Solar Panel Disconnected from SUN
I am planning installing 4X140W panels(parallel)flat mounted going to 15A breakers(so they can be switched off if needed) to the charge. The panel have ISC of 7.50 each times 4 equal 30. The controlle...
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Mr Wiz said his Blue Sky 2000 (25 amp with 20 amp recommended max) clips any excess amps so it will not overheat and damage the controller.
It is the US NEC that wants the 20% margin for controller amps rating with controllers that do not clip their amps. Regular PWM controllers just pass through whatever amps they get and overheat if that is too many amps for them for too long a time.
So if your "expected amps" is 25 amps then NEC wants you to have a 30 amp controller for that 20% margin. Panels sometimes put out more than their rated amps, such as when they are cold or at high altitude, etc. The brief burst of high amps from edge of cloud effect doesn't matter AFAIK since that only lasts a few minutes at a time with those pretty white clouds going by the sun every so often.
So what is your "expected amps" anyway? If the Isc of your 140 is only 7.5a I suspect it is a mono panel with corresponding higher Voc too, since a 140w poly's Isc would be near 8.8a. If yours is poly maybe that 7.5 is Imp? (Imp does not apply to PWM)
But isn't the Blue Sky 3000 an MPPT controller? So now you have a complicated sort of "expected amps" depending on whatever watts you are getting and whatever the battery voltage is at the time, which is always changing.
So let's say your four 140s are mono with Isc of 7.5a as stated, and your expected amps will be at least as good as what PWM would get.
4 x 7.5s = 30. That's with panels aimed at high sun. Flat on roof will be less than that. It could be close with the sun overhead in summer in the south part of the USA mainland.
Your MPPT controller should clip the amps as required so no need to fuss with input if the controller is mounted properly with good ventilation cooling.
If I had four 140s I would make two pairs and get an eBay 20a PWM controller for each pair and parallel those two controllers on my battery bank. Save a bundle on controller costs and get approx the same amps.
It is the US NEC that wants the 20% margin for controller amps rating with controllers that do not clip their amps. Regular PWM controllers just pass through whatever amps they get and overheat if that is too many amps for them for too long a time.
So if your "expected amps" is 25 amps then NEC wants you to have a 30 amp controller for that 20% margin. Panels sometimes put out more than their rated amps, such as when they are cold or at high altitude, etc. The brief burst of high amps from edge of cloud effect doesn't matter AFAIK since that only lasts a few minutes at a time with those pretty white clouds going by the sun every so often.
So what is your "expected amps" anyway? If the Isc of your 140 is only 7.5a I suspect it is a mono panel with corresponding higher Voc too, since a 140w poly's Isc would be near 8.8a. If yours is poly maybe that 7.5 is Imp? (Imp does not apply to PWM)
But isn't the Blue Sky 3000 an MPPT controller? So now you have a complicated sort of "expected amps" depending on whatever watts you are getting and whatever the battery voltage is at the time, which is always changing.
So let's say your four 140s are mono with Isc of 7.5a as stated, and your expected amps will be at least as good as what PWM would get.
4 x 7.5s = 30. That's with panels aimed at high sun. Flat on roof will be less than that. It could be close with the sun overhead in summer in the south part of the USA mainland.
Your MPPT controller should clip the amps as required so no need to fuss with input if the controller is mounted properly with good ventilation cooling.
If I had four 140s I would make two pairs and get an eBay 20a PWM controller for each pair and parallel those two controllers on my battery bank. Save a bundle on controller costs and get approx the same amps.
