The Nitecore NL1840 is a powerful 18650 lithium-ion battery with a capacity of 4000 milliampere-hours (mAh) and a voltage of 3.6 volts. This rechargeable battery provides a reliable power source for a variety of devices that require high performance. Weighing only 50 grams, the NL1840 is lightweight and portable, making it ideal for use in handheld devices. The UN number 3480 indicates that this battery complies with international transport regulations for lithium batteries. The Nitecore NL1840 is an excellent choice for users who value a long-lasting and powerful energy source. It is particularly suitable for applications in flashlights, e-cigarettes, and other electronic devices that require a constant and reliable power supply. With its high capacity and the ability to be recharged multiple times, the NL1840 represents an eco-friendly and economical solution.