[RE-wrenches] NABCEP Exam was: PV excellent battery charger

Matt Lafferty gilligan06 at gmail.com
Mon Mar 29 10:50:41 PDT 2010


I wholeheartedly agree with and can confirm what Bob-O said.
 
-Matt Lafferty


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From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Bob-O
Schultze
Sent: Sunday, March 28, 2010 9:19 AM
To: RE-wrenches
Subject: [RE-wrenches] NABCEP Exam was: PV excellent battery charger


Folks, 
While none of us obviously has access to the wording of the specific
question itself, I can assure you that there are no "tricky" or non-sensical
questions on ANY of the NABCEP exams. Our Subject Matter Experts (SMEs) who
come up with the questions AND the answers aren't a bunch of nerds in a
university somewhere, they are us; working wrenches like ourselves. All the
questions and answered are submitted to a round table discussion of the SMEs
to be accepted, modified to be made clearer, or thrown out. At the same
time, they are reviewed by a professional testing expert for clarity,
readability, and correct usage of the language. Of the four answer choices,
there are almost always two which are dead wrong, one which could be arrived
at if you didn't follow all the steps of the question or didn't exactly know
the material, and the correct answer. If you think all that is easy to do,
try it sometime.
After the test is taken, the testing expert analyses the raw data and the
SMEs review any items which seem questionable. For example, if most of the
test takers INCLUDING those who did very well on the test otherwise missed a
certain question, they take a hard look at it to see if there is ambiguity
or if it can be interpreted differently from the way it was intended. It
does happen that in spite of all the work put into developing the question,
it is flawed in some way. When that happens, the question is discarded and
all the test takers in that round get credit for it.
As to putting together a study guide, that's even harder. Remember that it's
a "Guide", not a book like the NEC wherein lie all the answers to the
questions. The Entry Level test is not a snap by any means, but it is basic
in nature to our field and there are no questions on it that an installer
would have to face, IE, anything to do with the NEC. The Installer
Certification test is difficult, as it should be. Unless you know our trade
inside and out PLUS have done some study in the areas which you don't do at
all or very often (we all have those), you will have difficulty in achieving
a passing score. I know many good Wrenches who missed it at least the first
time. Some of those just say, "Screw it, I don't need this shit". Others
have challenged themselves to hit the books again and brush up on the areas
they found out (from taking the test the first time) where they were weak
and nailed it on the next round. Everyone I've ever talked to, including
myself, has said that they are a better craftsperson for having taken and
passed the test.
Bob-O


On Mar 27, 2010, at 8:02 PM, Darryl Thayer wrote:

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/
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----- Original Message ----- 
From: Drake  <x-msg://27/mc/compose?to=drake.chamberlin@redwoodalliance.org>
Chamberlin 
To: RE-wrenches <x-msg://27/mc/compose?to=re-wrenches@lists.re-wrenches.org>

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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