battery cycle life [RE-wrenches]

[Jeff Clearwater]

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Hey Victor,

Very True.  AND too small and they get hammered by deep cycling and 
sulfation and you waste energy to mismatch of source and load.

It depends on so many factors.  On-grid vs off-grid is a world of 
difference.  Size and frequency of loads. Gen Size, PV/Wind vs 
inverter size and total load,   But in general I see more problems 
with too small of a pack off-grid than I do with too  large  one.

Theres no quick and easy rule of thumb here.  You have to run the 
numbers and look at your assumptions carefully - how many days 
backup?  of what loads?  inputs vs outputs?  etc. etc.  Anybody 
installing off-grid packs that have not familiarized themselves with 
Peukert's equation, sulfation issues, DOD vs. Lifetime, % full vs 
load/charge curves is probably doing their customers and themselves a 
disservice.  Read Battery Book One by Curtis instruments.  And sell 
battery maintenance service contracts and keep care of them for them!

Peace,

jc


>Hi Jeff,
>
>  You said "80% DOD ensures that
>you are going to spend alot of your time with less
>than 50% charge in
>your batteries due to slow charging from the PV array"
>
>  A smaller battery means charging at a higher C/x
>rate. Bergey Windpower recommends a battery capacity
>of six times your non dispachable charge current, and
>I'm leaning towards this. I'm only involved with wind
>and wind PV hybreds and C/6 does sound too stiff for a
>PV only system, however it has it"s virtues. Mainly it
>ensures that the batteries get really full during a
>wind event instead of almost full as is the case with
>oversized battery banks. It also puts the owner in
>touch with the fact that energy out cannot be more
>than energy in over long periods of time. Also you
>have probibly seen systems where the battery is so
>large compared to the energy source that self
>discharge becomes a significant load to overcome to
>get the battery to 100%.
>   Ever heard a client answer "well I ran the generator
>for FIVE hrs" when you asked when was your last
>equilizing charge? With a smaller battery 5 hrs means
>something
>
>Make the wind fun!
>Victor Creazzi
>Aerofire Windpower
>

-- 
~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design Associates
Sustainable Energy & Water Solutions for Home & Village
http://www.villagepower.com
gosolar at villagepower.com

530-470-9166
877-SOLARVillage
877-765-2784
425 Nimrod St.
Nevada City, CA 95959
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