The 'target voltage' used can definitely effect lifespan. Generally, if you stop 10% shorter, you DOUBLE the useful life (measured in 'cycles'). But you have 10% less 'minutes per charge'. The urge, quite naturally, is for makers to push it as far as they can. Big numbers (in terms of run time) mean bigger sales? For normal Li-ion cells this is 'set' at the 300 cycles point almost universally (the military often specifies lower points (3.95 not 4.2 typically), so you have to recharge a bit more often, but field replacement of battery packs is eliminated).
Cell phone makers are really driven here, they want every minute they can get, hopefully vape makers not so much?
While longer life can be had by 'stopping early', a well designed charger circuit should protect the cell it's supporting against leaving it on too long. The line it fine, especially with LiPO, so being 'just a little high' on any individual unit (a flaw), could well be fatal.
For the reasons in the BU articles above, it should be safe (but perhaps not advised) to leave them on charge.
Regards to all.
OF
