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What would be the best config for 2 X 265W and 2 X 270W (12V each)? 270's in series in parallel with the 265's in series OR 2 X 265+270 (S) in (P)? I know mixing power make you loose efficiency, but I own the 2 265 and someone offered me to give me the 270's. I'm using a 24V system (MPPT). What gauge of cable should I use for 80' of cable with this config? Thanks!
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Check the Vmp and Imp of those panels. If they are within 5% of each other then you should be able to treat them as the same. How you wire them will be determined by the CC max input rating which is where you have to consider the Voc ratings. To high and your CC may burn up.
The cable size is determine by the amount of amps they are carrying along with a voltage drop calculation. Until you provide more info on the panel specs and orientation then it would be difficult in providing a cable size for your system. -
If the panels are as good a match as the ratings indicate, the arrangement
will not be critical.
You have 270W 12V panels, so with an MPPT of around 15V the current
would be 18A, right? At 80 feet and a round trip loop length of near 180 ft,
your most efficient arrangement is 4 panels in series. But that might present
100V to your controller, check actual rating and temp range to avoid blowing
it. With 60V from series panels at 18A , 2% loss would be 1.2V.
Loop resistance needs to be limited to E/I or 1.2/18 equals 0.067 ohms, or
0.00037 ohms per foot. That puts you around 6 gauge. Using a series-
parallel panel arrangement gives twice the current at half the voltage, you
would need 4 times as much copper to get the same efficiency. Bruce RoeComment
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