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2s 3p 2p is this feasible? flexmax 80 amp solar charge controller

michael d

off-grid solar pilgrim
Joined
Dec 15, 2019
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728
Location
South Dakota, USA
Can it be done safely without big problems?
327-watt solar panels with 64.9 VOC and 6.46 amps ISC.
can I put 2 in series = 129.8 volts @ 6.46 amps ISC,
then put 3 sets of 2 panels (wired in series) in parallel = 129.8 volts @ 19.38 amps ISC,
then put 2 of those 6-panel arrays in parallel again = 129.8 volts @ 38.76 amps ISC?
the outback flexmax 80 solar charge controller is up to 150 volts DC input not to exceed 64 amps input as I read it and rated at 80 amps output (48 volt battery, the pv array input limit is 4000 watt from the pv array)
every 6-panel array is 1962 watts (or 3924 watts for 12 panels).

2 panels in series; (volts (64.9+64.9)adds up to 129.8 volts, while the amps remains the same @6.46 amps)
3 sets of 2 in series wired in parallel; = array of 6 (volts stay the same @ 129.8 volts, while the amps add up 6.46+6.46+6.46 now equals 19.38 amps)
then 2 arrays of 6 panels each wired in parallel for one larger array of 12 panels. volts stay the same @129.8 volts but the amps add up 19.38+19.38 now equals 39.76 amps)

what do you think?
I have 2 of the 80 amp outback flex max charge controllers and 40 panels. or am I stuck with only 8 panels per charge controller?
 
Looks like you have the math correct and its all well within max input volts and amps.
Is there a reason you suspect it won’t work?
 
You mean 2s6p? Nothing wrong with that, either physically wired as all 6 pairs in parallel, or two sets of 2s3p (and perhaps routed from different locations with fatter wires.)
Each of the 6 strings should have a fuse no larger than what the label says. Wire carrying 3 or 6 parallel strings should be sized for 1.56x (?) x 3 (or 6) x Isc, i.e. well above maximum expected current.

Is this a 48V system?
80 amp charge controller would be just about right for 327 x 12 or 3924W (stc) going into a 48V battery.
You can probably go a bit above, because it's not a hard limit, and actual power from panel will normally be a bit less.
You can put in 150% of that if half the panels are oriented 90 degrees different from the others - 1/sqrt(2)

I don't see an input current limit, although it may have max Isc somewhere.

You've got 40 panels - I think you can put 20 on each charge controller, just using 2 or possible 3 orientations (Summer 10:00 AM, Summer 4:00 PM, Winter 1:00 PM, for instance)

Check temperature coefficient and record cold temperature for your location, but I think it is just under the 150V absolute max of Flexmax 80.
 
Looks like you have the math correct and its all well within max input volts and amps.
Is there a reason you suspect it won’t work?
I would put 3 sets of 2 into a midnight solar combiner box (mnpv3 only holds 3 breakers)with 15 amp dc breaker to each set of 2 PV panels. then I would run the two separate six-panel arrays to a second combiner in parallel using (10 gauge solar PV wire) again increasing the amperage from 19.38 to 38.76 amps. I would have to use a dc breaker between this parallel combined 12-panel array rated at least (38.76 x 1.56 = 60.47) 60.47 amps and a larger gauge wire to the outback flexmax 80 solar charge controller? I have 80 amp midnight solar panel mount breakers for this.
I read that I have to have all parallel before they go into the solar charge controller(can't have 2 separate array wires going into the outback flexmax 80).
The reason to have 2 separate 6-panel arrays and a second parallel is to keep the amperage and wire size down. But when I parallel the second time and the amps increase to 38.76 amps the wire size will have to be increased to what size? it says I can use up to 2 gauge to the wire terminals in the outback flex max so I will use this size wire ( 2 gauge has an ampacity capacity of approximately 95 amps - bigger wire is best) so I use the biggest as I have some available.
the outback flexmax 80 charge controllers and the battery bank is located in an insulated 8 foot by 8 foot outside solar shed due to safety concerns to keep it away from children.
yes, this is a 48-volt lithium iron phosphate battery system ( two 24 volt LiFePO4 batteries wired in series to make a 48-volt battery).
the reason for the original question is: one paralleling the 1st array of 6 panels to the second array of 6 panels. 2S 3P 2P
I can use 10 gauge solar PV wire which is rated up to 35 amps but can safely be breakered at 30 amps the way I read it on each array of 6 as they are combined in parallel the second time to make the 38.76 amps out going to the outback flexmax 80 solar charge controller. i would put the 80 amp panel mount breaker in between the second combined 12-panel array and the outback flexmax solar charge controller.
All panels will be mounted facing south at a 45-degree angle (possibly change angle depending on the season - not sure of this part yet) in South Dakota, the southern part. A total of 12 panels to each of the outback flexmax solar charge controllers.
The concern or possibly overthinking is the parallel after parallel. This is strictly off-grid. no grid tie as the utility does not do net metering in South Dakota.
Thanks for all input as I put it all on paper and in practice.
 
You mean 2s6p? Nothing wrong with that, either physically wired as all 6 pairs in parallel, or two sets of 2s3p (and perhaps routed from different locations with fatter wires.)
Each of the 6 strings should have a fuse no larger than what the label says. Wire carrying 3 or 6 parallel strings should be sized for 1.56x (?) x 3 (or 6) x Isc, i.e. well above maximum expected current.

