2 b&s cable for dual battery in rear

[AB]

Electrical genius question!

I am toying with the idea of my next project to save for a turbo, pump upgrade and of course the airbox which the second battery needs to move.

I have the perfect spot in the back and already have 2 b&s cable running back there.

Is that sufficient size to run that kind of length from cranking battery across to battery management system on passenger firewall then all the way to the back?

[Winnie]

Absolutely. Maybe not if you will be trying to crank the engine off of it but just for charging it will be more than enough.

[clubbyr8]

Have a look here, there's an app to download that will give you a lot of info on cable size, circuit protection etc. It's under circuit wizard. Seems useful....

https://www.bluesea.com/

[the evil twin]

snip...
I have the perfect spot in the back and already have 2 b&s cable running back there.

Is that sufficient size to run that kind of length from cranking battery across to battery management system on passenger firewall then all the way to the back?

Yeah, it'll be fine.

FWIW the 2nd battery on my Ute is mounted above and rear of the last cross member which is about as far as you can get without putting it in a trailer.
The voltage drop at the terminals (thru the SBI12D) between it and the Alternator is never more than .2 volts charging and it will happily crank the 6.5 chevy on its own