Please check my math..

[Crashcourse]

Good day folks! I think my math is correct and I’m hoping this will work.

I have 12 x 12V 100W Panels:
Maximum Power (Pmax): 100W
Maximum System Voltage: 700 DC
Maximum Power Voltage (Vmp): 18V
Open Circuit Voltage: 21.6V
Maximum Power Current (Imp): 5.55A
Short Circuit Current: 6.06A

And a 60A MPPT Charge Controller:
MPPT P60:
12V:open circuit voltage ≤48V(Voc) maximum. PV input power:780W
24V:Open circuit voltage ≤100V(Voc) maximum.PV input power:1560W
Automatic identification of 12V/24V system voltage
Rated charging/discharging current:60A
Maximum open circuit voltage solar panel (Voc):18V-48V(12V)/36V-96V(24V)
Power terminal:10 AWG

And a 4 string PV combiner.
What I would like to do is wire 4 sets of 3 panels in series (those 4 sets would be paralleled in the combiner, obviously) which I believe would give the Charge Controller ~54 volts at ~22 amps. The Charge Controller should then give my 24 volt battery bank (6 x 105Ah 12 Volt deep cycle LAs wired 2s3p) ~28 volts at ~44 amps, right?
Am I right about this and will it work without issues?
Thank you.

 

[Supervstech]

Firstly, the panels may achieve 24.24A so, #10 is a little small... it will work ok for a short run, but #6 would be better.

depending on battery voltage during charging, you could see 60 amps on a low bank of 20V I would size the charging conductors for 80 amps to give easy flow to the bank.

 

[Crashcourse]

Firstly, the panels may achieve 24.24A so, #10 is a little small... it will work ok for a short run, but #6 would be better.

depending on battery voltage during charging, you could see 60 amps on a low bank of 20V I would size the charging conductors for 80 amps to give easy flow to the bank.

Thank you, the panels are only 10 feet of #10 cable (13 including the PV mc4 cables) from the PV combiner, I could switch it up to #8. Less than 1.5 feet #8 from combiner to charge controller and ~2 feet #8 from charge controller to the bus bar. I could step to #6 but I don't think the PV combiner or charge controller can fit that large a gauge.
Do you think that's okay?

 

[chrisski]

If your SCC only has #10 wire max, I’d start to wonder about other specs. #10 wire is not rated to 60 amps, so that is a bit troubling. So troubling in fact, I would not want buy that. The only thing I can think of is perhaps they meant a #10 ring terminal, but I have no idea what that is amp rated for.

The second thing I see, is the MPPT SCCs I looked at did not have a different max voltage rating for PV input if it was 24 Vollt or 12 volt battery it was the same. The PWM barge controllers I looked at did have different In-N-Out ratings for 12 v and 24 v.

There is at least one company who has labeled there SCC a MPPT controller, but as you read in the small print it’s a PWM controller. If I read what you have, this company one upped that by selling a controller with wires sized for half the amperage it is supposed to produce.

 

[Crashcourse]

If your SCC only has #10 wire max, I’d start to wonder about other specs. #10 wire is not rated to 60 amps, so that is a bit troubling. So troubling in fact, I would not want buy that. The only thing I can think of is perhaps they meant a #10 ring terminal, but I have no idea what that is amp rated for.

The second thing I see, is the MPPT SCCs I looked at did not have a different max voltage rating for PV input if it was 24 Vollt or 12 volt battery it was the same. The PWM barge controllers I looked at did have different In-N-Out ratings for 12 v and 24 v.

There is at least one company who has labeled there SCC a MPPT controller, but as you read in the small print it’s a PWM controller. If I read what you have, this company one upped that by selling a controller with wires sized for half the amperage it is supposed to produce.

The SCC can accept #8 as that is what I'm using, and I think I remember asking largest and they said #6 could work, again not entirely sure if the PV combiner can accept #6. I will check and if it can I will change it up.
Thank you.