Is this a 48V system?
80 amp charge controller would be just about right for 327 x 12 or 3924W (stc) going into a 48V battery.
You can probably go a bit above, because it's not a hard limit, and actual power from panel will normally be a bit less.
You can put in 150% of that if half the panels are oriented 90 degrees different from the others - 1/sqrt(2)

I don't see an input current limit, although it may have max Isc somewhere.

You've got 40 panels - I think you can put 20 on each charge controller, just using 2 or possible 3 orientations (Summer 10:00 AM, Summer 4:00 PM, Winter 1:00 PM, for instance)

Check temperature coefficient and record cold temperature for your location, but I think it is just under the 150V absolute max of Flexmax 80.
I think I am limited to 4000 watts from the PV array into the outback flexmax 80 solar charge controller using a 48-volt battery bank.
Thanks for the input as I work this all out.
 
I think I am limited to 4000 watts from the PV array into the outback flexmax 80 solar charge controller using a 48-volt battery bank.
Thanks for the input as I work this all out.

You can put in PV panels totaling 6000W to make an array with 4000W. If strings have different angles, peak power at any given moment will be less, because area facing the sun is less. For instance, if two sub-arrays have 90 degree angle between them, area presented is proportional to hypotenuse of the triangle (as compare to sum of the legs.) So about 0.7 times 6000W, 4200W. But it makes more power when the sun is off-angle because it presents more area earlier and later in the day. Similar effect to a 1-axis tracker, but without the moving parts. Cheaper, too, and more reliable.

This will reduce maximum charge current into your batteries, and reducing cycling throughout the day. Also leave them with more charge as night approaches.
 
I think I am limited to 4000 watts from the PV array into the outback flexmax 80 solar charge controller using a 48-volt battery bank.
Thanks for the input as I work this all out.

Along the lines of what Hedges is explaining in detail, in general, it's common to "over panel" a controller to get peak power over a longer period of time as opposed to a single peak at high noon. As long as you don't exceed its voltage and current input limits, it will only pull what it needs to charge your batteries at 80A. As an example, my Victron 250/100 could handle a 250V * 70A (current limit) = 17,500W array, BUT it can only charge at 100A. At 48V, it's limited to 5800W.
 
The concern or possibly overthinking is the parallel after parallel.
Had you worded you original post differently, nobody (or maybe just me?) would have batted an eye at your configuration (assuming correct of course).
If you asked about “combing 2 arrays of 2s 3p panels” for a Flexmax 80 SCC, it seems completely routine.

Your reasoning (overthinking?) for your configuration was different from what i expected but the fact remains, you can combine in many different ways to suit your needs. You just need to handle the specific amps and volts everywhere along the way (wires and fusing).

My guess was that you had arrays pointing/mounted in different directions.
 
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I read that I have to have all parallel before they go into the solar charge controller(can't have 2 separate array wires going into the outback flexmax 80).

I think there are ways to accomplish that.

Supposedly, we aren't supposed to put two wires in one screw terminal. Except when it is designed for it, like some set screw "wire nuts" I have. Practically speaking (and neglecting any codes), I find that multiple stranded wires in one terminal works fine.

To do it in compliance with code:
1) use a split bolt to join the two wires, inside Flexmax enclosure.
6 awg is going to be sufficient for 60A, maybe even higher for a single wire inside the enclosure rather than in a cable.
Depending on your awg, you might feed one wire from a combiner into the Flexmax terminal and use a split bolt to join the second.
Or, use a split bolt to join two wires to one heavier one.
Wrap with rubber tape, followed by vinyl tape.

2) use a ferrule meant for two wires. Insert that ferrule into the Flexmax terminal.
 
I think I am limited to 4000 watts from the PV array into the outback flexmax 80 solar charge controller using a 48-volt battery bank.
Thanks for the input as I work this all out.
It would essentially be 2 arrays 2S3P Total of 6 panels one array, and 6 panels from the second Array in 2S3P again. the flexmax 80 only allows one set of PV input wires so that is why I wanted to combine the 2 arrays before they enter the Outback FlexMAx 80 amp solar charge controller. it is an 80 amp controller.
 
Had you worded you original post differently, nobody (or maybe just me?) would have batted an eye at your configuration (assuming correct of course).
If you asked about “combing 2 arrays of 2s 3p panels” for a Flexmax 80 SCC, it seems completely routine.

Your reasoning (overthinking?) for your configuration was different from what i expected but the fact remains, you can combine in many different ways to suit your needs. You just need to handle the specific amps and volts everywhere along the way (wires and fusing).

My guess was that you had arrays pointing/mounted in different directions.
yes, it is a bit difficult to word it correctly. all panels face the same south direction at this point but I may change that to get some early sun and some late sun, split to get more without a tracker. that sounded like a good idea.
 
Had you worded you original post differently, nobody (or maybe just me?) would have batted an eye at your configuration (assuming correct of course).
If you asked about “combing 2 arrays of 2s 3p panels” for a Flexmax 80 SCC, it seems completely routine.

Your reasoning (overthinking?) for your configuration was different from what i expected but the fact remains, you can combine in many different ways to suit your needs. You just need to handle the specific amps and volts everywhere along the way (wires and fusing).

My guess was that you had arrays pointing/mounted in different directions.
ok thanks
 
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