Need your $0.02 on charge controllers
Currently I have a 50 watt panel with a Sun Saver 10A charge controller. Based on my needs/wants/calculations/funds/roof space etc, I want to add another (2) 100-150 watt panels. I am going to do t...
Forum Discussion
portscanner wrote:pianotuna wrote:
Hi,
How many watts will the completed system have? Do you want to squeeze ever watt out of the panels?
350 watts and yes!
Ignore all those other guys who want to spend your money for you. :)
MPPT controllers clip the amps to their amps ratings so the 20
% margin rule does not apply, but with PWM controllers that let the amps through past their ratings, but heat up when they do, the advice is to get a controller with a rating 20% higher than your "expected max amps"
How high is that? With PWM and "12v" panels that is Isc amps (Imp has no meaning with PWM) so 350w should get you 350/130 x 8.2 = 22a. and you need 20% more, so you need 22 + 4.4 = a 26.4a controller. So you need a 30a PWM controller.
With MPPT getting you 10% more, that would be 22 + 2.2 = 24.2a (plus the clipped amount) so you need a 25a MPPT. ( ISTY there is a BlueSky MPPT 25 amper. No idea if it is any good)
So what to do? It is all about money. A 30a PWM controller is under $100, while a 30a MPPT is over $300. Either way you get the same amps!
So unless you want to toss $200 down the drain, get a 30a PWM. Or if you feel the unstoppable need to program your controller on your laptop (WHY?) get the fancy one for more money. You are over 21, and you can choose. :)
