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
wratter...@sunepi.org ▪ www.SunEPI.org
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