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
pnichols wrote:BFL13 wrote:
Because "MPPT" controllers have buck converters in them and "PWM" controllers do not. Never mind the tracking trick to get MPP, the thing is you need the buck converter to go 24-12, or 48-12, whatever.
Given the typical 12 volt RV battery bank, doesn't what you say lead to the logical conclusion that if one wants the best solar energy capture efficiency possible, then they should go with 24 volt (or higher) panels feeding an MPPT controller? There should also be some small plus that results from a little bit less voltage drop in panel to controller wiring with 24 volt (or higher) panels over 12 volt panels.
However, wouldn't a single 24 volt 200W panel's output fall off a lot faster from partial shading than the total output would fall off from two paralleled 100 watt 12 volt panels in the same partial shading?
It is only true that you get more with MPPT in certain circumstances. Based on my own results, that puts PWM ahead in the summer when panels get hot. The "usual blurbs" say this will never happen, but only that PWM will almost do as well as MPPT when it gets hot. I have not found any explanation for the difference I see in real life (except Salvo saying my controller is garbage and I can't measure anything worth a hoot)
You can cherry-pick circumstances to suit any argument position you want for when MPPT does better. Mine does better at panel 44C but not at 50C when PWM does better.
Most MPPT goes with stick houses at 48v, so what we do in RVs is peanuts to the industry. They use 48v inverters with their 48v panels. I don't know what they do with battery voltage. 48v would be most efficient with 48v panels.
