I am using threshold of 2V and below because some cells will go down to 2V no problem.
The point is - do not make experiments with li-ion cells unless you have ready and operable >> Foam extinguisher, CO2, ABC dry chemical, powdered graphite, copper powder or soda (sodium carbonate).
Take a look at new LG 18650 batteries and warning printed on them (NO more bare li-ion batteries for us).
Actually its worse, don’t do this unless you have a fireproof automated system that monitors your batteries 24/7 and can automatically extinguish flames with lithium fire fighting powders (water is ineffective on lithium fires i believe).
Also you need to prevent explosions from reaching a human if it explodes while in use (build flashlights from 3 inch thick aluminum with pressure vents that filter hazardous fumes, not likely.
Before I decked it out with an automated fireproofing system, I would put them in the garage with a bag of play sand above them. If a fire starts, the heat or flames burst the plastic and bury the cells in play sand.
