Voltage vs. PWM controller & wire size
Ok, there is a recent thread out there MPPT vs. PWM and some post were a little confusing to me. Instead of hijacking his thread I started a new one. My set up is two 208 watt Sony panels with 28....
Forum Discussion
(one panel)
In bright light the panel will produce 7amps (208 watts /29v, adjust the amps scale on the graph below). PWM will operate at battery volts and 7 amps (input) and ouput the same. Mppt has the ability to accept all the watts at the peak power point and transform this to battery voltage (208 watts/14 = 14+amps.
So while charging at 14v, PWM yields 7 amps * 14v while MPPT yields 208 watts less the ineffiencies of the 'transforming'. ie PWM would limit the panel's power to about 1/2.
Your voltage drop calc should use 7 amps for the input to the mppt controller.
and 14 amp from the controller to the batteries. PWM would be 7A both sides of the controller.
because the controller turns on and off to limit power when the battery approaches full charge, the controller needs to be rated to accept the Voc of the panel(s) and how connected, series exceeds the limit of that controller!
Parrellel two panels, PWM yields 14A. Series PWM yields 7A
Solar panel open-circuit voltage..................55V maximum
Solar panel nominal voltage.......................12V -
24V, matched to the battery voltage:
Vpp about 16-18+Volts for
12v systems, Vpp about 32-36+ for 24V systems
in short, for 12v system, wrong controller.
In bright light the panel will produce 7amps (208 watts /29v, adjust the amps scale on the graph below). PWM will operate at battery volts and 7 amps (input) and ouput the same. Mppt has the ability to accept all the watts at the peak power point and transform this to battery voltage (208 watts/14 = 14+amps.
So while charging at 14v, PWM yields 7 amps * 14v while MPPT yields 208 watts less the ineffiencies of the 'transforming'. ie PWM would limit the panel's power to about 1/2.
Your voltage drop calc should use 7 amps for the input to the mppt controller.
and 14 amp from the controller to the batteries. PWM would be 7A both sides of the controller.
because the controller turns on and off to limit power when the battery approaches full charge, the controller needs to be rated to accept the Voc of the panel(s) and how connected, series exceeds the limit of that controller!
Parrellel two panels, PWM yields 14A. Series PWM yields 7A
Solar panel open-circuit voltage..................55V maximum
Solar panel nominal voltage.......................12V -
24V, matched to the battery voltage:
Vpp about 16-18+Volts for
12v systems, Vpp about 32-36+ for 24V systems
in short, for 12v system, wrong controller.
