Date: Thu, 13 Dec 2001 14:30:41 -0500
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: Fw: Re: Battery Isolators vs. Relays
In-Reply-To: <019401c18408$20ef6810$3b47fea9@grumpy>
Content-Type: text/plain; charset="us-ascii"; format=flowed
At 01:58 PM 12/13/2001, Julian Burden wrote:
>Ron previously emailed me that the existing fridge relay is a similar but
>different relay to the Hella he sells, and the current limiting factor of
>the cabling is not gained through the fridge relay modification.
Any current limiting has nothing to do with the relay, but rather with the
size and length of the wire connecting the two batteries. It has been
alleged (by someone in the design end of the battery industry who should
have good reason to know) that using 14 ga or so wire will limit charge
current under normal circumstances to fifteen amps or below -- *HOWEVER*
neither he nor anyone else has actually supplied test numbers supporting this.
>Another factor to be considered is the type of battery to be used as the
>second battery. I replaced the main battery soon after I purchased my
>Westie. The old one went under the driver's seat. Regular lead acid
>batteries are not ideal,
Understatement of the decade...starter batteries are meant to be kept fully
charged always, and don't do well when deeply discharged. A battery like
the Optima starting battery that is rated for fifty deep discharges might
be a good compromise -- typical starting batteries probably can't sustain
ten deep discharges.
> but I understand it is hard to get a decent deep
>cycle battery that fits in the space under the drivers seat. Additionally,
>deep cycle batteries should be fully discharged before being charged.
Erm...they last a *lot* longer, like five times as long, if they're 1)
properly charged, almost impossible with a stock automotive setup and 2)
never discharged below 50% except for a few times with a new battery.
> In my
>mind the ideal setup would be a pair of deep cycle batteries with a smart
>controller - $$$$!!!! I think I'll stick with the battery I've got for now.
As you say -- $$$$. And you still have to think about it, even with good
monitoring gear. And the stock alternator may not be up to continuous
high-output operation, so add some more $$$ for a hot-rated alternator. But
if you need the capacity, or the rapid recharge ability, you are going to
end up in this neighborhood sooner or later. Might as well be
sooner. Total costs over ten years might actually come out even or better.
If it were easy we'd all be doing it the same way...
:)
david
David Beierl - Providence, RI
http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"
