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Homemade solar panel dropping volts and amps | 7 comments (7 topical, editorial)

Re: Homemade solar panel dropping volts and amps (3.00 / 0) (#3)
by DanG on Sun Sep 7th, 2008 at 07:51:29 AM MST
(User Info)

Yes it sounds like you have a hairline crack, cold solder joint or the tabbing lifting somewhere that chokes current flow when the cells expand in the heat.
----
Your 'about 0.8V for every 10°C rise' may be exaggerated; that got me playing with numbers from my 'wish-list' panels spec sheet to show an example...

Allowed temp range: -40 to +90° C

Cell temperature coefficients (Voc at 25°C 63.2 & Isc 6.5)

Power TK (Pp) - 0.47 % / °C
Open-circuit voltage TK (Voc) - 0.38 % / °C
Short-circuit current TK (Isc) + 0.10 % / °C

Power drop w/ 10°C rise would be -4.7%
Voc drop w/ 10°C rise would be -3.8%
Isc current will rise 1% with 10°C temperature rise!

So my 'wish-list' panels at 90°C would drop from 63.2VOC to 38.5V and at -40°C peak power is increased 30.5%!

Homemade solar panel dropping volts and amps | 7 comments (7 topical, 0 editorial)

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