Date: Sun, 31 Jan 1999 18:35:24 -0800
Reply-To: Davidson <wdavidson@THEGRID.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Davidson <wdavidson@THEGRID.NET>
Subject: Re: Dual Battery Relay - Part 2 (long)
Content-Type: text/plain; charset="iso-8859-1"
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
>
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