I have 2x 250 watt panels wired in series going into a 100/30 controller - this connects to a battery bank consisting of 2 x 12 volt 140ah batteries.
I have a 2nd 100/30 controller with 2 more panels exactly the same...... both seem fine individually, and work well.
BUT
as soon as I connect both to the battery bank, one controller drops from its normal wattage to around 70-80 watts. (I also notice while the volts stay the same, the Amps also drop way down to around 0.5-0.8)
Why does this happen ?
is it normal ?
thanks for your help.