Hello. I am new here.
I have been using 50 watts of solar for an off grid weekend cabin since 2009 but always 12v.
I usually run less than 4 amps total and do that mostly direct from the batteries not the load terminal on my controller. Some CFL or leds, occasionally a 12v tv or small 12v pump.
These new panels will let me increase the current watts by a factor of 7 so she can charge her phone, computer, hot spot and whatever else she has in mind and I can keep the batteries full. I'm afraid she will find out there are 12v electric blankets.
the new panels are two 2 year old 175W panels, suntech, for 50.00 each. They are 24V
Label says Pmax 175W, Vmp 35.2, Imp 4.95, Open Circuit 42V. Isc 5.2A
I can use them together or separate 1 bank or 2 banks. 2 banks are better since batteries are similar but 2 years apart. Or I can use 2 panels on 1 bank and swap out periodically. Banks are 2 @ 125AH AGM batteries each x 2 banks.
I am trying to figure out how to size the controller, by the panels or batteries.
In other words:
175W at 35.2v = 4.97A x 2 panels = 9.94A. But when i convert that to 12V it will become 19.88 Amps except that the controller will charge at 12V but more likely 13.7 prox depending on the battery type and status. so 12/13.7 = .876 x 19.88 total Amps at 12v = 17.41 total amps max at ideal conditions. From this it looks like I could use two 10 A controllers or one 20 Amp controller. I think I would rather have 2 controllers for 2 banks and only combine the banks if I had a larger load for a short time. MPPT.
Am I right to ignore the open circuit voltage and amps in this calculation?
Or:
I could series connect two batteries and get 24v and use a dc-dc inverter to make 12v to feed the loads. If I did that would I lose much using a PWM 24v converter and the inverter. could i run both banks into the same inverter,
thank you in advance for the help.
I have been using 50 watts of solar for an off grid weekend cabin since 2009 but always 12v.
I usually run less than 4 amps total and do that mostly direct from the batteries not the load terminal on my controller. Some CFL or leds, occasionally a 12v tv or small 12v pump.
These new panels will let me increase the current watts by a factor of 7 so she can charge her phone, computer, hot spot and whatever else she has in mind and I can keep the batteries full. I'm afraid she will find out there are 12v electric blankets.
the new panels are two 2 year old 175W panels, suntech, for 50.00 each. They are 24V
Label says Pmax 175W, Vmp 35.2, Imp 4.95, Open Circuit 42V. Isc 5.2A
I can use them together or separate 1 bank or 2 banks. 2 banks are better since batteries are similar but 2 years apart. Or I can use 2 panels on 1 bank and swap out periodically. Banks are 2 @ 125AH AGM batteries each x 2 banks.
I am trying to figure out how to size the controller, by the panels or batteries.
In other words:
175W at 35.2v = 4.97A x 2 panels = 9.94A. But when i convert that to 12V it will become 19.88 Amps except that the controller will charge at 12V but more likely 13.7 prox depending on the battery type and status. so 12/13.7 = .876 x 19.88 total Amps at 12v = 17.41 total amps max at ideal conditions. From this it looks like I could use two 10 A controllers or one 20 Amp controller. I think I would rather have 2 controllers for 2 banks and only combine the banks if I had a larger load for a short time. MPPT.
Am I right to ignore the open circuit voltage and amps in this calculation?
Or:
I could series connect two batteries and get 24v and use a dc-dc inverter to make 12v to feed the loads. If I did that would I lose much using a PWM 24v converter and the inverter. could i run both banks into the same inverter,
thank you in advance for the help.
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