What can I use as fuses between parallel 18650 cells?

[Offroader]

I'm building a 18650 pack, and each two cells will be in parallel.

I need to put the other 14 cells in parallel for balancing. I was thinking, I might as well use some kind of fuse between the cells just in case of a short I will only be shorting 2 cells, instead of all 14.

My question is what can I put between the cells to fuse them?

Do I need to use fuses, or can I weld in a 2mm wide strip of think nickel?

The other question is if you recommend a fuse, what type of use and what amp rating should I use?

Thanks.

In the picture you can see that each two cells are in parallel and a wire is used to connect in series, the cells are not all in parallel. What would you recommend?

 

[fellow]

Fuse or strip/fuselink, it does not matter as long as You have the correct conductive fuse area. To calculate it for Ni, see Cu fuse area values bellow and derate it accordingly.

I see that your cells are of different type (mixed red and green), this is not recommended att all.

Recommended main fuse for 2P ebike configuration(10A continous capable cells X 2, 18A peak per cell X 2): Littlefuse 0326015.MXP 15A, 6.3mmx32mm antisurge ceramic. Its data: V_max=125VDC, slow blow, 15A=4h continuous, 20A=1h continuous, 30A=5 to 60 seconds. Main fuse is calculated (and tested IRL) to blow before the fuselinks.

Fuselink between the cells: A=0.75mm^2 silicone copper wire. This blows if the main fuse fails. Means that something is seriously wrong, not a normal short!

Main wire: A=1.5mm^2 silicone copper wire. This blows last. If this blows, than you screwed something really really big time.

If 20A cont capable cells (x 2), double everything (i.e. 30A main fuse, 1.5mm^2 fuselinks, 3mm^2 main wire). All wire/strip areas are for Cu. Recalculate those values for other materials than Cu.

Silicone wire=fuselinks
Normal ABS plastic wire or similar=fireworks

It is easy to check if the fuselink wire area is too small. Hold it in your hand, it should not get hot during normal peak power use (you can make a test wire and route it temporary to the handlebars).

 

[999zip999]

The only reason you would build a pack like that if they came that way. like a high quality tool pack. High quality cells are needed to get away with that design. Get good quality cells and put them in a large parallel for your needs. Better for high amp needs of an ebike.