In a message dated 09/05/2004 12:09:22 AM Eastern Daylight Time,
LISTSERV@GERRY.VANAGON.COM writes:

I'm  curious as to what voltages would be normal for 2 batteries w/ a
surepower  isolator.  My main battery seems to have bitten the dust, I
killed it  leaving the "headlights" (the parking lights, etc which remain
on after  engine is turned off) on overnight.  The battery would take no
charge  at all, I could start it from the aux battery, but it would take
no charge  at all, after an hour of engine running.  So today I installed
a new  battery, and things seem ok, for the moment.

My alternator puts out  13.8v.

Each of the batteries, with engine on, read 12.8 -  12.98

As I understand it, the voltage should be OVER 13 while engine  is
running.  Engine off, the batteries are at 12.6 or 12.7

So  the isolator is giving them each a little extra voltage, but not as
much as  I would expect.  I am fairly new to DC electricity in vehicle
context,  so if anyone can help me test to make sure my isolator is set
up properly,  and my alternator is working correctly, I would appreciate
it.  I'm  reading "Managing 12Volts", which is a great book, but its
basically  telling me I need to measure evertying at 80 degrees.

I'm paranoid that  I screwed up the isolator install somehow, and the
batteries are just  slowly draining (the install was a month ago, and
things seemed  ok).

Rob, I've got pretty much  the same set up you have so my info may be of use
to you.  I don't see what  you aux battery is but mine is an Optima Yellow
Top.  Standard group 41 as  main battery and the Sure Power battery isolator.  I
have installed a  digital voltmeter connected to the two batteries with a
switch so I can check  either of the two anytime I want by flipping the switch.
Readings I get  normally are exactly what your getting.  With motor running and
only the  radio/CD player back lights and digital dash clock on the aux
battery I get  between 13.3 ~ 13.9 on both batteries.  With engine off I see 12.5
to 11.5  depending on the battery and time the engine has been off.  There is
nothing running off the main battery with engine off and only radio/CD back
lights and digital dash clock on the aux battery.
Cheers,

Frank  Condelli
Almonte, Ontario, Canada
_BusFusion_ (http://members.aol.com/BusFusion/bfhome.htm)  a VW Camper
camping event, Almonte, ON, June 10 ~ 13, 2004
'87 Westy & Lionel  Trains
Member: _Vanagon List_ (http://www.vanagon.com/) , _LiMBO_
(http://www.bcn.net/~limbo/) , _IWCCC_ (http://www.westfalia.qc.ca/)  & _CCVWC_
(http://www.ccvwc.ca/)
Vanagon/Vanagon Westfalia Service in  the Ottawa Valley
_STEBRO/Vanagon Stainless Steel  Mufflers_
(http://members.aol.com/Fkc43/stebro.htm)
_Frank Condelli &  Associates_ (http://members.aol.com/Fkc43/busindex.html)
or  http://frankcondelli.com