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
jrnymn7 wrote:
Jim,
"Battery bank "resting" voltage before the tests was 12.4 volts, low enough to accept all the amps."
At such a low charge rate, the mppt controller should have been operating in mppt mode, no?
The lower the voltage of the bank, the more of the panels output you lose in PWM mode. You take a double wammy early on with low light and low voltage, just when you need the power the most to bring up the voltage of the bank. That is the theory anyways. I like seeing real world test results that put those theories to task.
BFL
The working voltage of 230w poly is 4v above a full 24v bank. There isn't much of anything for ANY MPPT controller to work with. Pretty much like running 12v panels in parallel into a MPPT controller, any improvement at all will be minimal. In this case two 12v in series may make a difference, maybe not. A 300w+ panel with a Voc of 45v may show a much larger difference between the controllers.
That's the thing about many "this is better" things. Better may not be massive or worth the cost unless you have too. Sometimes the better comes with unique situations in fine print. Meet all of the criteria and it is indeed better.
