Specifically, 18650s are commonly used in vaping. A guy who goes by Mooch once tested a large number of 18650s he could find on the market - it turns out that a

Specifically, 18650s are commonly used in vaping. A guy who goes by Mooch once tested a large number of 18650s he could find on the market - it turns out that almost all off-brand batteries (everything other than Samsung/LG/Sony) do not live up to their stated maximum continuous power draw specifications, never mind fake ones. Vaping often draws power at reasonably close to the stated limits, and the failure mode of these batteries is venting toxic gas and potentially exploding. I assume there's similar issues with all large batteries. In a nutshell... fake batteries on Amazon can harm people badly.