30A or 40A controller?
I’m going to mount 2 160w panels rated at 9.5 isc amps to feed 2 6v batteries…260ah. If I were to mount a 3rd panel I’m still under 30amps so a 30 amp controller should work fine….or should it. I’ve ...
Forum Discussion
pianotuna wrote:
Hi,
It will work but it may be more economical to use a Pwm controller.
Blue Sky does not make a controller that is 40 amps. Was that a typo?
I have the BS 3024 di. The 30 is the amps, the 24 is the maximum battery bank voltage.
ISTR those Blue Sky controllers have a lower recommended amp limit than their "name" amps implies.
With a PWM controller you have to "allow" for the panel doing more than its rated amps at times. 1.25 rated Isc = controller amps (then do 1.25 of that for the fuse size and wire gauge calculation)
With an MPPT controller that clips the amps to its full rating, you can go to that without the 1.25 margin on the controller. You still need 1.25 on the fuse AFAIK.
NEC wants circuit breakers etc to operate continuously at no more than 80% of their ratings. This does not necessarily apply to solar controllers. They may already have that margin built in, like the Morningstar ones that are ok with clipping to their max amp ratings.
It is not all so straight-forward out there as it should be, it seems! :(
