here is the link to a calculator , which give you Dc Resistance of your nickel strip or cooper wire

https://chemandy.com/calculators/rectangular-conductor-resistance-calculator.htm

with the Dc Resistance and U=Ri and P=Ri2 you got your voltage drop, heat of battery

don’t forget to X by the numbers of connection on your battery

i was suprised by the number: a classic nickel strip 7mm x.15 in cross section (for amp) so around 20mm long has a Dc Resistance of 0.0013 so

at 10A / cell : 0.013v drop and 0.13W of heat, it looks over killed

copper 4.33 times better but the busbar is 12-14 times longer and has 12-14 times the amp

so my question is (since we cannot real refer the usual nickel strip values , and some urban legend)

what is a acceptable value of total W of heat for a efoil battery or bus bar?

aiming for 0.3v/cell drop max ?

edit:

after some calculations : on 12s12p if i want to put the same heat of the nickel strips on the busbar i should be fine with 4x 1.5mm2 rigid copper wires… (?) something like 40w for 120A