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21700
A 21700 battery is a rechargeable lithium-ion cell that measures about 21 mm across and 70 mm long, which is where the name comes from. It is a step up in size from the 18650, so it holds more energy in one cell and runs a power-hungry optic or IR light longer between charges.
Right now this category carries the PARD 21700 Li-Ion Battery, a spare for PARD devices that take a 21700. Keep one charged in your pack so a dead battery doesn't end the night just as the coyotes start moving.
21700 vs 18650
The two look alike, but they won't swap. A 21700 is wider and longer, so it won't fit a device built for an 18650, and an 18650 will sit loose in a 21700 compartment. Match the cell to what your optic or light calls for, and check whether it needs a button top or flat top and whether it wants protected 21700 cells.
For charging, use a 21700 battery charger with bays long enough for 70 mm cells. Cold drains lithium cells faster, so carry spares in an inside pocket on winter hunts. If you'd rather add runtime with a rail-mounted pack, browse our external battery packs. Batteries can't be returned, so double-check the size before you order.
Frequently Asked Questions
Is 21700 better than 18650?
For capacity, usually yes. The 21700 is a larger cell, so it typically stores more energy and handles higher current than an 18650. Better only counts if it fits, though. Your optic or light is built around one size, and the two cells are not interchangeable.
What is the average lifespan of a 21700 battery?
A quality 21700 generally lasts several hundred full charge cycles before its capacity drops off noticeably. How you treat it matters. Avoid running it completely flat, don't leave it in a hot truck, and store it around half charged during the off-season to keep it healthy longer.
What is the lowest voltage a 21700 battery can reach?
Most lithium-ion 21700 cells shouldn't go much below about 2.5 to 3.0 volts. Draining past that can damage the cell for good. Protected cells and most optics shut off before you get there, but a battery left dead for months can creep lower, so recharge it soon after a hunt.
What are 21700 batteries commonly used for?
They show up in high-drain gear: flashlights, IR illuminators, hunting lights, power tools, electric vehicles and some thermal and night vision optics. Hunters mostly run them in IR lights and in optics that need long runtime, such as PARD units that take the PARD 21700 Li-Ion Battery.
Can I charge a 21700 with an 18650 charger?
Only if the charger's bays are long enough for a 70 mm cell and it supports lithium-ion chemistry. Many newer chargers handle both sizes, but older 18650-only units won't hold a 21700. Check the charger's listed sizes before you try, and never force a cell into a bay.
