600W Solar - Getting 420W Max
I have 5 120W Solar panels flat mounted. I am in Mission TX at a FHU park for the winter. It is giving me a good place to test my system out. Back in the NE there are to many trees. I have seen a max ...
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The 60 cell "amps advantage" didn't happen in real life though.
I expected to get panel Isc by using PWM but instead of 9 amps I got 8 amps with both the MPPT and PWM controllers in 24-24. Amps would not go higher at full insolation. I suppose that has to do with the 60 vs 72 cell business, but it didn't affect the comparison.
If I had 72 cells, the voltage would be higher but the amps lower on the same 255w. So I should get the full Isc, but that Isc would be less, so I figure it is a wash. A watt is a watt.
(The 60 vs 72 did show up in terms of "overhead" when I could not get the 24v batts higher than 30v (like 15v on 12v) but that is not an MPPT vs PWM thing--neither could get the batts higher.)
EDIT--example 72 cell 310w vs 60 cell 255w(mine) -both CanSolar
Vmp- 36.4/30.2
Imp- 8.52/8.43
Voc- 44.9/37.4
Isc- 9.08/9.0
So compare getting Isc with 310w worth of 36 cell 12v panels vs MPPT with that 72cell 310w panel.
PWM- 310/130 x 8.2 = 19.55 amps (like 9.8 at 24v)
MPPT -310w minus 8.6% for heat (20C above 25C-- 45C) = 310-26.7 = 283.3w minus 2% line loss to controller 5.7w = 277.6w input minus 5% controller loss 13.9w = 263.7w output. ---at 26 battV, 263.7/26 = 10.14 amps
So it is 10.1 vs 9.8 using 2% line loss and 5% controller loss for the MPPT (does not affect the PWM) If I picked 3% line loss and 6% controller loss it would be 283.3-8.5 = 274.8 - 16.5 = 258w/26 = 9.9a vs 9.8 amps.
So now what if it were warmer out like when it was 25C and panel was 51C? Now panel heat loss is 51-25 = 26 x 0.43 = 11.2% (34.7w) instead of that 8.6%.
So now 310-34.7= 275.3 minus line loss (use 2% again, why not?) 5.5w = 269.8 minus controller loss (5% again, why not?) 13.5w = 256.3/26 = 9.85 amps vs 9.55 amps--Drat! Should have used 3% for line loss :)
I expected to get panel Isc by using PWM but instead of 9 amps I got 8 amps with both the MPPT and PWM controllers in 24-24. Amps would not go higher at full insolation. I suppose that has to do with the 60 vs 72 cell business, but it didn't affect the comparison.
If I had 72 cells, the voltage would be higher but the amps lower on the same 255w. So I should get the full Isc, but that Isc would be less, so I figure it is a wash. A watt is a watt.
(The 60 vs 72 did show up in terms of "overhead" when I could not get the 24v batts higher than 30v (like 15v on 12v) but that is not an MPPT vs PWM thing--neither could get the batts higher.)
EDIT--example 72 cell 310w vs 60 cell 255w(mine) -both CanSolar
Vmp- 36.4/30.2
Imp- 8.52/8.43
Voc- 44.9/37.4
Isc- 9.08/9.0
So compare getting Isc with 310w worth of 36 cell 12v panels vs MPPT with that 72cell 310w panel.
PWM- 310/130 x 8.2 = 19.55 amps (like 9.8 at 24v)
MPPT -310w minus 8.6% for heat (20C above 25C-- 45C) = 310-26.7 = 283.3w minus 2% line loss to controller 5.7w = 277.6w input minus 5% controller loss 13.9w = 263.7w output. ---at 26 battV, 263.7/26 = 10.14 amps
So it is 10.1 vs 9.8 using 2% line loss and 5% controller loss for the MPPT (does not affect the PWM) If I picked 3% line loss and 6% controller loss it would be 283.3-8.5 = 274.8 - 16.5 = 258w/26 = 9.9a vs 9.8 amps.
So now what if it were warmer out like when it was 25C and panel was 51C? Now panel heat loss is 51-25 = 26 x 0.43 = 11.2% (34.7w) instead of that 8.6%.
So now 310-34.7= 275.3 minus line loss (use 2% again, why not?) 5.5w = 269.8 minus controller loss (5% again, why not?) 13.5w = 256.3/26 = 9.85 amps vs 9.55 amps--Drat! Should have used 3% for line loss :)
