i've seen a few Videos now, where people use fuse wire as single cell protection layer for parallel battery packs to protect against catastrophic failure due short circuit of a defective cell.

Often these battery packs are sealed with heat shrink tube resulting in these fuse wires to be (more or less) air tightly sealed.

Is that safe? Will those trigger even without air? My understanding is, that fuse wires will act as a circuit breaker by simply burning through, which seems difficult without air?

Thanks for your time.

  • \$\begingroup\$ If you DIY a fuse, though, you may not satisfy local codes. It may be worth using a fuse that is rated/listed by safety agencies such as UL or similar. \$\endgroup\$ – mkeith Jun 18 at 7:44
  • \$\begingroup\$ If it's a bare fuse wire that is totally surrounded by heat shrink tubing then it's not going to be effective because when it melts, the melted parts cannot escape and potentially remain in electrical contact with each other. \$\endgroup\$ – Andy aka Jun 18 at 9:19

Absence of air is good for a fuse. The fuse opens by melting. Air, and especially the contaminants in it in industrial regions, can sometimes degrade a warm fuse wire over time.

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  • \$\begingroup\$ What about the second comment to the question? What if the melted wire cant escape because of the heat shrink tube? \$\endgroup\$ – Xardestro Jun 18 at 13:23
  • \$\begingroup\$ @Xardestro might be true if the tube was ceramic, A soft plastic tube containing molten copper? I think not. \$\endgroup\$ – Neil_UK Jun 18 at 14:31

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