@scrapheap Thanks, I’ve carefully read through that thread. But my concern still remains.
For my first build, I was thinking a lot about using a fuse on main battery terminals, but after I read that @Jinra had an accident because of a blown fuse, I decided not to use it:
Cell level fusing looks like a safer option because one blown fuse does not mean that your esk8 shuts of. But it may not be that much safer in this respect.
As many people wrote here, fuse wires often come loose (because of vibrations, bad soldering, etc.) If one or more fuses wires come loose, you many not immediately detect it unless you balance charge your board every time. (And even if you check balance every time, you can detect it only when you charge.) The cells will become unbalanced, and I am not sure that a BMS can help with this.
So the battery pack may be compromised, but the rider will be totally unaware about this.
Say, in a 4P setup, if one or two fuse wires in the same block are disconnected, then this P block is effectively 3P or 2P. If the rider puts it under stress (hard acceleration, going uphill for a long time, or both at the same time, etc.) it may easily reach the breaking point, where it was working fine last time. If this fuse blows, this immediately makes the current through the remaining fuses in that P block (which are already close to blowing) 2 or even 4 times higher than they should be. I am pretty sure that these fuses will immediately evaporate. So the board will shut off at the moment when the rider least needs it.
Tesla uses cell level fusing, but they have huge number of cells in P blocks. If a few fuses blow, it will not have a big effect on currents through remaining fuses. For esk8, where people typically use 3P or 4P setups, cell level fusing is more questionable.
I am not trying to say that it is bad. I am actually trying to figure out if and how to do it in a safe way for my next build. But there are lots of questions here.
With commercially available fuses, we know exactly when they are supposed to blow. With fuse wires we can only guess it. There are so many parameters here, not only the gauge of wires, but only the length, the amount of space and ventilation around them, heat dissipation, etc. Basically, there is no way to figure out the blowing amperage, unless one does a thorough testing of a given battery design under various conditions. Apparently @chaka does it for his packs. But I am not sure that I can do it (or even have means to do it).
If the amperage is too low than the battery is not safe (can shut of easily), if it is too high than cell level fusing defeats its purpose.
