Date:         Mon, 22 Sep 2003 07:21:16 -0700
Reply-To:     Roger Donahe <rdonahe@COMCAST.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Roger Donahe <rdonahe@COMCAST.NET>
Subject:      Re: Mystery part - what is this thing?
Comments: To: laurasdog@weirdstuffwemake.com
In-Reply-To:  <000001c37feb$b5a64240$6201a8c0@Dee>
Content-Type: text/plain; charset="US-ASCII"

Hey thanks Steve.

I'm getting 13.75 or so volts at the primary battery when running, and
13.03 at the secondary. Is this sufficient for recharge? It has been so
far but I've only had the van for a month.

So if I want to leave the isolator in place, and get that secondary
battery to power my house lights, do I run a lead from the secondary
battery terminal on the isolator to the fusebox behind the drivers seat?
Or simply from the positive terminal on the secondary battery? I'm
guessing I can run it directly from the secondary battery as the
isolator should be only for the charging system. Am I understanding this
setup correctly?

-Roger

-----Original Message-----
From: laurasdog@weirdstuffwemake.com
[mailto:laurasdog@weirdstuffwemake.com]
Sent: Saturday, September 20, 2003 6:43 PM
To: Roger Donahe
Subject: Re: Mystery part - what is this thing?


At 06:01 PM 9/20/2003 -0700, you wrote:

>http://rodo.shacknet.nu/pix/2003_09_20/118_1867.jpg
>http://rodo.shacknet.nu/pix/2003_09_20/118_1870.jpg
><snip>

It's a battery isolator. It's basically 2 large diodes, connected anode
to anode.

Typically one terminal goes to the charging system
(output of alternator), one terminal goes to the main
battery and one goes to the 2nd (house) battery.
It allows the alternator to charge BOTH batteries, but
keeps the batteries isolated from each other.

It's used in place of the "charging relay" that's
typically used in Westy's. The main problem
with the battery isolators is that they introduce an aproximately 0.7
volt drop in the charging voltage which is bad because the output
voltage of the Vanagon alternator borders on being to low already.

This can be cured by adding an external voltage
regulator to the stock Bosch alternator.

If you are willing to modify your alternator for a
higher charging voltage, then you should you the
battery isolator, which is superior in several ways to
using a relay.

If you don't want to mod your alternator, then use
the relay setup and remove the battery isolator...

Steve
EJ22 -> '86 Westy "Escape Pod"