[RE-wrenches] PV excellent battery charger

[Darryl Thayer]

I have never seen the exam but I have been told several of the questions are nonsense.   Just like the study guide, and  from what I hear  there are  questions  of similar  nature on the installers exam.  Something is wrong with the test generation.  
Darryl

--- On Sat, 3/27/10, Warren Lauzon <windsun at wind-sun.com> wrote:

From: Warren Lauzon <windsun at wind-sun.com>
Subject: Re: [RE-wrenches] PV excellent battery charger
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Date: Saturday, March 27, 2010, 10:55 AM



 
 

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

  ----- 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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