[RE-wrenches] Solar Boost Controller in Senegal

[Darryl Thayer]

Perhaps the Zener and the high temperature has vorked together to protect the MOSFETs such that even though it is overvoltage, the Zener and low output current has not destroyed the circuit.  Just lucky perhaps
Darryl 

--- On Sat, 6/27/09, boB Gudgel <boB at midnitesolar.com> wrote:

> From: boB Gudgel <boB at midnitesolar.com>
> Subject: Re: [RE-wrenches] Solar Boost Controller in Senegal
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Date: Saturday, June 27, 2009, 2:35 AM
> Wind-sun.com wrote:
> > Yes, it is a poor design. though you may not have any
> problems there with the heat de-rating of the panels. If the
> panel temperature gets under about 40C you may blow out the
> input. As long as you have a load on the output of the
> contgroller, it will keep the voltage down, but if the
> output is disconnected the input could go up to full
> voltage.
> 
> Remember that this controller opens up every so often, (8
> seconds or so?) to check Voc and adjust the MPP-V based on
> that measurement.
> 
> boB
> 
> 
> 
> 
> >  Who designed such a system?
> > 
> ..................................................................................................
> > Northern Arizona Wind & Sun - Electricity From The
> Sun Since 1979
> > Online Store: http://store.solar-electric.com/
> > Solar Discussion Forum: http://www.wind-sun.com/ForumVB/
> >
> ..................................................................................................
> > 
> >     ----- Original Message -----
> >     *From:* Walt Ratterman
> <mailto:wratterman at sunenergypower.com>
> >     *To:* 'RE-wrenches'
> <mailto:re-wrenches at lists.re-wrenches.org>
> >     *Sent:* Friday, June 26, 2009
> 3:22 PM
> >     *Subject:* [RE-wrenches] Solar
> Boost Controller in Senegal
> > 
> >     Hello,
> > 
> >      
> >     I am in a very remote part of
> Senegal, (near the Guinea  and Mali
> >     borders…) and I have come
> across some prefabricated “plug and
> >     play” American made systems
> installed for educational institutions.
> > 
> >      
> >     The systems use two Sharp
> panels that are 220Watts, 33.6 Voc, 29.2
> >     Vmp, wired in series, using
> #10AWG home run wire from the panels
> >     back to the charge
> controller.
> > 
> >      
> >     Charge Controller is a Solar
> Boost 50. 
> >      
> >     Batteries are Dekka AGM –
> two strings of 250AH, 12V batteries. 
>    (four batteries total).
> > 
> >      
> >     My specific question is about
> the controller.  This is a 24V in /
> >     24V out charge controller with
> MPPT.  I have not used this before,
> >     so I am not familiar with the
> details of operation.
> > 
> >      
> >     The data sheet that I
> downloaded says that the maximum open
> >     circuit voltage is 57
> VDC.  But, this system is hitting the charge
> >     controller with two panels of
> 33.6 VDC wired in series for
> >     73.2VDC.  So, why is the
> controller not fried, or what am I seeing
> >     wrong here.  I suppose
> with the panel temperature being elevated
> >     maybe 35 degrees above 25
> degrees and a resulting 17.5% loss,
> >     coupled with some voltage
> drop, the system may actually be seeing
> >     less than the 57 volts. 
> >      
> >     But…..isnt this a dangerous
> way to design a system?  (it will get
> >     cooler here ….)
> > 
> >      
> >     Or am I missing something?
> > 
> >      
> >     What would be the appropriate
> application here….
> > 
> >      
> >     Sorry, I cant do a lot of
> internet research from here – limited
> >     download capability on the
> satellite….
> > 
> >      
> >     Thanks!!
> > 
> >      
> >     Walt
> > 
> >      
> >     *Walt Ratterman*
> > 
> >     *SunEnergy Power
> International***
> > 
> >     * *
> > 
> >     11 Laurel Lane South 
>    Washougal, WA   98671
> > 
> > 
>    (360)-837-3680   ▪   fax
> (360)-837-1315   ▪   Skype 
> Walt-Mobile
> > 
> >     wratterman at SunEPI.org
> <mailto:wratterman at SunEPI.org>   ▪ 
>     www.SunEPI.org <http://www.sunepi.org/>
> > 
> >      
> >      
> > 
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