I've figured out and purchased all the components that I can afford at this point for a new system -- but one array configuration question keeps nagging at me. I have 9 new identical panels with these STC-rated specs:
Pmax = 136w
Vmp = 33.0v
Current@Pmax(Imp)= 4.1a
Open-circuit Voltage (Voc) = 46.2v
I already have a 24v AGM Battery Bank (currently 210ah) and do not want to go to 48v.
And I already have a Morningstar TS-MPPT-45 charge controller which takes PV output up to 150v and 1200 watts @ 24v and deliver a maximum of 45a charging current (this is the most controller I can afford... a bigger controller just isn't in the budget).
I'm lucky -- there is only 20 feet of distance from my panels to my charge controller in the house and the batteries are in the same closet. I'm in North Florida with quite a few 5-to-6 hour peak sun days during the year. Really cold panels generating over-voltage is not an issue for me either.
THE QUESTION: What's the best approach to connecting the panels together as a single array for input into this controller and charging this battery bank -- go all parallel or use a series/parallel combination? With the short run from the panels to the controller, wire cost is not really an issue. I know that in general the more amps you can throw at a battery bank the better -- but is it better to hit my controller with a high amperage current by connecting all 9 panels in parallel or to connect the panels in a series/parallel combination and input a lot of excess voltage at lower amperage and let the MPPT covert all that excess voltage to charging range current? Unless I'm missing something, I have two options:
Connecting all 9 panels in parallel would hit the controller with 41 amps at 33v at peak sun -- the controller would still have 4 amps of excess charging capability and a small amount of excess voltage coming into do its MPPT thing with.
Connecting 3 panels in series to create 3 groups which would then be connected in parallel. That would hit the controller with only 12.3 amps but a kickin' 99 volts -- tons of excess voltage for the MPPT function to work on, but maybe more than it can reasonably be expected to convert to the 25-28v charging range for my 24v battery bank?
Which of the above approaches is going to work best/most efficiently with the least amount of wear and tear on the controller -- or does it really make any difference? If some other series/parallel combination would strike a more suitable balance I could get one more identical panel for a total of 10, although that would put me over my controller's stated maximum of 1200 watts of PV input at peak.
Any thoughts or experience with the Amps vs. Volts choice where MPPT is concerned would be most helpful and appreciated.
-- J.R.
Pmax = 136w
Vmp = 33.0v
Current@Pmax(Imp)= 4.1a
Open-circuit Voltage (Voc) = 46.2v
I already have a 24v AGM Battery Bank (currently 210ah) and do not want to go to 48v.
And I already have a Morningstar TS-MPPT-45 charge controller which takes PV output up to 150v and 1200 watts @ 24v and deliver a maximum of 45a charging current (this is the most controller I can afford... a bigger controller just isn't in the budget).
I'm lucky -- there is only 20 feet of distance from my panels to my charge controller in the house and the batteries are in the same closet. I'm in North Florida with quite a few 5-to-6 hour peak sun days during the year. Really cold panels generating over-voltage is not an issue for me either.
THE QUESTION: What's the best approach to connecting the panels together as a single array for input into this controller and charging this battery bank -- go all parallel or use a series/parallel combination? With the short run from the panels to the controller, wire cost is not really an issue. I know that in general the more amps you can throw at a battery bank the better -- but is it better to hit my controller with a high amperage current by connecting all 9 panels in parallel or to connect the panels in a series/parallel combination and input a lot of excess voltage at lower amperage and let the MPPT covert all that excess voltage to charging range current? Unless I'm missing something, I have two options:
Connecting all 9 panels in parallel would hit the controller with 41 amps at 33v at peak sun -- the controller would still have 4 amps of excess charging capability and a small amount of excess voltage coming into do its MPPT thing with.
Connecting 3 panels in series to create 3 groups which would then be connected in parallel. That would hit the controller with only 12.3 amps but a kickin' 99 volts -- tons of excess voltage for the MPPT function to work on, but maybe more than it can reasonably be expected to convert to the 25-28v charging range for my 24v battery bank?
Which of the above approaches is going to work best/most efficiently with the least amount of wear and tear on the controller -- or does it really make any difference? If some other series/parallel combination would strike a more suitable balance I could get one more identical panel for a total of 10, although that would put me over my controller's stated maximum of 1200 watts of PV input at peak.
Any thoughts or experience with the Amps vs. Volts choice where MPPT is concerned would be most helpful and appreciated.
-- J.R.
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