[RE-wrenches] PV excellent battery charger

[Warren Lauzon]

To be honest, I don't think the question makes any sense. There are several "right" answers, but no good ones. I hope that is not the extent of the battery questions on that exam.

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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: Drake Chamberlin 
  To: RE-wrenches 
  Sent: Saturday, March 27, 2010 9:28 AM
  Subject: Re: [RE-wrenches] PV excellent battery charger


  Hi Dave, 

  At 10:44 AM 3/26/2010, you wrote:

    Is the answer here (at least the one that NABCEP intends) just that the VMP of a "12V module" is higher than the voltage of a 12V battery? With the higher voltage it will charge the battery with its corresponding current based on the I-V curve. The objective reads "Explain why PV modules make excellent battery chargers based on their I-V characteristics


  This may be the answer they want.  The "Objectives" deals with the 5 key points on the IV curve, Vmp, Imp, Voc, Isc and Pmp.  >From a study of the curve, the obvious "excellent" load is one that takes power from Pmp, which direct battery charging doesn't do.  When I draw the curve, the Vmp of the module is above the resulting voltage on the curve.  

  What you say about the power loss not being released as heat in the batteries,  just not produced, makes sense to me.  I've never seen any real documentation about what happens to the power not gained in a non MPPT battery charging system. 

  We can definitely agree that "excellent battery charger" is an exaggeration. 

  Thanks,

  Drake 


  Drake Chamberlin
  Athens Electric
  OH License 44810
  CO License 3773
  NABCEP TM  Certified PV Installer 
  Office - 740-448-7328
  Mobile - 740-856-9648 



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