Question about wiring batteries to bus bar

[whereitsat42]

Hi there, had two quick questions I was hoping someone would be able to help me out with (I checked the docs linked in the forum and didn't see a clear answer to these):

1)Do the wires I connect my batteries to a bus bar with need to support the combined input from the panels and output to the load, or just whichever is the higher of the two? In other words, if my panels produce max 40 amps and my load is a max of 20 amps, do I wire for 40 or 60?

2)Does the wiring for each battery need to support whatever the answer to #1 is, or can I get away with dividing that number by the number of batteries? So if the answer to #1 is 60 and I have 6 batteries, can I wire each battery to handle 10 amps, or does the wiring connecting each battery to the bus bar need to support the full 60 amps?

Thanks to anyone who can help, you guys have been really helpful in helping me get oriented and I appreciate you all taking the time to share your expertise!

Stu

 

[12VoltInstalls]

just whichever is the higher of the two

Maybe-

my panels produce max 40 amps and my load is a max of 20 amps, do I wire for 40 or 60?

40A is the literal answer to your question.
However, I would probably just use 2ga battery cables. Are you going to use an inverter? Than you size for that.
I oversize cables at least 2x and fuse for the load but that’s not a requirement- just what I do.

In my situation I have three 100A output capacity batteries connected with ~150A cable and 125A fuses to the busbar. The inverter is 2000W or ~170A at 12V nominal. I use 2/0 cable (~200A) and 200A fuse (might actually only be 150A fuse?)

The fuse is supposed to protect the wire(cable) and I generally fuse at or above the max expected load so it blows if there’s an issue even though the cable is capable of more. None ever have blown.