Date:         Thu, 22 Jun 2000 18:12:51 -0400
Reply-To:     Tom Moritz <tmoritz@bmi.net>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Tom Moritz <tmoritz@bmi.net>
Subject:      Auxillary batter - isolation device
Content-Type: text/plain; charset="us-ascii"

I know that there has been extensive dialog about auxillary batteries and
methods of isolating the aux battery from the starting battery but I
thought I should put this out there anyway.  As I was researching the
suggestion for battery isolators manufactured by Sure Power Industries,
Inc. I noticed they had a product they referred to as battery separators.
This is a device that is connected between the positive terminals of the
two batteries.  It evidently has some solid state electronics to measure
the voltage of the battery being charged.  Once this voltage exceeds 13.2V
it closes the contact between the batteries and starts to charge the
auxillary battery in parellel.  If the current requirements are greater
than the alternator can produce the separator will disconnect the batteries
thus directing all the available charge to the battery directly connected
to the charging source.  The system will then reset and reattempt to
connect the batteries once the voltage exceeds 13.2V.  Evidently it even
has a time delay to prevent rebounding either on connection or disconnection.

This separator also has a start assist feature.  This is an optional input
that allows the operator parallel the batteries for starting if there is
enough power available in the auxillary battery.  The contacts on the
separator are rated at 400A momentary 100A continuous.

I've just ordered the model 1315 battery separator from a local distributor
and will be installing it along with a recently purchased Optima D900M, a
12V marine version of the D750S.  I plan to interconnect the batteries with
size 4 starter wire as I want to be able to use the start assist feature if
necessary.  I plan to wire in a momentary lit rocker switch which will
activate the start assist.  I plan to light the switch using the start
assist lamp output which shows the auxillary battery has sufficient power
for starting assistance.

If you want more information regarding these devices you can consult Sure
Power's web page at http://www.surepower.com .  If there is interest I will
report back regarding my progress as I make these changes.  Phase two
involves installing a battery meter from Cruising Equip. Inc., fuse block,
extra interior lighting, and connecting devices like fridge, water pump,
lights, and stereo to the fuse block.

I'll welcome your feedback.

Tom Moritz
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