Harald,
Thanks for going to the trouble to write this auxiliary battery information
up.
After reading it I have a couple of questions:
1.    The $62 VW relay that you mentioned, how many amps is it rated for?
And is it a Bosch? I wonder because my FLAPS has a 40 amp 4 post Bosch relay
for about $8.00.
2.    It is interesting to me that in some of the previous posts discussing
the wire size and relay amp ratings, it was mentioned that a drained
auxiliary battery could draw the total potential output of the alternator. I
believe that would be 90 amps. I had a short talk with a tech guy at Optima
the other day and he confirmed this possibility. If that is the case, I'm
wondering why we are messing around with 40 amp relays and fuse/breakers?
3.    It seems that in some places you mention 'breaker' and in some places
'fuse'. Can you or anyone comment on the relative virtues of the two in this
auxiliary battery application? I did notice that Sure Power uses a 50 amp
circuit breaker (auto reset I believe) in the kit that they sell. I'm not
sure how even a 50 amp breaker would work in the event of a drained
auxiliary battery and a 90 amp current. It is also interesting to me that
they put their 50 amp breaker between the auxiliary battery and the
isolator. I don't understand what they are trying to protect. (Perhaps the
#8 wire?)
Thanks for your answers,
Bill
90 Westy Syncro
-----Original Message-----
From: harald_nancy <harald_nancy@EARTHLINK.NET>
To: vanagon@GERRY.VANAGON.COM <vanagon@GERRY.VANAGON.COM>
Date: Sunday, January 31, 1999 12:33 PM
Subject: Dual Battery Relay - Part 2 (long)

>Hi Volks,
>How to install the battery cut out relay. Second part.
>I already posted a list of: Items you might need for this
>installation. I posted this on Friday, January 29, 1999 at 10:49 am
>under the title "Re: Flash Alert! Dual Battery Relay".
>
>To be on the safe side, you can purchase a relay for 2 batteries
>from the VW dealer. It would be the most proven to use with the
>trigger wire. VW uses such a relay in some vanagons. It costs $62
>This stronger relay was not factory installed in the westy camper
>with the 3 way refrigerator.
>
>This is how I would install the aux. batt. charging circuit, if I
>would use a relay.
>Of course, there are alternative options.
>Note:
>Do not use a relay, that would overload the two trigger wires.
>The relay should be just the right size for the application.
>Not too small and not too big. It should be able to handle
>30 to 40 amps continuously, and not overheat.
>
>This is  how the new battery-cut-out-relay
>should work.
>1)   Engine running: Both batteries are connected. Aux. batt.
>                              and main batt. are charging.
>2)   Engine turned off: The aux. batt. is disconnected from the
>                                  main battery.
>3)   Ignition turned on:  The two batteries are still disconnected.
>4)   Starting the engine:  The two batteries are disconnected.
>
>Nr. 4 is important, since the system discussed is only designed
>to charge the aux. battery, and not for starting the motor.
>VW installed a relay trigger circuit in the camper.
>(Trigger circuit means, it switches relays on and off).
>One can use this circuit for the new batt.-cut-out-relay.
>This will ensure, the batteries are not connected, while
>the engine is started.
>It is located at terminals 85 and 86 on the existing refrigerator
>relay, under the front seat in the westy camper.
>The existing refrigerator-12-volt-heater-relay stays as is.
>We only tap into the two small wires, (terminals 85 and 86)
>to also control the new batt.-cut-out-relay.
>To alter the fridge relay could drain the battery very fast,
>if the engine is not running.
>
>Summary:
>You have to route a new #8 wire from the + on the main
>battery to a breaker, then to a batt.-cut-out-relay, and
>then to the + terminal on the auxiliary battery.
>The new  batt.-cut-out-relay   is triggered by the two
>small wires, on terminals 85 and 86 on the factory installed
>refrigerator cut out relay.
>
>The installation:
>1) Take out the front seats, and gain access to the front batt.
>    boxes. One on each side. Test fit the aux. batt. in its box.
>   If you use a Optima, the terminals should be to the back.
>   You should have enough space on the right side of the
>   aux. batt., to install the new cut-out-relay, and the breaker
>   or fuse.
