12v MPPT and 24v MPPT vs 24v PWM Test
Got a chance to try out comparing amps to the battery using MPPT vs PWM on a 24v battery bank and comparing those with the usual MPPT on 12v with my 230w panel. The bank is four 6s, so it was easy ...
Forum Discussion
EDIT saw the above-- note the current on the panel to controller path is the same either way. Panel is rated at 8.3 amps Isc and the PWM will do that with high sun etc. The MPPT runs at Imp of about 7.7 amps, so there is no difference in line loss due to current on that path.
Meanwhile the controller to battery path is the same too at battery voltage so same line loss if any. I can't measure any loss there on mine.
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There is nothing wrong with the MPPT controller. Get over it :( I did the efficiency thing and there it is, same as a Morningstar's.
Amps to the battery are lost with MPPT because of panel heating killing its watts. PWM does not lose amps from panel heating and it doesn't use watts anyway, just amps. At some point you get more amps with the PWM just from that.
You have to compare 24-24v or 12-12s to be fair, because there is a loss going from 24-12 and the PWM can't do 24-12.
We will see this summer how the numbers come out compared with last summer, now I know I can run my 230w panel with the Solar30 as long as the battery bank is 24v too.
Last year in the Spring it was MPPT 15.5 amps (like today) vs 14.5 amps with PWM using 12-12 for the same 230w. By mid-Summer, hot panel, MPPT was 13.5 amps while PWM would still be 14.5. ( I know all the bumph says this is impossible--so measure your own and see what you get! )
My aim here is to see if I can replace that lousy 13.5 amps from the MPPT with more amps using the Solar30 and 24-24. Since the panel rated amps is 8.3, I hope to see 8.3 on the 24 from the PWM which would be like 16.6 amps instead of that 13.5. Based on today's test, it looks possible :)
16.6 is higher than the 14.5 because the ratio of Isc to wattage is higher with the 230w panel than it was with the 130w panel at 8.2.
Using the 130w's ratio to get expected amps from 230w you would see 230/130 x 8.2 = 14.5 amps
BUT the 230w rated Isc is 8.3 which would be 16.6 as a "12v"
So it seems you could get more amps with a single 240w panel in PWM with 24 batts, than with two 120s in series for 24 and the same PWM!
Somebody with a pair of 12v panels can test that out and report back here :)
Meanwhile the controller to battery path is the same too at battery voltage so same line loss if any. I can't measure any loss there on mine.
-----------
There is nothing wrong with the MPPT controller. Get over it :( I did the efficiency thing and there it is, same as a Morningstar's.
Amps to the battery are lost with MPPT because of panel heating killing its watts. PWM does not lose amps from panel heating and it doesn't use watts anyway, just amps. At some point you get more amps with the PWM just from that.
You have to compare 24-24v or 12-12s to be fair, because there is a loss going from 24-12 and the PWM can't do 24-12.
We will see this summer how the numbers come out compared with last summer, now I know I can run my 230w panel with the Solar30 as long as the battery bank is 24v too.
Last year in the Spring it was MPPT 15.5 amps (like today) vs 14.5 amps with PWM using 12-12 for the same 230w. By mid-Summer, hot panel, MPPT was 13.5 amps while PWM would still be 14.5. ( I know all the bumph says this is impossible--so measure your own and see what you get! )
My aim here is to see if I can replace that lousy 13.5 amps from the MPPT with more amps using the Solar30 and 24-24. Since the panel rated amps is 8.3, I hope to see 8.3 on the 24 from the PWM which would be like 16.6 amps instead of that 13.5. Based on today's test, it looks possible :)
16.6 is higher than the 14.5 because the ratio of Isc to wattage is higher with the 230w panel than it was with the 130w panel at 8.2.
Using the 130w's ratio to get expected amps from 230w you would see 230/130 x 8.2 = 14.5 amps
BUT the 230w rated Isc is 8.3 which would be 16.6 as a "12v"
So it seems you could get more amps with a single 240w panel in PWM with 24 batts, than with two 120s in series for 24 and the same PWM!
Somebody with a pair of 12v panels can test that out and report back here :)
