Date: Tue, 11 Dec 2001 23:15:09 -0500
Reply-To: Dennis Haynes <dhaynes@OPTONLINE.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <dhaynes@OPTONLINE.NET>
Subject: Re: Battery isolator
In-Reply-To: <008401c182a5$8d78bf40$6601a8c0@vista1.sdca.home.com>
Content-type: text/plain; charset=us-ascii
What battery isolator comes in which model camper? The relay under the
drivers seat in a Westy Vanagon is wored to disconnect the refrigerator
circuit when the alternator is not charging. The blue wire is connected
to the alternator warning light circuit. When the alternator is
charging, it actually powers the relay. For some reason, they wired the
ground to the starter solenoid circuit. I guess this is to disable the
relay during engine starting. Of course, it would be unlikey that you
would have alternator output while cranking the engine. Anyway, the ble
wire is an ideal source topower a larger relay to chrge the auxiliary
battery. Since it will power the relay only when the alternator is
operating, there is no need to worry about one battery discharging into
the other. You also don'y need wiring heavy enough to support the
starter as would be needed if energizing the relay off the ignition
switch.
Dennis
-----Original Message-----
From: developtrust [mailto:developtrust@home.com]
Sent: Tuesday, December 11, 2001 7:40 PM
To: Dennis Haynes
Subject: Re: Re: Battery isolator
Are you suggesting to replace the one that comes in the camper with
relays
to isolate-charge the "house" battery? I have not hooked up my Optima
yet
but soon will and I see my auxiliary battery box has a relay of sorts in
it
now. Will this suffice or should I consider replacing it?
William Polowniak
----- Original Message -----
From: "Dennis Haynes" <dhaynes@OPTONLINE.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, December 11, 2001 3:54 PM
Subject: Re: Battery isolator
> Normal battery isolators are a poor choice in a VW due to the forward
> voltage drop. All power diodes drop over 1.0 volt when cool. As they
> heat up, the drop increases. The vw senses and control the alternator
> output internally so this drop is not compensated. Only 11.5 to 12
volts
> actually charges the battery. Many American cars sense and control the
> charging voltage remotely so the alternator output will increase to
> overcome the resistance. The alternator can be modified to overcome
> this. I feel it is not worth the effort. Virtually every RV
manufacturer
> uses relays to isolate-charge the "house" battery(ies). It is simple,
> reliable, and low cost. It is also more efficient as you do not have
the
> heating effect with a relay.
>
> Dennis
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
Behalf
> Of Julian Burden
> Sent: Tuesday, December 11, 2001 2:11 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Battery isolator
>
> I was told that a regular battery isolator will not work in a Vanagon
by
> someone who was told by someone who . . .
>
> I did not believe this as my understanding is that a battery isolator
is
> just a pair of diodes on a big heatsink.
>
> But, then I looked at the JC Whitney website catalog - they list
several
> isolators, many of which are described as not suitable for all VW
vans!
>
> Why is this so, and what do I need?
>
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