No matter what type of device you prefer, if you're using rechargeable lithium ion batteries to power it (and you almost certainly are) - basic battery safety and handling techniques should be part of every day.
It doesn't take much effort to safely charge and transport batteries whereas the cost of just 'throwing a couple spares in your pocket' can be more than you want to pay.
For our part - we sell only high quality Li-ion batteries from reputable manufacturers. When we have concerns about a company's practices or processes - we stop selling their batteries.
We urge you to store your batteries safely - especially if you're carrying them on you. That means store them in such a way that the terminals (the 'ends') of the battery can not come into contact with metal objects; i.e. - loose change, pocket knives, money clips, your lucky hand grenade, etc.
Efest H2 Battery Case (18650) - $ Vape Wholesale to the Public