If you own a modern tactical or EDC flashlight, there is a good chance it runs on an 18650 battery. These rechargeable lithium-ion cells pack a lot of energy into a small package, which is why they power everything from flashlights to headlamps to power banks.
What the name means
The number is the size: 18 mm in diameter and 65.0 mm long. It is a little bigger than a AA battery.
Voltage
18650s are nominally rated around 3.6 to 3.7 volts and are fully charged around 4.2 volts. That is much higher than a 1.5 volt AA, so never mix them up or drop one into a device that is not designed for it.
Capacity: what mAh tells you
Milliamp-hours (mAh) measure how much energy the cell stores. More mAh generally means longer runtime.
- 2600mAh: a solid, lighter everyday cell with good runtime.
- 3200mAh: more capacity for longer runtimes in high-output lights.
Be skeptical of cells claiming 5000mAh or more. The chemistry does not support it, and those cells are usually fake.
High discharge
Very bright lights pull a lot of current. A high-discharge cell is built to deliver that current without overheating or sagging. If your light is rated at 2,000+ lumens, use the cell the manufacturer recommends.
Protected vs. unprotected
A protected 18650 has a small circuit board built in that cuts power if the cell is over-charged, over-discharged or shorted. For flashlights and everyday carry, protected cells are the safer choice. They are slightly longer, so check that your light accepts them.
Button top vs. flat top
A button top has a raised positive terminal. Many flashlights require it to make contact. Check your light's manual.
Charging tips
- Use a charger made for lithium-ion cells.
- Do not charge unattended on flammable surfaces.
- Stop using any cell with a torn wrap, dents or swelling.
Carrying spares safely
Never carry loose 18650s in a pocket with keys or coins. Metal can short the terminals and cause the cell to overheat. Use a plastic battery case, then keep the case in a sealed pouch so it stays dry. A waterproof admin pouch is ideal for spares, chargers and cables.
Storage
For long-term storage, keep cells partially charged in a cool, dry place. Check them every few months.
Our cells
We carry Powertac protected 18650s built for their tactical lights: the 2600mAh and the 3200mAh high-discharge cell. They pair with the E9R GEN4 flashlight. See our EDC flashlight guide for more.
FAQ
Can I fly with 18650 batteries?
Spare lithium-ion batteries generally must go in carry-on, not checked bags, with terminals protected. Check your airline's rules.
How long do 18650s last?
A quality cell typically lasts hundreds of charge cycles. Replace it when runtime drops noticeably.
