mppt vs pwm

Salvo wrote:
Your logic is nonsense. Not worth bring up. No one in their right mind will use a 72 cell panel in a 12V pwm system.

The same rules apply when comparing 400W 36 cell panels using pwm and 400W 72 cell panels using mppt. The difference in gain will be on average only 5%.

Higher voltage arrays are virtually all that are being installed anymore -- everyone's doing it. It's getting difficult to even find good 12v panels, at least at a price that's anywhere near the $/watt that you'd pay for higher voltage ones. Gains are MUCH greater than 5% when converting a higher voltage array to a lower voltage bank using an MPPT, versus what you would get with a direct connection or PWM controller. The latter is not even a consideration because the losses would be off the charts.

Take a panel with these specs and charge a 12.6v battery with it:
Pmax: 185 Watts @ STC
Vmpp: 36.0 Volts
Impp: 5.15 Amps
Voc: 44.8 Volts
Isc: 5.50 Amps

With PWM (if you don't smoke your controller in the process) you'll have about 69 watts (12.6 * 5.5). With MPPT you'll have 185 watts (36 * 5.15). This is ignoring the effect temperature has, of course. The listed tempco of Pmax is -0.905watt/degC. So assume a 40degC temp rise over STC and you'll lose about 36 watts, which still leaves you with 149 watts. That's 215% of what you'd be getting with PWM. Where are you getting 5% from?