Battery Cable advice please

[Albert Ross]

My domestic battery bank is made up of 4 x 80 AH batteries in 2 banks of 2 batteries.
The 2 banks of 2 batteries are 3 metres apart.
What size wires (cross section in sq mm) should I use to connect the two banks please?
Using "the biggest possible" would be quite expensive !
Thanks.

 

[JumbleDuck]

My domestic battery bank is made up of 4 x 80 AH batteries in 2 banks of 2 batteries.
The 2 banks of 2 batteries are 3 metres apart.
What size wires (cross section in sq mm) should I use to connect the two banks please?
Using "the biggest possible" would be quite expensive !
Thanks.

It depends on what you run from them.

 

[Albert Ross]

It depends on what you run from them.

Everything (lights, instruments, Webasto, fridge etc) except the starter motor runs off the domestic / "home" bank.

 

[pvb]

In that case, I'd use 35 sq mm cable. It would also help in maximising charge efficiency if you could take the main positive from one end of the bank, and the main negative from the other end.

 

[Albert Ross]

In that case, I'd use 35 sq mm cable. It would also help in maximising charge efficiency if you could take the main positive from one end of the bank, and the main negative from the other end.

Thanks.
As it would be very difficult to move the main negative or positive as you suggest, do you think there would there be any advantage in using 50 sg mm cable?

 

[Albert Ross]

In that case, I'd use 35 sq mm cable. It would also help in maximising charge efficiency if you could take the main positive from one end of the bank, and the main negative from the other end.

Thanks.
As it would be very difficult to move the main negative or positive as you suggest, do you think there would there be any advantage in using 50 sg mm cable?

 

[pvb]

Thanks.
As it would be very difficult to move the main negative or positive as you suggest, do you think there would there be any advantage in using 50 sg mm cable?

With the size of the batteries, and the sort of typical loads you've described, the cables are probably unlikely to carry much more than 20A in most circumstances. 35 sq mm cable would give a volt drop of less than 0.1v so I reckon that would be acceptable. Going up to 50 sq mm cable would only reduce the volt drop by about 20mv.

 

[JumbleDuck]

Thanks.
As it would be very difficult to move the main negative or positive as you suggest, do you think there would there be any advantage in using 50 sg mm cable?

You don't have to move the main wires. Just run negative to bank 1 and onto bank 2, positive past bank 1 to bank 2 and then back to bank 1 again.