Date: Wed, 1 Oct 2003 22:58:30 -0700
Reply-To: mark drillock <drillock@EARTHLINK.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: mark drillock <drillock@EARTHLINK.NET>
Subject: Re: wiring for a 2nd battery
Content-Type: text/plain; charset=us-ascii
You are looking at the wiring diagram for a vehicle you don't have. Look
at page 97.32b instead. That shows the wires to the fridge relay for
81-85. There the power comes in on 87 and goes out on 30. VW reversed
the leads on the aux bat relay from how they wired the fridge relay. If
you add a separate relay for the second battery you could follow either
example. The relay is just a switch that connects 87-30 when it is
actuated. Connecting 30-87 is the same thing. Use a voltmeter and test
87 and 30 first with the engine off and then with it running. The source
lead will have 12 volts all the time and the output lead will only have
12 volts when the engine is running. The second battery needs to connect
to the output lead.
I can explain the reason why they reversed the leads but it does not
really matter and I'm afraid that it may confuse some people. Here goes
anyway. In automotive wiring some things are done certain ways by
convention. That means that whenever a standard part is used it is wired
in a standard way whenever feasible.
By convention, the source voltage should be on pin 30. But VW (or maybe
Westfalia) wanted to share the voltage source with another circuit that
did not go through the relay. Since standard relays were available that
had 2 pin 87s connected together that was what they chose. It was easier
and cheaper to wire the relay in an unconventional fashion. There are no
relays with 2 pin 30s connected together AFAIK. If you look at the
Bentley wiring diagrams you can see dozens of examples of relays with
the source voltage on pin 30 and the output on pin 87. I saw none the
other way except the Westy fridge relay. (I did not check thoroughly) VW
could have had 2 wires to pin 30 as they do on many other pages. That
takes a few extra manufacturing steps so they just reversed the power
leads instead. I suspect Westfalia of this decision as VW is so
conventional elsewhere and Westfalia is unconventional elsewhere in the
Westy wiring. For example, VW uses brown for direct chassis ground
connections but the Westy wiring uses greens and blacks as well as
browns for ground.
Mark
Travers Fenton wrote:
>
> Thanks Mark I'm continuing to read. I'm looking at
> the relay diagram and I think it should be connected
> to post 87 not 30 as per page: 97.34a. Why does the
> vanagon.com say to connect to 30 and you back that up?
> Wouldn't that mean that the positives of the two
> batteries are ALWAYS connected? Don't we want them to
> be only connected when running and not when starting
> or not running.
>
> Confused.
>
> Thanks for your time so far Mark. Hoping that this
> will make it clearer for other people in the future.
>
> FT
> --- mark drillock <drillock@earthlink.net> wrote:
> > You can use relay and still have both batteries get
> > the same charging
> > voltage. This is the simplest way to go as it leaves
> > the original
> > vehicle wiring alone.
> >
> > The Westy fridge relay gets 12 volts from the relay
> > panel which gets it
> > from the main battery. There is a voltage drop due
> > to the long distance
> > and small wire size. Plus when the fridge is running
> > on 12 volts that
> > drops it down even more at the Westy fridge relay.
> > You should verify the
> > voltages with the engine running, first at the main
> > battery positive
> > terminal and then at the red wire of the relay. Then
> > turn the fridge on
> > to 12 volt setting and see it drop even more. The
> > lower voltage will
> > keep the second battery from charging as fully and
> > as quickly as possible.
> >
> > There is plenty in the archives about adding a
> > separate relay for a
> > second battery. I don't have time now to go into it
> > but later I might.
> >
> > Mark
> >
> > Travers Fenton wrote:
> > > I actually have a deep cycle marine battery that I
> > > would like to use heavily. I'm still researching
> > this
> > > but should I use the x switch I've read about.
> > Any
> > > tips or leads on how best to set this up so that
> > it
> > > will get the full voltage of the alternator would
> > be
> > > greatly appreciated.
> > >
> > > Fenton & Jessey
> > > 84 Vanagon
> > > 97 Jetta
> > > --- mark drillock <drillock@earthlink.net> wrote:
> > >
> > >>Yes, use terminal 30 to connect a wire to the AUX
> > >>battery. Be sure to
> > >>put a fuse in the wire. 20 amp should do it.
> > >>
> > >>Leave the existing red wire connected to terminal
> > 30
> > >>also. You can buy a
> > >>tiny splitter that will plug onto terminal 30 and
> > >>give you 2 places for
> > >>wires to connect. Plug the existing wire and your
> > >>new wire into the
> > >>splitter. RadeoShack and many auto parts stores
> > sell
> > >>the splitter.
> > >>$1 should buy 2 or 3.
> > >>
> > >>What you are doing is a common and easy way to add
> > a
> > >>second battery. The
> > >>drawback to this method is that the second battery
> > >>WILL NOT get the full
> > >>charging voltage as seen by the main battery. If
> > you
> > >>use a car battery
> > >>and don't need to use it heavily it should work
> > fine
> > >>and many have done
> > >>it this way.
> > >>
> > >>Mark
> > >>
> > >>Travers Fenton wrote:
> > >>
> > >>>I have an 84 Westfalia that I'd like to set up so
> > >>
> > >>that
> > >>
> > >>>the alternator charges the auxiliary battery. I
> > >>>believe I have the relay that some articles said
> > >>
> > >>was
> > >>
> > >>>usually included. I found a 5 connector relay
> > >>
> > >>under
> > >>
> > >>>the drivers seat. Three wires are coming from
> > the
> > >>>front, a blue one connected to 86 on the relay, a
> > >>
> > >>red
> > >>
> > >>>one connected to 30 on the relay and a red one
> > >>
> > >>with a
> > >>
> > >>>black stripe connected to post 85 on the relay.
> > >>
> > >>Then
> > >>
> > >>>I have two red wires heading into the back, one
> > is
> > >>>connected to post 87 and the other is connected
> > to
> > >>
> > >>the
> > >>
> > >>>center post. The posts are in a cross formation.
> > >>>
> > >>>Now following 6 steps in the directions on
> > >>
> > >>vanagon.com
> > >>
> > >>>for setting up a second battery it says ( in step
> > >>
> > >>4 )
> > >>
> > >>>to connect terminal #30 to the positive terminal
> > >>
> > >>of
> > >>
> > >>>the auxiliary battery.
> > >>>
> > >>>My question is, should I also leave what is
> > >>
> > >>already
> > >>
> > >>>connected to the #30 terminal on the relay and
> > add
> > >>
> > >>the
> > >>
> > >>>auxiliary battery to this connection or should I
> > >>>disconnect this wire from the #30 and replace it
> > >>
> > >>with
> > >>
> > >>>the connection to only the positive on the aux.
> > >>>battery?
> > >>>
> > >>>Is this indeed the relay that is factory
> > installed
> > >>
> > >>in
> > >>
> > >>>many westy's? Some of the numbers on this relay
> > >>
> > >>are:
> > >>
> > >>>411915511B & SR9813. 12Vmax30A.
> > >>>
> > >>>Thanks in advance.
> > >>>
> > >>>Fenton & Jessey
> > >>>84 Vanagon
> > >>>97 Jetta
> > >>>
> > >>>__________________________________
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> > >>
> > >
> > >
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> >
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>
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