Date:         Thu, 10 Aug 2000 19:40:55 -0700
Reply-To:     harald_nancy <harald_nancy@earthlink.net>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         harald_nancy <harald_nancy@earthlink.net>
Subject:      Re: Battery isolator vs combiner??
Content-Type: text/plain; charset=ISO-8859-1

Ken,
I called Sure Power a few months ago, and they also told me
that their isolator is more efficient than their combiner in the
vanagon application.
The technician claimed that the combiner is actually less
efficient, because of the power loss across the contacts.
(They would make more money selling combiners.)
Makes you wonder about relays.
I've been using Sure Power isolators in different vanagons,
'81 air cooled and '90 model, for many years.
For me, the SP isolator works very well in the vanagon
installation.
Here are the voltage measurements I get on my '90 westy
with the 90 amp alternator.
Engine compartment:
voltage at alternator:             14.84
voltage at battery 1 terminal: 14.14
voltage at battery 2 terminal: 14.14

Front of the vanagon:
voltage at aux. battery:          14.2
voltage at main battery:         14.2
voltage at outlet in dash:       13.95

That's with a 1 year old Bosch regulator, and had my original
alternator rebuilt by a local shop.
You can see how the voltage drops on its way to the dash.
When I turn on the headlights and other accesories, the
voltage drops even more at the dash, all the way down
to close to 12.5 volts, in extremes.
But that's because of the wiring in the vanagon.
At the battery terminals, the voltage stays around 14.2.
Overall, these measurements are very acceptable to me.
I never have any dead battery or charging system problems.

It might be somewhat more marginal with the 65 amp
alternator on the older models. But I've previously used the
SP isolator on my '81 vanagon, and it did ok.
The 65 amp alternator has to be in good condition to keep two
batteries charged, and the batteries also have to be in good condition.
I don't know how it would work with a 45 amp alternator (diesel??).
Looks like you have a diesel westy.
I think the isolator works very well with the 90 amp alternator,
and both batteries last a long time (like 6 yrs +).
The Sure Power model that I'm using is 1202R.
Good luck.
Harald
'90 westy

Ken wrote:
> Being in the mood to install a 2nd battery in my 82 Westy, I have been
> reading the archives about the SurePower isolator and the more recently
> mentioned combiner. The drawback to the isolator I had assumed to be
about a
> .7 volt loss in charging and some modification to the alternator
regulator.
> The battery combiner seemed to be the ticket as it didn't have these
problems
> and in addition could (optionally) be used to combine the 2 batteries for
> emergency starting. The SurePower people tell me, however, that for
Vanagons
> the best choice is the isolator and that the supposed .7 volt charging
loss
> is actually compensated by increasing the charging rate the same amount.
Also
> the isolator being solid-state would last longer and be more trouble free
> than the electo-mechanical combiner besides being half the cost.
> Looking at the West Marine catalog the isolator again is mentioned as
losing
> that .7 volt and not being the best way to go.
> I am probably going to use a deep cycle lead acid battery until I can
afford
> the spiral-wound or gel cells. What am I missing here? Is the isolator
OK?
>
> Ken Hunter
> 82 Westy 1.9D
> 84 Jetta 1.5D
> 89 Mitsubishi van