Is dangerous to use lipo or li-ion battery for nichrome wire heating?

If you use it directly with no BMS and for a long time, you could over discharge the battery and it will never fully charge back. Better use a BMS bewteen battery and wire.

If you are experimenting then use polyfuses to limit the current to the C rating and use a low voltage cutoff to avoid over discharging the battery. Mistreated lipo or li-ion cells have a tendency to catch fire.
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