Date: Sun, 5 Aug 2007 21:12:01 -0700
Reply-To: Reinhard Vehring <rvehring@YAHOO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Reinhard Vehring <rvehring@YAHOO.COM>
Subject: Re: T3 Westy's; batteries; how to have your cake and eat it
In-Reply-To: <e3e1d7f0708052009h31c697f9r80854761f7026abb@mail.gmail.com>
Content-Type: text/plain; charset=iso-8859-1
Good point about the cutoff point, Martin.
I am not sure though that I would be comfortable
emptying half of my starter battery. The starter has a
hard time getting the 2.3 l turned over sometimes even
with a full battery. Wonder why, maybe I should have
upgraded the size of the wire to the starter when I
did the conversion or it's the lower cranking amps of
the yellowtop.
Have fun,
Reinhard
83 "Half-Syncro" Westy, Moose
--- Martin Jagersand <jag@CS.UALBERTA.CA> wrote:
> The sure power's are also voltage triggered relays,
> but specs say they
> cut out at 12.8V. (www.*sure**power*.com), unless
> you manage to somehow
> adjust the voltage breakpoint (this option was not
> mentioned on the web
> site).
> No load, full charge voltage of a 12V lead-acid is
> 12.6-12.7V. A 12.8Vcut-off
> voltage means you won't effectively draw camping
> power from both batteries.
> ie two 70Ah batteries isolated with a surepower
> gives 70Ah for camping,
> while
> two isolated with an isolator with a relay with a
> 12V breakpoint gives 100+
> Ah
>
> Useful voltage breakpoints for two 12V deep cycle
> batteries in parallel
> are probably in the range from 12 - 12.4V. With a
> 12V relay, one can raise
> the cutoffpoint to 12.2 V by putting a shottky diode
> in forward series with
> the
> sense wire; 12.4 V with two etc, but it is not so
> trivial to lower the
> cutoffpoint
> point witout access to the internal circutry, unless
> this has been explictly
> provided for in the design.
>
> The "battery protector" I got will always charge
> both batteries in parallel,
> while the sure power will start the bulk charge of
> one first, then the
> other.
> The former is quicker if one has a powerful
> alternator, while
> the latter is maybe a bit milder on the alternator.
> I've had old 65A
> alternators cut out on the older vans due to
> overload. I don't
> have any problem with my 120A alternator even with
> the 3 battery setup I
> put in the '94 Westy.
>
> At the $27 Canadian tire sale price I thought I got
> a good deal.
> Hopefully quality is at least decent. CT puts their
> own labels on
> a lot of OEM stuff. Some is good quality, some not.
> So far I have
> had good luck with the electrical stuff. (e.g. most
> of their inverters
> are actually relabeled Xantrex, a well known brand.)
>
> Martin
>
> On 8/5/07, Dennis Haynes <d23haynes57@hotmail.com>
> wrote:
> >
> > You went through a lot of trouble to basically do
> what a battery combiner
> > or smart relay such as the sure power 1315 does.
> The sure power uses a
> > wide range so that after cut out at 12 volts, it
> will not cut back in
> > until one of the banks gets up to 13 volts which
> would indicate a charge
> > source is now there. This set up arks great even
> with a conventional
> > strting battery combined with deep cycles.
> >
> > Dennis
> >
>
>
> --
> Martin Jagersand
> University of Alberta
> http://www.cs.ualberta.ca/~jag/
>
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