the West Marine name on it. It measures about 4 x 4 x 3 inches,
>and I believe this too is a solid state device. As I understand it from
>reading the box, the Battery Combiner combines the starter and auxiliary
>batteries while they are charging (above 13.1 volts) and isolates the two
>batteries when the are discharging (below 12.8 volts). Unlike the isolator,
>West Marine claims that there is no voltage drop across the Battery
>Combiner. There are two models, one rated at 50 amps and one rated at 150
>amps.
>The disadvantage of the Battery Combiner is that it is relatively new and
>unknown. I haven't read or heard any independent review or anecdotal
>evidence regarding this product. It also concerns me that it takes 13.1
>volts to activate the device. My experience in measuring the voltage output
>of the alternator at my battery is that it goes down very close to the 13.1
>volts and is known to vary considerably.
>
>Amps Measured:
>
>Relays/Solenoid actuator amps:
>The purpose of this test was to determine amperage draw of the actuator
>circuits for various relay & solenoid options. The idea was to avoid
>choosing a relay or solenoid with significantly higher amperage draw than
>the stock relay and the associated higher risk of damaging the actuator
>circuit.
>
>30 amp Bosch relay:   180 mA
>75 amp Bosch relay:   245 mA ($17 from Alternative  Energy)
>160 amp Tekonsha solenoid:  750 mA (Sold at Camping World)
>(All tested with digital ammeter in line with one of the actuator wires in
>my 90 Westy Syncro.)
>
>I do not know for certain the amp rating of the stock 'battery cut-out
>relays' (Weekenders only) or the 'fridge cut-out relays' (Full Camper). But
>I did see a Wolfsberg Weekender in a junk yard that had obviously been set
>up with an auxiliary battery. The 'battery cut-out relay' looked original.
>It was a 30 amp Bosch relay.
>
> Auxiliary Battery Amperage draw:
>The purpose of this test was to determine maximum amperage draw of the
>auxiliary battery circuit (including appliances) in order to choose the
>battery switch hardware and to size the wire running between the batteries.
>
> Test 1: (Aux Battery run down to 8.3 volts under 2 amp load; 9.7v no load;
>Starter Battery 12.6v)
>
>Aux Batt only:     surge to 25 A;    steady at 20 A
>Aux Batt + 12v fridge + 2 - 1 amp lights:  surge to 45/50 A;  steady at 35
A
>
>Test 2: (Aux Battery discharged to 2.5 volts under  2 amp load; 4.3 V no
>load; Starter Battery 12.6 v)
>
>Aux Batt + 12v fridge + 2 - 1 amp lights:  surge to or above 75A;  steady
at
>30 to 45 A
>                 (radiator fan on and off)
>
>(All tests were done with the engine running and the starter battery and
the
>auxiliary battery connected in parallel with #4 wire. The positive
>connection was manually switched to start the test. All the amp
measurements
>were with an inexpensive analog inductive ammeter that measured a maximum
of
>75 amps. My guess is that they can be considered accurate to + or - 10% or
>so. The surge amps lasted only a fraction of a second. Ambient temperature
>was about 60 F.)
>
>Starter Amperage off Main Battery:
>With the intention of using the auxiliary battery as a back-up starter
>battery (without having to use jumper cables), the purpose of this test was
>to determine the amperage draw of the starter in order to size the wire
>between the batteries and the fuses at both positive terminals.
>
>surge to 300 A; rebound to 125 A
>(measured at + post) (total about 1/2 second)
>(average maybe 150  to 175 amps)
>
>Well, the measurements do not have digital accuracy, but I think they help
>zero in on the appropriate sizing of wire, fuses, relays, etc.
>
>My Personal Data Conclusions (Opinions):
>I think Test 1 shows how marginal using the stock wiring and relay can be.
