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
Yes that was a plan I proposed based on last year's results for those who have two 12s instead of one big 24. Series MPPT for the cold half, parallel PWM for the warm half of the year. It is easy enough to do a comparison if you have both an MPPT and a PWM controller for when to swap over.
My problem is that my MPPT controller is borderline Voc limited for two 12s in series at 42-45 Voc limit, so I would rather have a different controller with an higher Voc limit if adopting that scheme.
One testing issue is that usually you run loads to keep battery voltage from rising during the comparison tests. Also the PWM controllers do better with battery voltage a bit lower in the mid 12s to mid 13s per IV curves, while the MPPT controller does better with low battery voltage too.
But with a 24v bank, you don't have any loads you can run for that job unless you happen to have a 24v inverter. So for today's tests I had to work at getting the bank down in voltage ahead of time while it was still 12v. After that when disconnected, the trick is to not leave the current flowing very long from one test to the next, so the battery voltage doesn't get higher between tests. It is all a bit frantic, but you can manage if you plan it out ahead of time how you will proceed.
My problem is that my MPPT controller is borderline Voc limited for two 12s in series at 42-45 Voc limit, so I would rather have a different controller with an higher Voc limit if adopting that scheme.
One testing issue is that usually you run loads to keep battery voltage from rising during the comparison tests. Also the PWM controllers do better with battery voltage a bit lower in the mid 12s to mid 13s per IV curves, while the MPPT controller does better with low battery voltage too.
But with a 24v bank, you don't have any loads you can run for that job unless you happen to have a 24v inverter. So for today's tests I had to work at getting the bank down in voltage ahead of time while it was still 12v. After that when disconnected, the trick is to not leave the current flowing very long from one test to the next, so the battery voltage doesn't get higher between tests. It is all a bit frantic, but you can manage if you plan it out ahead of time how you will proceed.
