# If controller is to small?



## budgetprepp-n (Apr 7, 2013)

HI
I'm going to put up two panels they are 245 watt ea. And I'm running 12 volts 
so,, 245 +245 = 490 watts -divided by 12 volts= 40.8 Amps 
I see that I should have a 40 amp charge controller but all I have right now is a 30 Amp
If the controller is to small will the controller be damaged or will it just be sort of
a bottle neck and hold back any power over 30 Amps?


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## PaulS (Mar 11, 2013)

The controller will never see the extra watts. The actual watts are lower than the "rated" watts of your panels. Your 490 watt panels will only produce about 90 - 95% of their rated power and your voltage is actually 12.5 to 13.5 volts so:
490 x 90% = 441 watts and 441 / 13 = 33.9 amps. The charge controller will only output 30 amps and the rest will be shunted or blocked depending on the internal circuitry. The panels will only produce that level of power as long as they are facing directly into the sun +/- 10 degrees. Unless you mount your panels on a tracking mount they will produce that maximum power for about three hours a day in the summer and less than that in the winter.

You should be good to go, but if you want to find out for sure, call the manufacturer of the charge controller. Their answer is worth more than my calculations and suppositions.


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## GTGallop (Nov 11, 2012)

In the process of putting solar on the house so I'm reading ALL of the solar posts on here. Commenting to follow this one and see where it goes.


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## budgetprepp-n (Apr 7, 2013)

GTGallop said:


> In the process of putting solar on the house so I'm reading ALL of the solar posts on here. Commenting to follow this one and see where it goes.


Well I'm going to find out. I have 4 245 watt panels I'm going to stick on my roof soon as I figure how to make them adjustable 
for the seasons without breaking the bank

I'm only going to have 3 angle adjustments Summer, Winter , Spring and Fall.


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