Anyone considering an isolator might want to look into a Battery Combiner.

They are sold by West Marine. I believe they claim no voltage drop across
them like isolators. And my impression is that virtually everything marine
is superior in quality to automotive stuff.

West Marine has a tech department that you can talk with. The 50A model
143268 is listed in their catalogue for 59.99... www.westmarine.com
Bill

----- Original Message -----
From: "harald_nancy" <harald_nancy@earthlink.net>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Monday, June 19, 2000 4:05 PM
Subject: Re: Becketts Tome on Dual Batt.s,Relays,Saftey,and charging (Very
Long)

> Dan
> 1) I would start by making sure that the alternator on the '82 vang.
> is in good shape. Take it out and find an automotive electrical shop
> that rebuilds Bosch alternators, starters etc. Pay them a small fee
> to have the alternator tested. The alternator should always be
> in top condition (especially the smaller 65amp alt. on the '82)
> to work properly with the isolator. If it has more than a 110 thou.
> miles on it, have the shop install new bearings and consider a
> new regulator, to make sure you get the highest voltage possible.
> The alt. has to work harder with the isolator.
> I had much better successs rebuilding my orig. alternators than
> buying  rebuilt ones. I put new brushes and bearings in mine every
> 110 thou.miles.
> I don't know what brand isolator you are using.
> It could be a Sure Power 702R up to 70 amp, or
> 952R up to 95 amp or 1202R up to 120 amp.
> The R stands for Remote regulator sensing. This terminal is
> supposed to be connected to the regulator in the following
> manner: (if that is what you got)
> 2) Alternator does not need to be removed. Just unscrew the
> regulator ( that black thing with the little round disc) and
> take it out. ( be careful with the brushes)
> Bend over the metal tab that contacts
> inside the alt. ( bend it all the way up)
> and solder a # 14 wire to it.
> Push the contact prong inside the alt. a bit more in, to
> make sure it won't make contact. Reinstall regulator.
> That wire goes to the R terminal on the isolator.
> Now the alternator can compensate for the 0.8 volt
> voltage drop across the diodes.
> 3) How old is the isolator? I don't know if the diodes
> in the isolators become less efficient with age,
> but they can burn out. Just like everything else.
> If the isolator is 18 years old, I would replace it or
> at least, test it. They are not that expensive.
> The 952R I think is $ 40 to 50. Good for the
> 65 amp alternator. If you have the 90 amp alt.
> use the 1202R for longevity.
> If an isolator fails, (burns out) it can connect both
> batteries, and charging efficiency will be reduced,
> and also both batteries will be discharged when
> using camping appliances (12 volt).
> 4) The batteries could also be less efficient from
> age or use.
> or it can be a combination of all of the above.
> Harald
> 90 westy
>
> ---------
> > From: Daniel Schmitz <djs@gene.com>
> > To: vanagon@GERRY.VANAGON.COM
> > Subject: Re: Becketts Tome on Dual Batt.s,Relays,Saftey,and charging
> (Very Long)
> > Date: Sunday, June 18, 2000 11:52 PM
> >
> > Related to this thread, I have an isolator on my '82 Adventurewagen. It
> used to
> > work well, but I noticed that in the last several years, the voltage
drop
> across
> > the alternator terminal and either of the charging terminals is such
that
> my
> > batteries aren't always getting enough voltage to charge properly.
> >
> > Couple with this, I never did use that 4th, smaller terminal on the
> isolator. Is
> > that the alternator sensing terminal, and if so, what should it be wired
> to?
> >
> > Currently I'm bypassing the isolator so my battery always gets a good
> charge.
> >
> > ...Dan
> >
> > Beckett Cantrell wrote:
> >
> > > Harald, please forgive me if I seemed to insinuate that batt.
isolators
> were
> > > no good. Some work wonderfully, the key being the remote sensing
> terminal you
> > > mentioned. I aimed the previous posts at relay switched dual batt.
> charging
> > > systems as they are much more common and inexpensive than the isolator
> > > methoud.
> > > Good luck,
> > > Beckett
>
>
> ----------
> > From: Daniel Schmitz <djs@gene.com>
> > To: vanagon@GERRY.VANAGON.COM
> > Subject: Re: Becketts Tome on Dual Batt.s,Relays,Saftey,and charging
> (Very Long)
> > Date: Sunday, June 18, 2000 11:52 PM
> >
> > Related to this thread, I have an isolator on my '82 Adventurewagen. It
> used to
> > work well, but I noticed that in the last several years, the voltage
drop
> across
> > the alternator terminal and either of the charging terminals is such
that
> my
> > batteries aren't always getting enough voltage to charge properly.
> >
> > Couple with this, I never did use that 4th, smaller terminal on the
> isolator. Is
> > that the alternator sensing terminal, and if so, what should it be wired
> to?
> >
> > Currently I'm bypassing the isolator so my battery always gets a good
> charge.
> >
> > ...Dan
> >
> > Beckett Cantrell wrote:
> >
> > > Harald, please forgive me if I seemed to insinuate that batt.
isolators
> were
> > > no good. Some work wonderfully, the key being the remote sensing
> terminal you
> > > mentioned. I aimed the previous posts at relay switched dual batt.
> charging
> > > systems as they are much more common and inexpensive than the isolator
> > > methoud.
> > > Good luck,
> > > Beckett
>