Serial vs Parallel Solar Panel Shading
I was asked if a post in another thread if this "Serial is actually better for shading (than parallel) if that is a concern for you." was a typo. It is not a typo but panel shading is not always under...
Forum Discussion
" PWM controller does not extract full power from any panel anyway"
Neither does MPPT. This is a bogus "hit" against PWM used by MPPT salesmen.
MPPT uses watts ( not Isc like PWM), which decline with panel voltage which declines with higher panel temperature which rises with sunlight on the panel (only time the panel is any good!) to the extent you immediately lose about 10% of panel rated power before you even get to controller intake watts. You also lose on voltage drop panel to controller and lose watts inside the controller before getting to controller output watts. Now you can divide output watts by battery voltage to get your actual amps to the battery.
Meanwhile the PWM controller just passes through the amps at Isc value
Result is that they come out about even for amps to the battery, but usually with a tiny amps advantage with the MPPT. I have even measured slightly better amps with PWM than with MPPT same set-up same conditions, just swap controllers. (This is supposed to be impossible according to that Dutch guy--I have news for him :) )
BTW I have found that parallel with MPPT works better than series with MPPT using my three 100w panels when there is any shading during the day. No diff with no shade) So playing the odds, IMO too--go with parallel on an RV.
Wiring only has to be done once, and it is just as much trouble to string thin wire as fat wire and the higher cost of fat wire is trivial in the big picture.
However, the cost of MPPT is not so bad anymore and 24v panels are half the cost of 12s, so it is not so easy to generalize about comparative costs for an RV solar set-up.
It may have more to do with roof space for the size of the panels that drives what you get. If 12s are the only thing that will fit, that's what you get. If you have the roof space it can still be cheaper to get one big panel and a Tracer or Eco-Worthy MPPT than go with more smaller 12v panels and a PWM. "It depends"
Neither does MPPT. This is a bogus "hit" against PWM used by MPPT salesmen.
MPPT uses watts ( not Isc like PWM), which decline with panel voltage which declines with higher panel temperature which rises with sunlight on the panel (only time the panel is any good!) to the extent you immediately lose about 10% of panel rated power before you even get to controller intake watts. You also lose on voltage drop panel to controller and lose watts inside the controller before getting to controller output watts. Now you can divide output watts by battery voltage to get your actual amps to the battery.
Meanwhile the PWM controller just passes through the amps at Isc value
Result is that they come out about even for amps to the battery, but usually with a tiny amps advantage with the MPPT. I have even measured slightly better amps with PWM than with MPPT same set-up same conditions, just swap controllers. (This is supposed to be impossible according to that Dutch guy--I have news for him :) )
BTW I have found that parallel with MPPT works better than series with MPPT using my three 100w panels when there is any shading during the day. No diff with no shade) So playing the odds, IMO too--go with parallel on an RV.
Wiring only has to be done once, and it is just as much trouble to string thin wire as fat wire and the higher cost of fat wire is trivial in the big picture.
However, the cost of MPPT is not so bad anymore and 24v panels are half the cost of 12s, so it is not so easy to generalize about comparative costs for an RV solar set-up.
It may have more to do with roof space for the size of the panels that drives what you get. If 12s are the only thing that will fit, that's what you get. If you have the roof space it can still be cheaper to get one big panel and a Tracer or Eco-Worthy MPPT than go with more smaller 12v panels and a PWM. "It depends"
