[RE-wrenches] Off-Grid Sizing Case

Windsun@wind-sun.com windsun at wind-sun.com
Thu Dec 3 10:18:52 PST 2009


Off-Grid Sizing CaseThe rate of charging is not the real problem in most undersized systems, it is the fact that the batteries seldom, if ever, get fully charged. Given the ratio of PV vs battery capacity, I would suspect that their batteries have been chronically undercharged for ages. We usually recommend around 1 watt of pv per AH for a 12 volt system, 2 watts for 24 volt etc.

A generator is not usually the answer, because it may have to run for hours to get that final 5-15% of charge into the batteries. Generators are good for equalizing, not so much for general charging.

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Northern Arizona Wind & Sun - Electricity From The Sun Since 1979
Solar Discussion Forum: http://www.wind-sun.com/ForumVB/
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  ----- Original Message ----- 
  From: Mark Frye 
  To: 'RE-wrenches' 
  Sent: Thursday, December 03, 2009 10:56 AM
  Subject: Re: [RE-wrenches] Off-Grid Sizing Case


  So being able to achieve C10 charging from the PV is not so important?

  Mark Frye 
  Berkeley Solar Electric Systems 
  303 Redbud Way 
  Nevada City,  CA 95959 
  (530) 401-8024 
  www.berkeleysolar.com  




------------------------------------------------------------------------------
  From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Windsun at wind-sun.com
  Sent: Thursday, December 03, 2009 9:51 AM
  To: RE-wrenches
  Subject: Re: [RE-wrenches] Off-Grid Sizing Case


  I would go with #1. The solar is obviously undersized for the battery bank he has. Another panel + MPPT should give him about 25-40% more, depending on temps etc.

  ..................................................................................................
  Northern Arizona Wind & Sun - Electricity From The Sun Since 1979
  Solar Discussion Forum: http://www.wind-sun.com/ForumVB/
  ..................................................................................................


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