[RE-wrenches] Solar Boost Controller in Senegal

[Larry Crutcher, Starlight Solar]

If the SB50 is like other Solar Boost products, there is a zener diode  
on the PV input that will open if the voltage exceeds the Voc  
maximum.  The controller will not "burn up" or be fried but you will  
have to replace the diode. Why it has not happened yet on a cool  
morning is a mystery to me.

There is an adjustable MPPT pot for tweaking the MPP of the module(s)  
right next to the battery pos. terminal. Since the Voc is so high with  
the modules in series, you may want to adjust it. With the battery at  
a low SoC, tweak this pot slowly for highest current output. Make sure  
the MPPT LED stays lit while you adjust it.

"Is it a dangerous way to design a system?"  Not really but it was an  
ignorant person that did this. If it will get cooler as you say, there  
is a good chance the zener will open and the controller will stop  
functioning. The Vmp is too low to operate the panels in parallel due  
to your temperature. You may need to purchase a different controller  
that will handle the high Voc.

Kindest Regards,

Larry Crutcher
Starlight Solar
(928) 941-1660
Renewable Energy Products, Service and Installation

Mailing Address (NO SHIPPING):
11881 S Fortuna Rd.
#210
Yuma, AZ 85367

Shipping and retail store (NO MAIL):
2998 Shari Ave
Yuma, AZ 85365



On Jun 26, 2009, at 5:22 PM, Walt Ratterman wrote:

> 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   ▪   www.SunEPI.org
>
>
>
>
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