mppt or pwm An opinion from Victron
Hi all, Victron, which makes high quality equipment, has charge controllers. At the end of an overview they give their description of the differences between PWM and MPPT. They do not support it wi...
Forum Discussion
JiminDenver wrote:
I've never had my Schott poly 230w peak out at 13.5a no matter what the temperature. Maybe 14.5a once but generally it's a solid 15-16a depending on here or at altitude. The difference in peak on my 245w twins was 16.5a on a hot day vs 17.1a on a cold clear morning, both tracking. The Canadian solar 220w mono is a very solid 12a here unless you put it in freezing temps, then you get a extra 3/4a. I don't see a huge drop with heat (80-90s), just a bit of a rise from cold. (sub freezing)
I don't know the battery voltages that "go with" those amps. We know that at lower battery voltages you get more amps from MPPT.
Taking 13.5v Vbatt , same as in my examples, then the controller outputs are:
A. 230w does 16.0 x 13.5 = 216w, 6% less
B. 245w does 17.1 x 13.5 = 231w, 6% less
C. 220w does 12.0 x 13.5 = 162w, 26% less
In any case, what I was trying to say earlier, is
- that people keep pointing out that the watts at the battery with PWM is less than panel rating so a bunch of watts gets "wasted" and having MPPT will rescue and use those wasted watts.
- but here we see that watts to the battery are also less than panel rating with MPPT so why don't those missing watts get called "wasted" too? Looks like "spin" perhaps?
Controller efficiency is involved somewhat but I don't know how much. MPPT controllers have the buck converter while 12v PWMs do not is one thing.
And for Salvo, a better reply is as above, where the so-called PWM "waste" is wrt panel rated watts, not the actual watts at controller input, so using panel rated watts in the MPPT case is fair comparison.
The lack of temperature difference in amps to battery at altitude Jim reports compared with what I see at sea level might have to do with air mass too, but I don't know. There might be a different ratio of ambient to panel temp up there with a lower air mass so the panel gets to the same sort of temp regardless of ambient? Don't know.
I have been puzzled by the lack of proportion in my temps where 16C-44C ( almost three times) is different from 25C-51C. (double) although each is about 27C above ambient.
Seems to be a lot to this business. Good thing all we have to do is put out the solar panel and enjoy. :)
