If your device has an internal battery, charge it with the charger provided (a USB cable is not a charger, it is just the cable to plug it into a charger). If it doesn't come with a charger, please ensure you don't charge it with more than 1 amp and 5 volts. Charging it with more than this can damage or destroy the battery. Cell phone chargers or car USB chargers often provide more power than this. Computer USB ports can vary in how much charge they deliver please make sure you use a port that supplies a safe amount of power for recharging vaping devices. Do not use USB3.0 or 3.1 for charging as these ports can provide more than 1 amp of current, you can recognise these ports by the blue coloured plastic on the inside of the port.
Charge your device fully when charging it and even if your device supports "pass through" use (able to use it while it's charging) we recommend you don't as it can reduce your devices battery life span.
If your device uses external batteries, commonly 18650 Lithium-ion batteries, you'll want to use an external charger even if you can charge them with your mod. There's not the same overcharge protections with onboard charging as there are with an external charger. In fact, most manufacturers recommend you use an external charger.
18650 Li-ion batteries are high discharge batteries; they can provide an incredible amount of current in a very short period of time. As such you need to be very careful with them. Never put loose 18650 batteries in your pocket or bag - if they short out on your keys or loose change they can vent, releasing burning hot/flammable gas/liquid. We recommend that you put your spare 18650s in a battery case.
If your device uses multiple 18650 batteries we strongly recommend using only married batteries in it. Married batteries are the same type of battery, which were bought at the same time, from the same batch which have always been discharged and charged together. If you use unmarried batteries in a multiple battery device you risk either damaging the device or venting the batteries.