Lithium ion batteries are known to be safe, yet it can in extreme cases, typically by shorting the battery to prevent gases (8 bar pressure explodes)
The Yihi fuse works as a mechanical fuse in your (mech) mod and detects short circuits. If the Yihi fuse is activated by a short circuit, then it is no longer usable.
Protects against short-circuit in MODS with one or two batteries with up to 7.4V.
Protects the battery during charging
Protects VV mods, etc. that have a build-in chipboard.
If the Yihi Fuse is activated by closing you can not use your mod and should be replaced Fuse