Last year I was stuck by having two 12v 100w panels and a 20a controller I happened to have and also had a 130w 12v panel. I had a second 20a controller for the 130w panel so all was good. What I actually needed was a single 30a controller to run all three panels.
If I wanted to go MPPT with those three panels, that would mean I still needed a 30a controller, but now with those three in series, I would need a Voc limit above 66 Voc for the three at 22 each.
It turns out this is not so easy to find where you want a Voc limit of 100v or so and at least 30a to go 24v MPPT.
As it happened, I sold the two 100w panels and got a 230w panel instead but this is 24v and the 130 is 12v, so I can't use just one controller. My bad. So I now have an MPPT controller that can do that 230w panel (but no more with its 42Voc limit) and a second PWM controller for the 130w panel.
However, I did end up getting a new PWM 30a controller for the 130w panel that would have been perfect last year to run my three 12v panels. It cost $34.
It is still madness to buy these over-fancy MPPT controllers for hundreds of dollars where you don't get many more AH per day than with the PWM $34 job. There is some cost savings in some market places where you get a lower cost per watt on the panel by choosing the 24v panels instead of the 12v panels and putting those in series to get the 24v.
But then you need an MPPT controller and those feeling patriotic pay hundreds of dollars extra for their patriotism, when they refuse to buy Chinese. What is badly needed is a "patriotic" MPPT controller that does not cost an arm and a leg.
.
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.
