18650 protected batteries (with BMS) have an electronic circuit. The circuit is built inside the battery pack that avoid the battery from over charge, over heat, over discharge, over current and short circuit. battery with BMS is much safer than an 18650 unprotected battery (battery cell) less likely to overheat, fire or even burst.

18650 battery cell is cheaper, but we do not suggest. it shall only be used where the load and charge is externally monitored and controlled. it normally be called button top, but please check specifications.

If a battery pack is damaged or looks corroded or appears to be leaking, please get rid of it and send to recycle center.

how frequently do I charge the battery

The method you charge your battery affects lifespan of the battery. If you can measure it, try to release from 3.7v down it to about 3v before you recharge. If you are not sure, use a device until it claims the battery pack needs to be replaced. For example, a flashlight, run it till the light is dim or power off. A professional adapter/charger shall tell you the voltage so you can finally be aware of the lifespan in different devices. If you charge too frequently you may use up the lifespan.

Some people don't let the voltage drop below 3.3v (or even higher). different 18650 model has different maximum cycles. so this is really a process of matching the device and application to the lifespan of battery. Be aware that a 18650 battery pack that go down under 2.5v may "lock" the device so it could not be using. The "lock" occur in device such as electric cigarette.

how to know if the battery dead?

Battery loses charge much quicker than normal. generally after a few days or even worse the same day

Battery gets hot when charge or discharge, hotter than normal.

Battery be used over 3 years.

Battery hold less than 80% original capacity.

Charge time is unusually longer.

There is ANY crack or deformation in the battery.

Those are the 7 signs indicate that your battery pack is dead and it is time to get a new one. If you ignore the warnings you are risking fire or even explosion while using.

18650 chemistry

There are different chemical combinations for 18650 battery. We advise to focus on protected mode, the chemistry can change and isn't always reported. Here are main types currently. Depending on your device requirement, choose the most appropriate type.

LiMn2O4: Lithium manganese mixture

other name IMR or LMO or Li manganese

LiNiMnCoO2: Lithium manganese nickel

other name INR or NMC

LiNiCoO2: Lithium nickel cobalt mixture

other name NCO

LiCoO2: Lithium cobalt mixture

other name ICR or LCO or Li cobalt

LiFePO4: Lithium iron phosphate

other name IFR or LFP or Li phosphate

LiNiCoAlO2: Lithium nickel cobalt aluminum mixture

other name NCA or Li aluminum