Calling on Solar Techies
I have been thinking of going solar for some time and decided to pull the plug. My wants are a 400 to 500 watt system. I have four 12 volt batteries with 340ah. I am not planning on changing b...
Forum Discussion
MPPT ads always talk about how PWM "wastes" power, but neglect to say that panel heating kills about 10% of the rated power before it even gets to the controller input. So you could call that "wasted" power too.
PWM does not care about power, it uses available amps which are the same as the Isc at the time.
It can happen, as I have posted with my results while camping with both MPPT and PWM, that by the time you reach the MPPT output watts (the power) and divide by battery voltage to get your amps to the battery, the PWM amps to the battery (same as Isc--which goes up with panel heating) can be close to being the same.
You get the most in percentage with MPPT over PWM in the early morning when battery voltage is low, the sun is low, and amps are low. Now you could have 2 amps with PWM and 4 amps with MPPT. Wow, that is 100% more! Wheee. (Never mind that is only 2 more AH for the next hour)
Tell "Sales" to use that in the ad! Don't mention the figures at high noon when the percentage gain with a near full battery is hardly any. That's no fun.
There is no choice but MPPT when you use 24v panels, which are a better price per watt than 12s, so it doesn't matter then. You only have the choice of PWM if you buy those more expensive 12v panels. (or have a 24v battery bank too and do 24-24)
Lots of factors and scenarios. IMO the OP is on the right track for his situation, and can adjust as required in future.
PWM does not care about power, it uses available amps which are the same as the Isc at the time.
It can happen, as I have posted with my results while camping with both MPPT and PWM, that by the time you reach the MPPT output watts (the power) and divide by battery voltage to get your amps to the battery, the PWM amps to the battery (same as Isc--which goes up with panel heating) can be close to being the same.
You get the most in percentage with MPPT over PWM in the early morning when battery voltage is low, the sun is low, and amps are low. Now you could have 2 amps with PWM and 4 amps with MPPT. Wow, that is 100% more! Wheee. (Never mind that is only 2 more AH for the next hour)
Tell "Sales" to use that in the ad! Don't mention the figures at high noon when the percentage gain with a near full battery is hardly any. That's no fun.
There is no choice but MPPT when you use 24v panels, which are a better price per watt than 12s, so it doesn't matter then. You only have the choice of PWM if you buy those more expensive 12v panels. (or have a 24v battery bank too and do 24-24)
Lots of factors and scenarios. IMO the OP is on the right track for his situation, and can adjust as required in future.
