The vaping industry uses Lithium-Ion batteries due to their safety and reliability record. In recent years the critical failure rate of quality Lithium-Ion batteries has dropped to 1 in 10Million.

When these batteries fail it’s usually the fault of mishandling. There are some simple safety precautions you can take to ensure the best performance for your batteries.

General Best Practices

Do not use the battery if:

-It has rust or corrosion on it
-If the wrap has been damaged even if it’s a small nick
-The wrap is peeling off
-It is bulging
-It is giving off an odor
-It feels hot to the touch
-Anything doesn’t look, smell, or seem right

When in doubt, most Vape shops can re-wrap your battery for cheap/free.
If you aren't near one, or can't travel, I'd recommend getting in contact with a member who knows their stuff and can inform you on re-wraps.

Keep the battery and all other vaping supplies away from children and pets.

Never store your batteries in a car or in direct sunlight. 70F degrees can quickly reach temperatures over 100F degrees in a car. Even if it’s “just for a moment” don’t do it.

Charge new batteries before using them.

If you’re using a mod that uses more than one battery, those batteries should be the same age. You should "marry" the batteries to each other: buy them together, use them together, charge them together.

If the battery becomes hot inside your mod, remove it from the mod and discontinue use.

When carrying spare batteries with you, make sure you’re carrying them in such a way that nothing metal (keys, pens, etc) can connect to both poles of the battery or damage the wrap around the battery. Accidentally closing the circuit like this can cause the battery to rapidly discharge and short out.

Charging and Use

The best way to charge the 18650 batteries for your mod is with an external 18650 battery charger.

Allow the battery to rest for 10 minutes after charging and 30 minutes before re-charging.

Never charge a battery unattended.

Temperature Concerns

Lithium-Ion batteries don’t like extreme temperatures. Heat and cold stress the batteries. Charge and use the battery at room temperature. If you’re uncomfortable, your battery is uncomfortable. If the battery has been exposed to extreme temperatures, allow the battery to return to room temperature before charging it or using it.

I recommend not using a battery if it has been exposed to temperatures over 140F.

If you’re storing a battery long term (months or years), discharge it to 3.8 volts and store it in a cool dry place. A refrigerator works well for this, but you need to protect the battery from moisture.

Ensuring Longevity

Modern quality Lithium-Ion batteries do not have the memory issues that older rechargeable batteries had. “Topping off” your battery is better for it than allowing it to completely discharge before recharging it.

After a few charge cycles, your battery will be “broken in” and you’ll get the full benefit of the mAh.

A typical Lithium-Ion battery is good for about 500 charge cycles. The overall lifespan of the battery is dependent upon how frequently you charge the battery. As the battery ages the life span of a single charge will shorten and the battery should be replaced.

Notice: I lifted this and edited it from support.johnsoncreeksmokejuice.com/hc/en-us/articles/204913734-18650-Battery-Safety-and-Best-Practices.