Foursevens 16650 (2200mAh) Rechargeable Li-Ion The safer alternative to 2x(R)CR123 cells WORKS WITH: Foursevens Quark QK16L 16650 and other legacy Quark Click/Pro/Tactical (also other 4.2V two cell lights). Does NOT work with the Quark Smart. If you have questions about whether a 4.2V Li-Ion battery will power a light that is NOT a Foursevens light you should contact the manufacturer. Theoretical Run Time Comparison @ 1A: Foursevens 16650 2200mAh = 3 hours 2xRCR123 750mAh = 2 hours (poor capacity & explosion risk) 2xCR123 1500mAh = 3 hours (good capacity but explosion risk) This rechargeable 16650 battery has capacity equal to 2xCR123 cells and significantly more capacity than 2xRCR123 cells. The upcoming Quark QK2L 16650 will ship with this battery included, but we highly recommend using this battery in all of your two cell lights that are compatible with 4.2V. Why? Because we believe that running a light with 2x(R)CR123 is dangerous. Using two cells in series creates a significant chance of catastrophic failure if the batteries become imbalanced. Imbalance can be caused by batteries of different age, manufacturing defect, or difference in charge state. For example, you accidentally put in a charged battery with a discharged battery. This imbalance can lead to fire or explosion in one of the cells. This is not uncommon. Even if you think you are diligent, why take the risk when a much better option is available? This is also why we are no longer shipping any Foursevens lights with 2xCR123 cells. PROTECTION CIRCUIT: These batteries contain a specialized electronic "protection circuit" for user safety. The prevents over charge, over discharge, over voltage, and under voltage conditions. RECHARGE EARLY AND OFTEN! Do not run these batteries until they are completely empty (when the light shuts off on its own). Doing so will trip the protection circuit and render the battery inoperable. The Foursevens Flex Charger and Xtar VC2/VC4 chargers are normally able to reactivate a tripped battery; however, this is not best practice and fully draining the battery causes long term damage to the cell. PLEASE NOTE: Exceeding the maximum voltage of your flashlight can cause permanent damage to the flashlight. Before using these batteries please ensure that your flashlight is rated for up to 4.2V. This battery is rated to 4.35V and 2500mAh, but most chargers only charge to 4.2V and that's why we have rated the battery at 2200mAH.
