I just bought my second 40A MPPT solar charge controller 4215BN to expand my off grid solar system from 800w to 2000w. I read somewhere that f I am using a second controller, I should have an equal amount of watts and volts going through it as the other. Is that true? The charge controllers are identical twins.
More compelling is my concern at running the second controller through my combiner box, where my system is set up now. Two 400w 48v arrays of 12v, 100w panels in parallel go through my combiner box. The negative wire screws onto the ground bar at the top, while the hot wire goes through a 20a breaker to the insulated (not grounded) hot bar near the bottom by the breakers. The charge controller panel inputs are attached by wires to the same ground and hot bar of the combiner box, so the panel current goes to the charge controller through the combiner box.
The new addition: four 300w, 24v panels will provide 1200w in two 48v arrays in parallel (or I can wire the arrays into the combiner box separately, which also parallels them.), Open circuit = 40v per panel, short circuit just under 10 amps. Each two panels in series = about 80v open circuit. My existing arrays also have an open circuit of 80v. If I run the new system through the combiner box, the energy from all panels will be combined on the hot and ground bars and be connected to both charge controllers at the same time. That should parallel two 80v open circuit systems. The max voltage for my controllers is 138v. Will this put too much voltage on the controllers, or will the voltage remain at 80 while amps increase?
Also, my current arrays produce up to 11 amps. The additional panels add 10 amps per panel or 10 amps per two in series equalling 20 amps when joined in parallel with the other two 24v panels attached in series to form a 48v array. If my calculations are correct, that should add up to 31 amps on my 40 amp chargers.
I have room for another array of four 100w, 12v panels on the structure I built for my new panels. If I add another 400w, 48v array to my system, that will add an additional 5.4 amps each 100v panel is rated at, while retaining the 48v, 80v open circuit to the charge controllers. Total: 80v open circuit on a charge controller rated for 138v open circuit and 36.4 amps when charge controller is rated 40 amp.
Could I do this with just one charge controller, or is there an advantage in using two through a common combiner box?
More compelling is my concern at running the second controller through my combiner box, where my system is set up now. Two 400w 48v arrays of 12v, 100w panels in parallel go through my combiner box. The negative wire screws onto the ground bar at the top, while the hot wire goes through a 20a breaker to the insulated (not grounded) hot bar near the bottom by the breakers. The charge controller panel inputs are attached by wires to the same ground and hot bar of the combiner box, so the panel current goes to the charge controller through the combiner box.
The new addition: four 300w, 24v panels will provide 1200w in two 48v arrays in parallel (or I can wire the arrays into the combiner box separately, which also parallels them.), Open circuit = 40v per panel, short circuit just under 10 amps. Each two panels in series = about 80v open circuit. My existing arrays also have an open circuit of 80v. If I run the new system through the combiner box, the energy from all panels will be combined on the hot and ground bars and be connected to both charge controllers at the same time. That should parallel two 80v open circuit systems. The max voltage for my controllers is 138v. Will this put too much voltage on the controllers, or will the voltage remain at 80 while amps increase?
Also, my current arrays produce up to 11 amps. The additional panels add 10 amps per panel or 10 amps per two in series equalling 20 amps when joined in parallel with the other two 24v panels attached in series to form a 48v array. If my calculations are correct, that should add up to 31 amps on my 40 amp chargers.
I have room for another array of four 100w, 12v panels on the structure I built for my new panels. If I add another 400w, 48v array to my system, that will add an additional 5.4 amps each 100v panel is rated at, while retaining the 48v, 80v open circuit to the charge controllers. Total: 80v open circuit on a charge controller rated for 138v open circuit and 36.4 amps when charge controller is rated 40 amp.
Could I do this with just one charge controller, or is there an advantage in using two through a common combiner box?
Comment