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Date:         Tue, 21 Sep 2004 11:01:54 -0700
Reply-To:     Fin Beven <FinBeven@MSN.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Fin Beven <FinBeven@MSN.COM>
Subject:      dual battery isolator / Optima Batteries
Comments: To: Dennis Haynes <dhaynes@OPTONLINE.NET>
Content-Type: text/plain; charset="iso-8859-1"

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.


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