Correctly sizing Fuses for Battery pack discharge leads?

[Gorillazilla]

Ah, so the fuses in your car are the protect the battery, and the ones in your house protect the electric companay? I didn't realize people used fuses to protect the source except within the source device, but that's an interesting concept.

The fuse is kind of within the device being protected, the output leads are a part of the battery. Though, could move the fuse inside the battery casing, and into the wire between the BMS and the cells. Might be a bit more of a pain to replace the fuse, but would only be needed when the controller shorts out....

As for the fuse protecting the electric company, in this case Just think of it like the electric companies powerplant is a pygmy volcano in your garden that may erupt if you try to pull too much power from it

 

[dominik h]

Sorry, just reread the spec sheet.
Had the wrong number in mind. Blame on me.
It's 1.2mOhm per cell.
Cenat CPB-LM20
Had also a few bigger cells (60Ah) but not enough for a build and had their numbers in mind.

 

[dominik h]

The controller was repairable after that!?
So the fuse cut off the power before enough went into the board to burn it.

The controller was running again for a few days, since there it does not recognize the hall sensor position anymore.

 

[E-HP]

Ah, so the fuses in your car are the protect the battery, and the ones in your house protect the electric companay? I didn't realize people used fuses to protect the source except within the source device, but that's an interesting concept.

The fuse is kind of within the device being protected, the output leads are a part of the battery. Though, could move the fuse inside the battery casing, and into the wire between the BMS and the cells. Might be a bit more of a pain to replace the fuse, but would only be needed when the controller shorts out....

As for the fuse protecting the electric company, in this case Just think of it like the electric companies powerplant is a pygmy volcano in your garden that may erupt if you try to pull too much power from it

Unfortunately, I beleive the best way to protect the battery pack, and the rest of the cells, is will cell level fusing, like the fancy packs use, but even that would require the pack to be reparied afterwards.

 

[Gorillazilla]

Unfortunately, I beleive the best way to protect the battery pack, and the rest of the cells, is will cell level fusing, like the fancy packs use, but even that would require the pack to be reparied afterwards.

Nah, cell level fusing like on the EM3ev battery packs just helps reduce the severity of a cell internal short event, really rare. Besides, the cells themselves have a kind of internal fuse mechanism in the form of the PID

A fuse on the output lead is sufficient to protect the battery from a shorted Speed controller.

 

[Gorillazilla]

Just an update, went with a middle ground. https://www.ebay.co.uk/itm/313160298270 80A fuse, so should blow well under a second at 400A I think the 7 cells in parallel rated at 70A continuous can just about handle that for such a short time without damage.