>Typically I would run my Auxiliary Battery (Optima) down to 10.5 volts with
>my lap top computer. 10.5 volts is about the lower limit for many
>appliances. Then when I left camp I would switch the fridge over to 12 volt
>and start the engine. So I must have been drawing between 20 and 30 amps
>(the fridge is 7.5 amps) over about a # 13 wire (2.5 mm sq in Bentley) and
>through a 30 amp relay. (My stock "fridge cut out relay"[Bentley term for
>the Westfalia relay] was replaced with a 30 amp Bosch relay and I don't
know
>what the amp rating of the original "fridge cut out relay" was. If it was
>less than 30 amps then Test 1 would show it to be less than marginal.)
>
>And I think Test 2 shows what would happen if I left some interior lights
>and/or the fridge on 12 volts by accident over night. Surging to 75 amps
and
>a steady draw of 40 amps would make the stock 2.5 mm sq wiring and relay
(30
>amp or less?) of the Westfalia woefully inadequate. Even upgrading to a  40
>amp relay with the Weekender #10 wiring (6.0 mm sq in Bentley) would be
>marginal. (The Weekender relay is called a "auxiliary battery cut out
relay"
>in the Bentley. It is apparently a 30 amp relay as that is what I observed
>in a Weekender wreck at a junk yard.)
>
>I decided to upgrade my auxiliary battery charging circuit so that it would
>have a margin of safety even if I made the mistake of leaving appliances on
>overnight to find a deeply discharged auxiliary battery in the morning.
From
>the data above and wire sizing charts I decided that I would use a minimum
>of #8 wire and a relay rated over 40 amps. And then I decided that if I
used
>#4 wire I could use my auxiliary battery as a starter battery in the event
>that my starter battery died. This larger wire would also allow my
auxiliary
>battery to charge faster than with # 8 wire.
>
>My Personal Choices:
>
>Switch:
>As outlined above, the various switches all have there advantages and
>disadvantages. I wanted a switch that would fit in the auxiliary battery
>compartment with my Optima battery, and I wanted something simple and
>dependable. I felt that narrowed my choice down to the relay or the
>solenoid. I went for the Bosch 75 amp relay (part # 0 332 002 150) over the
>solenoid because its actuator circuit draws only 245 mA, much closer to the
>180 mA draw of the stock 30 amp relay than the solenoid.
>As you can see from the wiring schematic below, I installed the relay as a
>bypass of the Hella (#87181) 100 amp manual switch (West Marine # 598375).
>(Or, depending on how you look at it, I installed the Hella manual switch
as
>a bypass of the relay and Bussmann Maxi fuse.) I used # 6 wire for the
>fuse/relay 'bypass' because the lengths were short and it is easier to work
>with in the limited space. Even #8 wire would have been adequate for the
>fuse/relay 'bypass' since the #4 wire is only required for using the
>Auxiliary Battery as a starter battery. One of the nice things about this
75
>amp Bosch relay is that it has screw terminals� perfect for #8 or #6 wire.
>(You just don't find spade connectors for these larger size wires.)
>
>Wire:
># 4 starter battery + terminal to Hella manual switch
># 4 Hella manual switch to auxiliary battery + terminal
># 4 auxiliary battery - terminal to metal battery box
># 6 starter battery side of Hella manual switch thru Maxi Fuse holder to 75
>amp Bosch relay
># 6 Bosch relay to auxiliary battery side of Hella manual switch
>(Anchor Marine wire is MUCH more flexible in these larger sizes and nicer
to
>work with in the small spaces of the battery box.)
>
>Fuses:
>I special ordered the Bussmann Maxi Blade Fuse (Max-60) through Kragen and
>installed it between starter battery side of Hella manual switch and Bosch
>relay (Installed in HHX In-Line Fuse holder for Maxi Fuses, #6 lead wires).
>
>Two Blue Sea Systems 150 amp Mega Fuses (bolt-in high current, time lag
>fuse) to protect the #4 wire connecting the two batteries in the event of
>catastrophic grounding (If the #4 wire grounds it will draw current from
>BOTH batteries!). (I intentionally fused this on the low end for using the
>auxiliary battery as a starter battery because it will be seldom used, and
I
>want to have the quickest fuse burn out in the event of grounding.) One is
>bolted to auxiliary battery + terminal and # 4 wire that runs to Hella
>manual switch.