 

[Bud Martin]

The Ampacity of the wire is affeceted by the type of wire insulation rating so it will not catch on fire, I.E. 10 AWG with TEFLON or Silicone will have higher Ampacity rating than the wire that has PVC rating. the wire gauge affect the Vdrops.

 

[chrisski]

The SCC can accept #8 as that is what I'm using, and I think I remember asking largest and they said #6 could work, again not entirely sure if the PV combiner can accept #6.

Power terminal:10 AWG

What does power terminal 10 AWG mean?

The Ampacity of the wire is affeceted by the type of wire insulation rating so it will not catch on fire, I.E. 10 AWG with TEFLON or Silicone will have higher Ampacity rating than the wire that has PVC rating

I had only looked at NEC ampacity charts I could google. The charts you attach do allow 60 amps, but with an insulation rating of 125 Celsius. If 60 amps were run through it, the wire would heat to above 105 Celsius, which would boil water. My technique is to get insulation where ampacity allows 60 celsius insulation. That and anything longer than a very short length would have a higher than I want voltage loss at 60 amps.

There probably is a formula to figure out how hot a length gets based off voltage loss, but I don’t have it,

Wire length probably has

 

[Forbisher]

Is this system on a vehicle?
What's the link to the 60A MPPT? Brand?
What inverter are you using? Watts?
Link to battery?

Good day folks! I think my math is correct and I’m hoping this will work.

I have 12 x 12V 100W Panels:
Maximum Power (Pmax): 100W
Maximum System Voltage: 700 DC
Maximum Power Voltage (Vmp): 18V
Open Circuit Voltage: 21.6V
Maximum Power Current (Imp): 5.55A
Short Circuit Current: 6.06A

And a 60A MPPT Charge Controller:
MPPT P60:
12V:open circuit voltage ≤48V(Voc) maximum. PV input power:780W
24V:Open circuit voltage ≤100V(Voc) maximum.PV input power:1560W
Automatic identification of 12V/24V system voltage
Rated charging/discharging current:60A
Maximum open circuit voltage solar panel (Voc):18V-48V(12V)/36V-96V(24V)
Power terminal:10 AWG

And a 4 string PV combiner.
What I would like to do is wire 4 sets of 3 panels in series (those 4 sets would be paralleled in the combiner, obviously) which I believe would give the Charge Controller ~54 volts at ~22 amps. The Charge Controller should then give my 24 volt battery bank (6 x 105Ah 12 Volt deep cycle LAs wired 2s3p) ~28 volts at ~44 amps, right?
Am I right about this and will it work without issues?
Thank you.

 

[Crashcourse]

Is this system on a vehicle?
What's the link to the 60A MPPT? Brand?
What inverter are you using? Watts?
Link to battery?

Not in a vehicle, stationary off grid.

MPPT:

OOYCYOO MPPT Charge Controller 60 Amp 12V / 24V Auto, 60A Solar Panel Charge Regulator with LCD Display Max 100V, 780W / 1560W Input for Lead-Acid Sealed Gel AGM Flooded Lithium Battery，with Load Timer Settings(P60) : Amazon.ca

OOYCYOO MPPT Charge Controller 60 Amp 12V / 24V Auto, 60A Solar Panel Charge Regulator with LCD Display Max 100V, 780W / 1560W Input for Lead-Acid Sealed Gel AGM Flooded Lithium Battery，with Load Timer Settings(P60) : Amazon.ca

www.amazon.ca

Inverter:

https://www.amazon.ca/gp/product/B07D1LRKY5?ref=em_1p_1_ti&ref_=pe_3027290_542478430&th=1

Don't have a link to the batteries, got 'em at local auto parts store, but they are 6 X Group 31 12V 105ah Deep Cycle batteries.

 

[Forbisher]

Firstly, the panels may achieve 24.24A so, #10 is a little small... it will work ok for a short run, but #6 would be better.

