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
12thgenusa wrote:jrnymn7 wrote:BFL13 wrote:jrnymn7 wrote:
Even with 12v to 12v mppt being more efficient, wouldn't 24v to 12v mppt yield more in the way of Amps to the battery? And would it depend on whether the 24v is from an actual 24v panel, or two 12's in series?
My answer to that first question is right there in the OP assuming 24-24 is like 12-12
The second question would depend on any wiring losses from the parallel links which you don't have with a single panel? I don't know any reason why they should be different otherwise. (Except in partial shade maybe)
What I find most interesting is that higher Isc proportion in the single 230w than in the 130w, which ought to make the single 230w with PWM (so it would have to be on a 24v battery) do more amps than two 115w panels in series with PWM on a 24v battery.
Ah yes, that's what you made reference to, earlier. So let's compare:
24v / 250w panel, Isc 8.39a
12v / 125w panel, Isc 7.38a (7.97 x .9259)
8.39/7.38 = ~ 13.5% extra!
You're forgetting that you don't have a 12 volt or 24 volt panel. Nominal 12 volt panels might actually be from 17 to low 20s and nominal 24 volt panels might be from 27 to low 40s.
Nothing can be derived from your calculation.
PWM CHARGE CONTROLLERS can be used with either 12v or 24v panels, provided it's 12v panel to 12v battery, or 24v panel to 24v battery.
PWM controllers pass thru Isc.
Using the panel specs of two particular panels found on 2solar.com...
The 24v 250w panel has an Isc of 8.39a.
Two of the 12v 135w panels, adjusted down to 125w, in series, have an Isc of 7.38a.
8.39/7.38 = 1.1369... that's 113.7% Therefore, the 24v panel would deliver 13.7% more current to the pwm, and 24v battery.
