Help choosing a charge controller

faccnator

Hey all. Been reading for a long time. First post.

Looking for a charge controller suggestion.

I have 7ea Renogy 270w panels coming and I am trying to choose a charge controller. I have a 24 volt battery bank.

I am drawn to the Schneider electric products but I’m not sure if their charge controllers are worth the price.

Any suggestions? I use an old Xantrex SW4024 with an Outback Autotransformer for 240v. To this point I have only been using it for backup.

I’m in Florida.

Thanks again!

Photowhit

Quick, Buy one more panel or send 1 back...

7 is a very ugly number for panels. It's prime so you can run them all in parallel, which you can't because the voltage is to low or you can run a single string of 7 panels, which would require a high voltage charge controller which will cost big bucks. Hopefully you are in south Florida and are buying the panels from Sun Electric in Miami and can just go down and pick up 1 more panel and run 4 strings of 2 panels. Though I haven't seen any Renogy panels there in quite a while.

faccnator

Actually 6 will fit perfect on my unobstructed southern elevation so I will return one. Thank you. Does that help with suggestions? I was initially going to install them in series to keep the wire size down but I think you are suggesting not to due to high voltage. I’m trying to pick my poison

faccnator

Also they are 24volt panels

Photowhit

We don't know the specs on your panels, they could be 60 cell panels for a vmp of around 30-32volts and a VOC of around 38 volts, or they could be 72 cell panels with a VMP of around 35-38 and a VOC of around 45 volts

Either case would put the VOC of a string of 6 panels above the safe operating range of most charge controllers. 6x38=228 volts and 6x45=270 volts. Only reason to run them in a single long string and pay the price for a high voltage charge controller would be if they will be a long distance from the charge controller.

Lots of good choices, you will have an array of  270 x 6= 1620 watts so an effective potential of about 1620/29=56 amps, so pretty much any 60 amp or higher charge controller would work.

I have used Midnite Classics and like them, you can create triggers to turn on loads once it reaches a certain point in it's charging. It will also leave you some room for expansion being able to handle around 94 amps depending on configuration. Schneider makes good products. As does Morningstar and Outback.

Midnite Classic (about 92 amp at 24 volts) $550;
https://www.solar-electric.com/midnite-solar-classic-150-sl-charge-controller.html

Outback FM80 (80 amps) $500 (requires addition equipment for some programing);
https://www.solar-electric.com/outback-power-flexmax-fm80-150-mppt-charge-controller.html

Morningstar MPPT 60(60 amps), $550;
https://www.solar-electric.com/motr60ampmps.html

Schneider Conext MPPT 60(60 amps), $546;
https://www.solar-electric.com/xaxwmp60amps.html

Photowhit

Forgot to say, so you can run them as 2 strings and combine at the panels and make 1 run to the charge controller. You would loss a bit due to the higher conversion (from high voltage to 24 volts) but it wouldn't require a combiner box and fuses or breakers.  

...Or you could run 3 strings of 2 panels, which would allow the charge controllers to run more efficiently but require a combiner box at the panels. 

faccnator

Gosh I just can’t thank you enough for the info. I hope that soon I have something to contribute. Here are the specs on the panels.


Specifications
Maximum Power: 270W Maximum System Voltage: 1000 VDC (UL)
Optimum Operating Voltage (Vmp): 31.40V Open-Circuit Voltage (Voc): 38.60V
Optimum Operating Current (Imp): 8.60A Short-Circuit Current (Isc): 9.03A
Maximum Series Fuse Rating: 15A Weight: 42.8lbs
Dimensions: 64.96 x 39.25 x 1.57 inch


How do I decide the wiring configuration that is right for me? How many panels in a string?

mike95490

I'll second the 3 strings of 2 panels.  Needs more copper for the higher panel amps, but runs the charge controllers in a more favorable voltage ratio.   You will want a combiner / breaker panel anyway, so you can easily do troubleshooting  and such.

faccnator

Ok so last question for tonight. Maybe. If I go with the 3 strings of 2 panels. What size wire do I need from the combiner to the charge controller? Approximately 20 feet

Estragon

At 20', strings of 2 are likely a good choice.

You can look at voltage drop for different wire sizes at
https://www.calculator.net/voltage-drop-calculator.html

mcgivor

Photowhit said:

We don't know the specs on your panels, they could be 60 cell panels for a vmp of around 30-32volts and a VOC of around 38 volts, or they could be 72 cell panels with a VMP of around 35-38 and a VOC of around 45 volts

Either case would put the VOC of a string of 6 panels above the safe operating range of most charge controllers. 6x38=228 volts and 6x45=270 volts. Only reason to run them in a single long string and pay the price for a high voltage charge controller would be if they will be a long distance from the charge controller.

Lots of good choices, you will have an array of  270 x 6= 1620 watts so an effective potential of about 1620/29=56 amps, so pretty much any 60 amp or higher charge controller would work.

I have used Midnite Classics and like them, you can create triggers to turn on loads once it reaches a certain point in it's charging. It will also leave you some room for expansion being able to handle around 94 amps depending on configuration. Schneider makes good products. As does Morningstar and Outback.

Midnite Classic (about 92 amp at 24 volts) $550;
https://www.solar-electric.com/midnite-solar-classic-150-sl-charge-controller.html

Outback FM80 (80 amps) $500 (requires addition equipment for some programing);
https://www.solar-electric.com/outback-power-flexmax-fm80-150-mppt-charge-controller.html

Morningstar MPPT 60(60 amps), $550;
https://www.solar-electric.com/motr60ampmps.html

Schneider Conext MPPT 60(60 amps), $546;
https://www.solar-electric.com/xaxwmp60amps.html

Morningstar and Schneider are passively cooled, no fan noise, Midnight and Outback have fans, all good controllers just something to consider.

Raj174

With 3 strings of 2, the cable run from combiner to the controller will have 62 volts at about 26 amps on it.

Photowhit

faccnator

Everyone thank you so much for showing me how to use the tools and calculators. I’ll give everyone an update when they are up and running. Thanks again.