Resurrecting this thread after my recent hishap. I want to be extra cautious with my next battery pack. I’m considering the NESE modules to minimize the risk of abrasion damage and using fuses to minimize the risk of a short. (I believe the combination of these two must have been the root cause of the fire.)
The NESE modules use these bars for making serial connections:
The shape is very similar to a MIDI fuse:
The holes are M5 in both cases. The hole distance on the fuse is 30mm and 23mm on the bus bar. Not a perfect match but close enough. The fuses could still be used in place of the bus bars if some space between the NESE modules is allowed.
The idea is to use fuses for all serial connections in order to minimize the risk of a short circuit. It’s of course not bullet proof. A short across a single parallel group would still be possible. The effort here is not to prevent the possibility of a short completely but rather highly reduce the risk.
Questions:
Is this a good idea?
I can definitely see the risks of using fuses. Loosing brakes while going downhill because of a blown fuse is not fun. Still, I would rather take a spill than burn my house down. Also, braking currents are lower than discharge current so I believe a fuse is much more likely to blow when accelerating than when braking.
If thermal runaway is the main concern, would it be better to ditch the NESE and do cell level fusing instead? That should be close to bulletproof.
What fuse rating should one use?
Consider a 60A battery current limit on a VESC, 12S4P battery pack using Samsung 30Q cells, and 60A MIDI fuses (say these that are rated 58V).
Four parallel 30Q can deliver 60A continuous. I haven’t been able to find how much current they can discharge if short circuited. Will that be enough to blow the 60A fuse? According to the datasheet, the fuse will require at least 150A to blow within 1 second. With 120A or less, it will take at least 10 seconds for the fuse to blow, which is not helpful at all.
Does it only make sense to use a fuse if the batteries are able to discharge current that’s way above the configured battery current limit?