[RE-wrenches] Solar Boost Controller in Senegal

[Larry Crutcher, Starlight Solar]

...And the Voc is present every morning before the current is high  
enough to start the controller. That's when I would expect to have a  
problem. boB, I doubt that the Voc sample duration is long enough to  
cause a problem.

I know that Rick got back on this list a few months ago so if you  
(Rick) have any input to help Walt, we welcome your comments.

Larry Crutcher


On Jun 27, 2009, at 2:35 AM, boB Gudgel wrote:

> 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...
>