Date:         Sat, 29 Sep 2007 11:09:59 -0300
Reply-To:     David Etter <detter@MAIL.AURACOM.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Etter <detter@MAIL.AURACOM.COM>
Subject:      Re: New fridge replacement option for the Dometic
In-Reply-To:  <vanagon%2007092821414344@GERRY.VANAGON.COM>
Content-type: text/plain; charset=us-ascii; format=flowed

Hi Warren:
        Just be careful that these Wheelchair Batteries when parallel
linked require special charging technology. They cannot be charged by
the usual direct alternator input. They require a much lower and
slower charge rate and will overheat and die an early death if
charged at normal battery rates.
        I was planning the same 4 - 6 battery system until I read the
charging requirements. I'm not saying it can't be done, it's just
that you would have to arrange another layer of "jiggery pokery"
(technical term for fiddling around) in the Westy system.
        If you ask someone who regularly uses these batteries you
will find that they traditionally plug them in for overnight charging
on a 2- 3 amp 'brick' style adapter.
Good Luck and if you do come up with a good satisfactory SIMPLE
system , please let me know as I still believe that the small 12 volt
Wheelchair batteries are a good idea.

Regards!
                                                David
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


>Karl,
>
>This looks identical to the "Isotherm CR65" unit I bought a few months
>ago.  I first saw one of these in Eric Abercrombie's Syncro at Syncro de
>Mayo a few years ago.
>
>It's a little shorter than the Dometic but volume is much better due to
>extra depth.  2.3 cu ft. I believe.
>
>I think you may be a little optimistic about how long it will run on a
>given battery charge though....unless you've had it in long enough to test
>it in actual use.  "4 days" seems very optimistic.
>
>The Danfoss compress draws a max of 2.7 amps. I "bench tested" mine with
>some food inside and based on how often it cycled I estimated it would use
>somewhere between 18-22 amp hrs daily. It ran a used but charged, starting
>battery we had around to "dead" in about a day and a half.  I estimate
>that the popular 55ah Optima...if drawn down to 50% of its capacity (to
>preserve life), or 27.5 amp hrs useable, would only last about a day and a
>half.
>
>Seems we will need more deep cyle battery capacity...or supplemental solar
>charging for a weekend camp out.
>
>A few months ago Mark Drillock and I were discussing use of several 22ah
>wheelchair batteries linked in series.  Only 2.9" wide and 6.8" tall, four
>would fit under the driver's seat for 88hrs, enough for 2+ camping days.
>Mark plans a bank of six in a tray under the van near the sliding door.
>I'm considering 4 more in the engine bay....I want to avoid the expense
>and hassles of solar charging.
>
>Some of these wheel chair batteries can be drawn down to 80% of capacity
>instead of 50% and recharging life will be reduced, but the
>reduction ...to something like 225 re charges...instead of 500...seems
>like something I can live with..(at the number of trips I take
>annually)....for the benefit of the extra useable amp hours.
>
>What's your real world experience been like?
>
>Warren C.