>The other one is bolted to starter battery + terminal lug tightening bolt
>and # 4 wire that runs to Hella manual switch. (Bussmann shows a time lag
>fuse designed for battery cables on its web site. It is about the same size
>and style as the Blue Sea Systems Mega Fuse. I would have chosen this ABI
>fuse, but it will not be in production until around the beginning of the
>year 2000. You will then be able to order it from your FLAPS� just order
and
>ABI 100 or ABI 125� etc for 100 or 125 amp rating. But you really need to
>study the time/amp chart on the web page to make an intelligent decision.
>Same with Blue Sea.)
>
>Battery:
>Optima Deep Cycle (yellow top w side posts). This is the largest deep cycle
>battery that will fit (on its side) in the auxiliary battery box under the
>driver's seat. I don't have to worry about it giving off poison fumes since
>it is sealed. I laid it on its side (top posts pointing forward), and had
to
>cut two notches (one for each top post) in the curved metal plate at the
top
>forward part of the battery box. Also cut two notches in the hinged lid of
>the battery box�. One for each of the side post bolts� just to prevent
>contact of the side post bolts with the metal lid. I taped over these
>notches with black duct tape, and it is hardly noticeable. I made a couple
>of wooden wedges to hold the battery in snuggly. Also lined the battery box
>with thin plastic to prevent any of those many wires from accidentally
>grounding.
>
>Wiring Schematic:
>(In case this doesn't line up in email format, just line up numbers 1 thru
9
>at the left hand margin. Dashed lines and slashes indicate wire pathways,
>periods are used only as spacers to keep things aligned.)
>
>1�.. #4 ---- Metal Battery Box
>2�� \
>3��./
>4��(-)
>5��Optima (+)  ---- #4 ---- Hella Manual Switch ---- #4 ---- + Start
Battery
>6������������..\������./
>7������������.#6�����..#6
>8������������. /������.\
>9��������Bosch relay ----- #6 ----- Maxi Fuse
>
>Basically, you can think of this as a manual switch set-up with a relay by
>pass for automatic operation.
>The large #4 wire and the manual switch allow me to us the auxiliary
battery
>to supply the large amperage needed to jump start the starter battery in
the
>event that it fails. It also allows me to charge the auxiliary battery
>through the manual switch in the event that the relay by pass fails.
>
>Specialty Parts Sources:
>
>Alternative Energy Engineering, orders: 800-777-6609, tech support:
>800-800-0624,
> www.alt-energy.com
>[quality wire, large size wire connectors, 75 amp Bosch relay, 'Battery
>Switch' solenoid]
>
>Camping World, 800-626-5944, www.campingworld.com [Tekonsha 'Battery
Switch'
>Solenoid]
>
>West Marine/E&B Marine Supplies, 800-262-8464, www.westmarine.com
>[quality marine wire, large size wire connectors, Battery Combiner, Hella
>manual battery switch, inexpensive large wire connector crimper (#6 to
4/0)]
>
>Information Sources:
>
>Battery Specifications & tech support (size, amp storage capacity, cranking
>amps,
>charging time, etc.)
>Optima, 303-340-7440, www.optimabatteries.com
>
>Fuse Products & time vs. amps charts:
>Bussman, www.bussman.com
>
>General Automotive Electrical:
>Haynes Automotive Electrical Manual, Haynes Publishing Group 1989.
>[available at most automotive parts stores]
>
>Isolators vs. Solenoids:
>RV Repair & Maintenance Manual, Trailer Life Books, Third Edition, 1998,
>Bob Livingston. [available at Camping World]
>
>Vanagon Wiring Diagrams:
>Volkswagen Vanagon Official Factory Repair Manual 1980 > 1991, Robert
>Bentley, July 15, 1991. [available at VW dealers]
>
>Wire Sizing:
> Alternative Energy Engineering: charts at www.alt-energy.com
> Haynes Automotive Electrical Manual: charts on page 67
>        West Marine 1999 Catalogue: page 402
>