>   Also mark where to fasten the batt. ground strap to the
>   frame, and mark a place, to drill a hole for the #8 wire.
>   Note the fuel lines, AC hoses etc under the batt. boxes.
>   Take your time.
>
>2) Take aux batt. out and drill the hole for the #8 wire.
>    Remember to use a grommet where it passes through the sheet
>    metal.  Mount the cut-out-relay and the fuse on the right
>   side in the aux. batt. box.
>   I suggest you install a piece of sheet plastic between the
>   new relay/breaker, and the battery box, so the wires later
>   don't rub against the metal.
>   Use the sheet metal screws for fastening.
>   Install  the ground strap to the frame in the batt. box.
>
> 3)Cut two pieces of  # 18 ga wire, and crimp one
>   female connector to each and connect them to the trigger
>   circuit on the  batt.-cut-out-relay.
>   Note:  The new relay should have 4 terminals. The smaller 2
>   terminals should be for the trigger.
>   (one of them might be marked as ground, do NOT ground)
>   Find the 2 small wires that go to terminals 85 and 86 on the
>   refrigerator-cut-out-relay. Look in the Bentley for  the colors
>   of these wires. In the 90 westy they are 1) blue 2) red/black
>   Use two quick-splice-connectors to connect
>   them to the trigger terminals on the new cut-out relay.
>
>
>4)Use the ring terminals to connect the #8 wire.
>   As the wire enters the aux. batt. box, first connect it to one terminal
>   on the 30 amp breaker. Cut a short section, to connect the
>   other terminal on the breaker to one of the big terminals on
>   the new batt.-cut-out-relay.
>   Now connect a long enough section of #8 to the remaining
>   big terminal on the batt.-cut-out-relay. This end goes to the
>   + terminal on the aux. battery. But for now, wrap the end
>   in some plastic, so it does not make ground contact.
>   Make sure the connections on the new relay and breaker
>   don't make any ground contact, and are safe.
>   Use tape, shrink tubing etc. to protect them.
>   Route the #8 wire under the car to the main battery box.
>   Use cable ties to secure it, and make sure there are no
>   sharp objects near the wire. Preferably use a conduit,
>   to give it some added protection. Give the wire lots of
>   slack.
>
>5) Find or make a opening in the main batt. box, to
>   enter the other end of the # 8 wire. Again use a grommet.
>   As an option, you can install a second 30 or 40 amp
>   breaker with the # 8 wire next to the main battery.
>   To reinstall the main battery:
>   Important. Make sure the loose end in the aux. batt. box
>   does not make ground contact. (wrap with insulating
>   tape, or a plastic bag).
>   Now reinstall the main battery, and connect the new #8 wire
>   to the + terminal on the main batt. Leave the ground off, till
>   you are finished on the other side.
>
>6)Install the auxiliary battery.
>   Unwrap the #8 wire, the one that comes from the
>   cut-out-relay, and connect it to the + terminal on the
>   aux. battery.
>   Now connect the ground strap to the - (minus) terminal
>   on the auxiliary battery.
>
>   Go to the other side of the car, and connect the ground on
>   the main battery.
>
>   To test the operation of the relay:
>   Disconnect the new #8 wire at the main battery + terminal.
>   With the engine off, there should be no current and no
>   ground.
>   Reconnect the #8 wire.
>   On the aux. battery:
>   With the engine running, the voltage should be higher.
>   (battery is charging)
>   Engine off, voltage drops.
>
>Note:
>The auxiliary battery compartment in the westfalia camper
>is not vented.
>One should use a sealed battery to prevent the build up of
>fumes. A deep cycle battery will last longer
>and give better service.
>
>      Note: Disclaimer: You should double-check everything
>      with a professional auto electrician. I might have made a mistake.
>      In my own westy, I installed a battery isolator, so I have no
>      long-term experience with the relay setup.
>      But the relay installation is fairly simple and straightforward,
>      and VW installed such a system in some vanagons.
>Maybe some other list members can come up with  alternative
>setups. It would give westy owners more choices for their installation.
>
>Good luck.
>Harald
>90 westy
>