Only a isolator device that senses the charge state of the batteries
individually AND applies a different charging voltage to each battery as
needed can do a better job. The cheaper isolators, and the $120 system
was a cheaper one when I last checked, do not have this capability. They
only sense one battery and aply the same charging voltage to both. For
this reason, they should be connected so as to sense the state of the
main battery. The aux. battery will suffer a shortened life as a result
but you are less likely to be stranded.

Mark

Bulley wrote:
>
> What do you mean by "better job of charging both batteries"?
>
> The reason I ask is that the isolator and fittings for futzing with the
> Bosch alternator to force it to work with an isolator came to more than
> $120, while the solenoid was $18. How much 'better' can batteries be
> charged?
>
> G. Matthew Bulley
> Director
> Bulley-Hewlett & Associates
> www.bulley-hewlett.com
> Cary, NC USA
> 888.468.4880 tollfree
>
> -----Original Message-----
> From:   Mark McCulley [SMTP:transporter99@HOTMAIL.COM]
> Sent:   Wednesday, November 03, 1999 10:23 AM
> To:     vanagon@GERRY.VANAGON.COM
> Subject:        Re: Is battery isolator better than a relay?
>
> >I have heard that some folks have located the remote sensing connection in
> >the alternator regulator and added a wire to remote sense.
> >
>
> The SurePower isolator is designed to be connected to remote sense for the
> voltage regulator. This requires a modification to the regulator, but it's
> not very hard to do.
>
> >The good news is that the relay is not as bad as it first sounds.  Lead
> >acid batteries have charging characteristics that allow them to charge in
> >parallel and share the charging current fairly well.  And, connecting a
> >discharged battery across a charged one isn't all that dramatic either.
> >  Again, they quickly adjust to one another and as long as you drive long
> >enough to charge the low battery there should be no problem.
>
> I've used both approaches and the isolator definately does a better job of
> keeping both batteries fully charged.
>
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