Self Discharge Rates [RE-wrenches]

[Richard Perez, Home Power magazine]

<x-flowed>Hello Wrenches

Deep cycle (high antimony) flooded cells self discharge about 4% of 
their capacity weekly. This rate is highly temperature 
dependent--higher temps mean more self-discharge. Since the average 
discharge of a properly designed PV system is less than 12% nightly, 
this self discharge doesn't need to be factored into the system's 
design. When high antimony batteries age (about 8 to 15 years 
depending on energy maintenance), the self-discharge rate can reach 
up to 25% of their capacity weekly.

I concur with Travis's experience on the Concorde AGMs. Very low 
self-discharge and very tough. We have eight of them here in various 
systems and they are the only sealed battery I've ever thought 
effective.

Richard Perez

At 14:39 -0700 8/24/00, Travis Creswell, Ozark Solar wrote:
>Concorde claims that their AGM product self-discharges at less than 1% per
>month.   I recently hooked up set of 12 volt 255 amphour that had been
>stored for over a year with no charging and they are doing fine.  I did have
>to take them through a few easy cycles to get their voltages evened up but
>they seem to be doing great now.  I'm not recommending this but I was very
>happy that they survived.  I think the key was they were stored in a
>warehouse all winter which never got to far from 60 f.  Based on how many
>amp hours I had to put back in this set I wouldn't argue with that 1% number
>too much.
>
>What about flooded batteries?  Does anyone compensate for their high self
>discharge when sizing systems?  Ed Mohoney from Concorde claims that they
>self discharge at 25% per month especially as they get older?  Anyone agree
>with that?  What is a reasonable number I'm pretty sure NiCads are even
>worse.  I like the Concordes and have found them to be really tough but they
>are lot more money than L-16's.
>
>Travis Creswell

------------------------------------
Richard Pérez
Home Power
PO Box 520, Ashland, OR 97520  USA
Tele: 530-475-3179
FAX: 530-475-0836
Subscriptions: 800-707-6585
mailto:richard.perez at homepower.com
Web: http://www.homepower.com

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