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Date:         Tue, 20 Jun 2006 13:46:21 -0400
Reply-To:     dhaynes@OPTONLINE.NET
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dennis Haynes <dhaynes@OPTONLINE.NET>
Subject:      Re: Understanding Amp Hours
Comments: To: Dave Vickery <davevickery@HOTMAIL.COM>
In-Reply-To:  <BAY101-F766A8A0C1B4DD27B61BC8A0870@phx.gbl>
Content-type: text/plain; charset=us-ascii

The 650CCA has nothing to do with the long term discharge capacity. It is a rating of how much current can be delivered for 30 seconds at 0F and still maintain 10.5 volts. Typically, this battery is rated at ~65 A/H total capacity. As the voltage of the battery starts falling, it is no longer delivering 8 amps into the heating element. Also, since this battery is not designed for this, after a few cycles, damage has been done to the plates and capacity is permanentley lost. At some point the deformed plates will short out in a cell causing you to have a 10 volt battery. Then you will get that great acid boil over as the alternator pumps current into that 10 volt battery and overcharges the remaining cells. For the event of a charging system failure, these batteries do have a "reserve capacity" rating. This is a rating of how long the battery can support a 25 amp load so you can drive home or to get help.

Dennis

----- Original Message ----- From: Dave Vickery <davevickery@HOTMAIL.COM> Date: Tuesday, June 20, 2006 12:58 pm Subject: Re: Understanding Amp Hours

> A real world example. A new Sears diehard 650 CCA aux battery > will last 4 > hours until completely dead running the 8 AMP fridge. On 12 V the > fridgeruns continously pulling 8 amps. So assume 50% depletion in > 2 hours = 16 > Amps available. > > > >From: Loren Busch <starwagen@GMAIL.COM> > >Reply-To: Loren Busch <starwagen@GMAIL.COM> > >To: vanagon@GERRY.VANAGON.COM > >Subject: Understanding Amp Hours > >Date: Tue, 20 Jun 2006 08:43:35 -0700 > > > >The answer to another question here on the list raised this question. > >Given > >that we have the amp hour rating for a battery and also given > that we don't > >want to draw it down below about 10.5 volts, about 80%. Does > that amp hour > >rating assume draw down to the 80% level, or draw down to 'dead', > zero?>I've always assumed that if I have a 50 amp hour battery > that I can draw 1 > >amp for 50 hours before reaching the point that will require > charging, or > >will I only get 20% of that, 1 amp for 10 hours, before reaching > the point > >where I need to recharge? >


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