Cell level fuse: Different awg wire on positive and negative?

[BenjAZ]

Yesterday I watched a video of a youtuber called Average Joe testing some different things on his home made powerwall. One of those with 100-200 savaged cells with busbar and cell level fuse. He said one thing I'd like to understand, he was using 24awg nickel coated copper wire from the negative of each cell to the busbar. Ok till here, but he said that 24awg would be "way too thick" for the positive of the cells?? Why is that?

Is it because of the energy needed to weld that wire? or would it be related to the overcurrent protection once using the battery?

I'm intrigued...

Arround 9:30 of this video:
https://www.youtube.com/watch?v=qtZa941WhWo

 

[takyka]

Because you should not think about 24AWG as fuse wire for low current cell. It would melt only over 30A I guess.
In the video he was using glass fuses on positive terminal for overcurrent protection purposes...

T.

 

[BenjAZ]

Because you should not think about 24AWG as fuse wire for low current cell. It would melt only over 30A I guess.
In the video he was using glass fuses on positive terminal for overcurrent protection purposes...

T.

I know, so it's not necessary to use different gauge wire on positive and negative side on our batteries, is it?

 

[john61ct]

No.

Some use wires AS the circuit protection, poor man jury rig fusible link.

But with proper CP sized well below the wire rating, only downsides for heavier gauge wiring in general afaik is cost and maybe install difficulty.

And yes pos/neg sides of the circuit are usually same type size length wire, but within reason should not be a critical factor.

Except within the intra-connections of a bank's component batteries.

 

[john61ct]

And generally I find YouTube is a poor source of authoritative information

 

[spinningmagnets]

The actual fuse would be attached to the positive, since it always runs warmer than the negative of an 18650 cell.

The reason to use soldered wire on the negative, is because a wire can be soldered with much less heat than a wide ribbon, and you should avoid applying any heat to the center of the negative end.

As long as the negative connection is fatter than the positive (regardless of the type), the fuse-wire on the positive will continue to be the bottleneck to current, which is how it should be.

 

[spinningmagnets]

Be aware that "AveRage Joe" draws 1A per cell or less. He builds huge P-groups for a home powerwall, sometimes as many as 88P, etc.

The amperage of his fuse wires are WAY lower than what anyone would use for an ebike...

 

[BenjAZ]

I'm about to make my first battery pack with cell level fuse (already built 5 with nickel strips). Always spot welding. And you just confirmed what I thought.

Thanks guys!