...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/
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----- Original Message -----
*From:* Walt Ratterman <mailto:wratter...@sunenergypower.com>
*To:* 'RE-wrenches' <mailto:re-wrenches@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...
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