.
EDIT. 3S is 54Vmp not 63.6V
10 AWG is only about 1.22% voltage drop.
3S4P
54Vmp
22A
15 feet one way distance

Click on this calculator link to change any inputs.

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

 

[Crashcourse]

10 AWG is only about 1% voltage drop.
3S4P
63.6Vmp
22A
15 feet one way distance

Click on this calculator link to change any inputs.

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

Excellent, thank you very much. According to that calculator I'll fine and using wire any larger will only decrease the drop just a few 10ths of a percent.
Thanks agin, you've been very helpful, very much appreciated!

 

[Forbisher]

Excellent, thank you very much. According to that calculator I'll fine and using wire any larger will only decrease the drop just a few 10ths of a percent.
Thanks agin, you've been very helpful, very much appreciated!

I made a mistake to see if you were paying attention. Lol
3S is 54Vmp not 63.6Vmp

Not much change in the voltage drop from 63V down to 54Vmp.
1% becomes 1.22% voltage drop so still good.

 

[Bud Martin]

What does power terminal 10 AWG mean?

I had only looked at NEC ampacity charts I could google. The charts you attach do allow 60 amps, but with an insulation rating of 125 Celsius. If 60 amps were run through it, the wire would heat to above 105 Celsius, which would boil water. My technique is to get insulation where ampacity allows 60 celsius insulation. That and anything longer than a very short length would have a higher than I want voltage loss at 60 amps.

There probably is a formula to figure out how hot a length gets based off voltage loss, but I don’t have it,

Wire length probably has

Above 105c based on what, so if you have 5" of 10 AWG wire, the wire will heat up so much that it will melt the insulation? The resistance of 10AWG 5" the Vdrops will be so low so it will not reach 105c, also if you look at the chart I provide for the TEFLON/SILICONE INSULATION of the same guage wire you will see that the ampacity is higher than the PVC at the same wire gauge, TEFLON/SILICONE insulation is a lot more expensive than PVC.
BTW, bare wire without any insulation also rated at higer Ampacity than the sawm wire gauge with insulation.

Electrical Wire Gauges

 

[Crashcourse]

I made a mistake to see if you were paying attention. Lol
3S is 54Vmp not 63.6Vmp

Not much change in the voltage drop from 63V down to 54Vmp.
1% becomes 1.22% voltage drop so still good.

Ha ha! Yeah right, particularly since I originally calculated ~54 and really should have noticed. :D
Thanks again!

 

[carl2591]

Not in a vehicle, stationary off grid.

MPPT:

OOYCYOO MPPT Charge Controller 60 Amp 12V / 24V Auto, 60A Solar Panel Charge Regulator with LCD Display Max 100V, 780W / 1560W Input for Lead-Acid Sealed Gel AGM Flooded Lithium Battery，with Load Timer Settings(P60) : Amazon.ca

OOYCYOO MPPT Charge Controller 60 Amp 12V / 24V Auto, 60A Solar Panel Charge Regulator with LCD Display Max 100V, 780W / 1560W Input for Lead-Acid Sealed Gel AGM Flooded Lithium Battery，with Load Timer Settings(P60) : Amazon.ca

www.amazon.ca

Inverter:

https://www.amazon.ca/gp/product/B07D1LRKY5?ref=em_1p_1_ti&ref_=pe_3027290_542478430&th=1

Don't have a link to the batteries, got 'em at local auto parts store, but they are 6 X Group 31 12V 105ah Deep Cycle batteries.

no such thing as a true deep cycle group 31, 12v battery of 105 ah.. they are the RV/Marine label crap.. you are better to get real lithium 100 ah is actually 90 usable AH vs the 105 you have or or getting which is really a 55 ah battery. the cost is about the same for more battery.. most of your true deep cycle batteries are 6 or 8 volts.. like the trojan t-105 225 ah 6 volt battery that fricken weighs 75 lbs each.

justsaying..