Wiring question

Question, do you need to use the same size wire for both the positive and negative leads to the battery. I’m running 1/0 from the positive side of the battery to a DC - DC charger. I had already made up a 4 gauge lead for the negative side of the battery, with a 250amp bus bar inline, to tie all my negative leads together?
Thanks in advance, Russ

Both the negative and positive need to be large enough to handle the the current. You also have to run large enough wire (both pos and neg) to ensure the voltage drop is acceptable.

Have said that 1/0 sounds a bit large for a DC-DC charger. What is the Amps of the DC-DC charger? how far is the charger from the house battery? How far is the DC-DC charger from the starter battery.

Thank you. I’m so upset with Renogy, that I decided to go with a Redarc 40 amp DC charger. They recommend 4 gauge for a 16-30 foot run. I have a 20‘ run from my starter battery to the house batteries (3-105AH LiFePO4). Does this sound like it’s an appropriate size for this application?

That is so cool, thank you.