Series/Parallel wiring (24V) and wire sizing

[31ectr0nicb0b]

The following is my build thread in case anyone wants to see more detail, not that there is much just starting, pretty much a noob.

Daddy's Barn [Outback FlexPower One (VFXR3524A-01) Battle Born BBGC2H]

My kids and I are building a barn since the pandemic and its at a stage where its ready for some power. I'll be getting a standing seam metal roof installed soon so I need to address the PV DC input and array size. I am planning on doing a series-parallel connection for [4] 24V banks with...

diysolarforum.com

My main questions are:

• Given my setup, 24V battery bank (400Ah 24V), FlexPower One, VFXR3524 inverter and FM 80 charge controller, does this wiring plan for the batteries look ok? I have seen wiring diagrams where the parallel wiring is created first between [2]12V batteries and then series wiring, according to my plan, I am doing the opposite. Any pros cons?
  • I am thinking this way depicted below would be the best way in terms of using least amount of wire.
• Where do I run the main positive (+) and negative (-) to the FlexPower One? Off the right side of the image below?
  • And what gauge wire should these mains be?
• I am planning on using 1/0 wire for all of the connections. Adequate?

 

[sunshine_eggo]

My main questions are:

• Given my setup, 24V battery bank (400Ah 24V), FlexPower One, VFXR3524 inverter and FM 80 charge controller, does this wiring plan for the batteries look ok? I have seen wiring diagrams where the parallel wiring is created first between [2]12V batteries and then series wiring, according to my plan, I am doing the opposite. Any pros cons?
  • I am thinking this way depicted below would be the best way in terms of using least amount of wire.

Looks fine.

• Where do I run the main positive (+) and negative (-) to the FlexPower One? Off the right side of the image below?

No.

Your main leads need to draw from opposite ends. Main (-) on one end and the main (+) on the other end.

• • And what gauge wire should these mains be?

Sized for the current they need to transfer.

Interconnects and main leads need to be the same size.

• I am planning on using 1/0 wire for all of the connections. Adequate?

Is that sufficient to handle the needed current?

 

[31ectr0nicb0b]

Oops, forgot to give those details, so VFXR3524 inverter is 3500W output and it is a 24V battery system, 3500/24 is ~145A.

The Southwire voltage drop app on my phone for 10' run (I probably wont have more than a 5' main (+-) run from batteries to inverter) for 24V and 3% voltage drop and 150A is 1/0 AWG.

Does the image above look good now for the main +,- at opposite ends of the battery bank?

 

[sunshine_eggo]

Oops, forgot to give those details, so VFXR3524 inverter is 3500W output and it is a 24V battery system, 3500/24 is ~145A.

3500W/25.6V/.85 = 161A

85% efficient. Yes, your inverter has a higher efficiency spec than 85%, but that's at about 30% rated power. It decreases as power output increases. 85% is a conservative

The Southwire voltage drop app on my phone for 10' run (I probably wont have more than a 5' main (+-) run from batteries to inverter) for 24V and 3% voltage drop and 150A is 1/0 AWG.

1/0 would yield a 1.24% voltage drop. You would need to get 90°C or better rated cable. 60 or 75°C cable does not have sufficient rating to handle 161A.

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

You have a lot of connections. Make sure all connections are properly torqued.

Does the image above look good now for the main +,- at opposite ends of the battery bank?

Yes.

 

[31ectr0nicb0b]

Thanks. For a safety factor sake, I may just go with 2/0 if I'm unable to find a 90C rated 1/0.

 

[sunshine_eggo]

Thanks. For a safety factor sake, I may just go with 2/0 if I'm unable to find a 90C rated 1/0.

Most marine or battery UL listed cable is 105°C or better.