Vince,
I agree, I had a deep cycle model battery in the drivers well and had it
linked at the starter post to the whole system
the two batteries went bad in about two years, I believe they were
constantly working against each other. Especially when sitting for long
periods.

The factory relay is so simple, I dont know why folks feel the need to not
use it.

Doug

----- Original Message -----
From: "Vince S" <gipsyflies@COMCAST.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, September 21, 2004 11:47 AM
Subject: Re: dual battery isolator / Optima Batteries

> Using stainless screw to bridge the gap is not the best solution.
> Stainless steel is not exactly known for good electrical characteristic.
> It has very high resistance. This is especially of a concern with the
> staring battery. Starter draws upwards of hundred amps and the tiny
> contact surface may get so hot that may even melts the lead around it. I
> don't recommend performing the top posts removal of the Optima for the
> starting battery due to such high current demand unless you can
> reconstruct the gap with a very high power soldering iron.
>
> Combining two batteries of exactly the same brand, model, and age may
> work well in most situations but I won't preach it like a gospel. It is
> not a recommendation any reputable battery manufacturer would recommend.
>
> Why not just go with the Westfalia intended relay isolation for a house
> battery and the starting battery? Simple, safe, and effective.
>
>
>
> - Vince
>
> http://gipsyflies.home.comcast.net
> 1989 Vanagon GL Camper
> 1993 Mazda Miata (for sale)
> 1996 Land Rover Discovery
> 2005 Mini Cooper S
>
>
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
> Of Fin Beven
> Sent: Tuesday, September 21, 2004 11:02 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: dual battery isolator / Optima Batteries
>
>
> The simple solution is to just combine the two batteries.  Use large Ga.
> wire (2 ga, minimum).  But I believe that it is important that the
> batteries be identical.  The result is ONE BIG BATTERY.
>
> To complete the system, add a good volt meter.  JC Whitney sells a LED
> panel-mount voltmeter which seems reasonably accurate, and which can run
> all night while using virtually zero amps.  (I actually have an
> on-off-on switch on mine, allowing it to operate when the ignition is
> on, or directly from the batteries).  It actually makes a rather nice
> "night-light" at night.
>
> The system is not idiot proof.  It requires that you actually look at
> the volt meter occasionally if you are using significant equipment (like
> watching a DVD on a computer being powered by an inverter).  Depending
> on the particulars of your starting system, you should still be able to
> safely start and re-charge with "at-rest" votage that has dropped to the
> 11.5 range.
>
> Optima Batteries:  This one is not for the faint-of-heart.   I decided
> that I would prefer to install them in the up-right position, but this
> would involve cutting off the top-mounted terminals and attaching to the
> side-mounted screw-in terminals.  I looked at the renderings of the
> Optima Batteries on their website.  It appeared that the top-mounted
> terminals were a solid piece, such that cutting them off should be no
> problem.
>
> Not So, at least not exactly.
>
> When I cut off the negative terminal of the first of my two new "yellow
> tops" I noticed that the terminal was, in fact, not quite solid.  It was
> as if there was an inner core (about 1/2 of the overall diameter) and an
> outer ring. There was a very small gap between the core and the outer
> ring.  And I now had ZERO voltage at the screw-in terminals.  After some
> brief testing (this only seemed to matter on the NEGATIVE terminal) I
> determined that there was insufficient contact beteen that inner core
> and the outer ring.  Believing that I may have destroyed the battery,
> and further believing that I had little to lose, I screwed a #4 x
> 3/8ths" stainless steel pan-head/phillips head screw into that very
> small gap between the core and the outer ring.  This seemed to force the
> inner core into better contact with the outer ring.  Happy with by my
> results, I inserted another screw along-side the first, just for good
> measure.  I then completed the same operation on the #2 battery.
>
> After a week of camping in the Lake Tahoe / Blue Lakes area that ended
> with snow on Saturday morning, I'm satisfied with the results, and with
> the Optima Batteries.  The installation looks like it was "meant-to-be",
> and I detected no lack of voltage using the side terminals.  This may be
> especially so because I'm using the two batteries.
>
> Fin Beven
> '90 Carat, Custom Camping Conversion
> Pasadena, CA
>
>
>
>
>
>   ----- Original Message -----
>   From: Dennis Haynes<mailto:dhaynes@OPTONLINE.NET>
>   To: vanagon@GERRY.VANAGON.COM<mailto:vanagon@GERRY.VANAGON.COM>
>   Sent: Sunday, September 19, 2004 8:07 AM
>   Subject: Re: dual battery isolator
>
>
>   If not a defect, then either you are getting a false reading or the
>   advertising is misleading. I have seen regular isolators drop that
> much
>   voltage but I was being conservative and my experience shows the 1.1
> to
>   be normal until things really heat up. Anyway, thanks for proving some
>   of my points.
>
>   Dennis
>
>   -----Original Message-----
>   From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
> Behalf
>   Of Gnarlodious
>   Sent: Saturday, September 18, 2004 9:10 PM
>   To: vanagon@GERRY.VANAGON.COM<mailto:vanagon@GERRY.VANAGON.COM>
>   Subject: Re: dual battery isolator
>
>   Entity Dennis Haynes spoke thus:
>
>   From 23 Aug 2004
>
>   > after they get warm the actual voltage drop is closer to 1.1 volt.
>   Well, I just installed the Hellroaring model BIC-95150B and I am
>   dismayed to
>   se a 1.4 volt drop across the switch at ambient temperature.
>
>   At $174.45 for the high technology and much touted product this is
>   disappointing. The specs page didn't mention voltage drop. I'll try to
>   communicate with them about it during the week, maybe it's a defect.
>
>   -- Gnarlie
>
>
>    At 90 amps, the isolater is dissapating almost 100 watts. This is why
>   they
>   need heat sinks. You are paying for this power. Now, with this voltage
>   drop,
>   you are getting less than 13 volts to the batteries and accessories.
> Ok,
>   so
>   now you can modify the regulator to increase the voltage or use a
> remote
>   sense wire to compensate. At full load the limiting factor of an
>   alternators
>   capacity is its own resistance. Thus at full load, it is only slightly
>   more
>   than 50% efficient. Yes, 1/2 the power produced is given off as heat
> in
>   the
>   alternator itself. That is why they have a big fan and they still get
>   hot.
>   So, we increase the voltage of the alternator by 1.1 volt so at 90
> amps
>   the
>   alternator dissipates an additional 100 watts of heat. Can we say
>   shorter
>   life? So at full load, we are wasting ~200 watts of power due to the
> use
>   of
>   the isolator. Under ideal conditions, 1 HP = 746 watts. Not that you
>   will
>   notice but we are wasting .26 HP here. The big issue here is the load
> on
>   the
>   alternator.