outback solar mppt controller
anyone had any experience with the outback mppt controllers? I see solar blvd has a 10A for $99 and a 20A for $149. the 20 A would be a nice update from the morningstar 15A at a reasonable price...
Forum Discussion
KD4UPL wrote:Almot wrote:
Educate me, people - why would anyone want a 10A MPPT?
So you can get the maximum output of your solar panel. A 120 watt panel normally has an Imp of about 7 amps. If you use a PWM controller and the panel sees battery voltage of about 14 volts the most power you'll get is 98 watts. You give up the other 22 watts unless you use an MPPT controller.
Much confusion here. A 120w panel (mine did) has a Isc of 7.6 amps, which I got with the panel aimed at a high sun using PWM with batt voltage around 13.5. it was a little less in amps when batt v got higher, then fell off the knee cliff at 15v.
so with an MPPT controller on the same aimed panel, you would see the panel reduced (by heating) in voltage and so watts by about 8.6% to 110w. Now you have at best, 1% wiring loss between panel and controller =1w so now you have controller input =109w
Controller efficiency is approx. 95% so output watts is say 103.5w NOW you divide that by battery voltage at the time to get your charging amps.
At 13 v, it is 109/13 = 8.4 (more than the 7.6 Isc that PWM gives you)
At 14 v, it is 109/14 = 7.8 (near the same as PWM gives)
But let's say the Rver has such limited roof space he can only fit a 120w panel no bigger. He can get more out of it by going MPPT while the battery voltage is still low. He can also get more out of it in the shoulder hours as seen in Salvo's diagram (where his 130w panel amps are near 8.2 max, so a 10a controller would be ok.
