Forum Discussion

MrWizard's avatar
MrWizard
Moderator
Jun 24, 2015

why don't Solar controller mfg/sellers use honest ratings

example most 30amp controllers are listed at 390w of panels and 40amp controllers at 500w of panels but we don't charge batteries at 12.0v we charge at 14v or higher 14v*30 amps 420w output, ...
BFL13's avatar
BFL13
Explorer II
Jun 27, 2015
It is not 1.25 for voltage as such, but you do have to leave margin in your controller's total Voc input limit for when Voc is higher than rated at STC.

You can calculate that from the coefficient in the panel spec for the coldest you expect to be using it.

Mr Wiz--"working amps" with PWM is Isc NOT the lower Imp figure you would use with MPPT. You would see this if you had tracking panels and checked panel Isc (disconnected) with amps to the battery (connected) --same amps amount.

About Technical Issues

Having RV issues? Connect with others who have been in your shoes.24,188 PostsLatest Activity: Jan 19, 2025