DIY Lithium Battery and Car Conversion, page-3

Ouch, you need to know what you are doing here, unlike the old NiCd, NiMH and other chemistries all Lithium batteries can and do become unstable when over charged. They enter thermal runaway and that's exactly what anyone near should do because they become an explosive device and don't throw them in a bucket of water to cool off either, that makes the problem worse.

All consumer LiIon batteries are packaged with microprocessor control circuitry to stop overcharging and discharging which not only makes them vastly safer but lengthens their working life. There is nothing like that in the Vruzend DIY Battery Kit (although it is available separately) so it is up to the user to ensure the proper charging and discharging parameters remembering that any miscalculations could be lethal.