I have some fuses coming for the balancer leads, but not for each of the cells. Had to refresh my knowledge regarding failure current and breaking current. I've selected devices suitable for 300A breaking current and 10A failure.
The cell which 'exploded' due to a screw being misguided when I fixed the side plate, gave a noticeable pop when it let out it's electrolyte and a lot of heat. Then I was glad of the sideplates ! Needed to wash off the electrolyte because it's condictive, I think to the point that it could cause alopng duration leakage problems
The important thing was that it failed open circuit, more or less, and when removed it had a standing voltage of 0.8V. The neighbouring cells did not continue to pump current into it and cause the feared runaway condition, so a massive failure of a single cell is readily contained within the physical structure of these packs and doesn't seem to propogate to any neighbouring cells.
I guess this is the benefit of using such low capacity individual cells, the whole pack inherits an element of safety which a pack made oup of larger cells loses, due to it's the greater ability of a single cell to dump, and absorb current.
I think a fuse on each cell is a good idea if you are making a product for general purchase, to the 'I don't wanna have to do anything but drive it' section of the market, due to their litigious deftness
Showing due diligence in every possible way reduces the potential for success of a 'they should've expected and planned for that kind of failure' type of claim.
I did connect an 11A resettable fuse across one pack. It's thick connecting lead vapourised immediately....which reminded me to rate my fuses for a suitable breaking current !