As with all Nitecore batteries, safety comes first a range of safety features to protect you, your devices and charging electronics in use.

NL2140 4000mAh 3.6V - 3.7V Li-Ion battery with built-in protection electronics.

The 21700 battery features an innovative anode design with high temperature resistance, an integrated PTC to prevent high current surges, a pressure relief valve that activates when the temperature rises rapidly, and microporous membranes that protect the sensitive internal components. Built-in pressure relief valve, high temperature resistant design and built-in safety measures (BMS) protect the Nitecore batteries from overcharging, over-discharging as well as short circuits. 

Safe and robust 21700 cell for demanding users.

The NL2140 is made of high quality materials such as nickel-plated stainless steel connectors for impact resistance, good conductivity and oxidation resistance. The NL2140 is safe and reliable, insured worldwide and has multiple certifications for electronic use.

Safety instructions:

Please note that lithium cells may only be used by competent persons.
Incorrect handling or short-circuiting may result in fire or explosion.

Further properties:

Lithium-ion batteries are thermally stable and are not subject to memory effect.
They work on the basis of lithium and are characterised by a high energy density.

Notes:

A special charger is required for charging lithium ion batteries, which charges the batteries according to a special charging procedure. (CCCV = constant current, constant voltage.) The batteries must not be charged above a voltage of 4.2 volts, otherwise there is a risk of fire and explosion. It is advantageous to charge the batteries only up to approx. 4.1 volts, as this significantly increases the service life or the number of charging cycles (possibly up to double). Only lithium ion chargers may be used for charging. However, the cheap chargers sometimes have the disadvantage that they do not switch off safely at the end of the charging process, but continue to charge the batteries with a small charging current, which can be dangerous.

Furthermore, rechargeable batteries and batteries do not belong in household waste! Please dispose of them as prescribed by law at the municipal collection points or in the [usually green] containers provided by retailers.