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Foursevens 18650


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    Shipping Warning

    Postal regulations do not permit shipping Lithium Ion batteries outside of the U.S. unless your order also contains a flashlight. If you are shipping outside the US please add a flashlight, or remove the Lithium Ion battery.

    Foursevens 18650
    Foursevens 18650 Foursevens 18650 Foursevens 18650 Foursevens 18650
    Product Overview

    FOURSEVENS 18650 (3400mAh) Rechargeable Li-Ion:
    WORKS WITH: Prometheus Alpha (and other 18650 lights that accept a protected cell)

    Product Details

    We finally made the leap and now have our own customized batteries! As you know, I'm obsessed with quality and these li-ion cells are top of class and are guaranteed to deliver.

    What you get for your money:

    Reliability: Less chance the cell stops working for no apparent reason (it happens)
    Consistency: Every battery has similar performance (as opposed to variable)
    Safety: Mechanical and electronic safety features (a "protected" cell)
    Lifetime: Longer total life span because of the characteristics above

    Recharge early and often!

    Do not run rechargeable 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, best practice is to recharge early and often. Fully discharging the battery causes long term damage to the cell.


    ALWAYS store batteries in a protective case that will prevent short circuits. NEVER put bare cells into a pocket, bag, or drawer. A short circuit will lead to an uncontrolled release of energy...otherwise known as a ball of molten lava.

    Do batteries have a "memory" effect I should worry about?
    NO. Modern rechargeable batteries (Li-Ion or NiMh) do not have any memory effect. It's best practice to recharge early and often. In fact, fully depleting a battery will damage it and reduce the overall capacity.
    what is the shelf life of a charged battery?
    Generally speaking, all our batteries will retain 80% of their charge after six months. People worry about this more than they should. Modern batteries hold a charge for a long time. Just charge them and put them away properly. You should charge batteries once a year. Putting them in the fridge is also a myth. Don't do it.
    Does heat or cold have a negative effect?
    Li-Ion and NiMh batteries can be operated in sub-freezing temperatures. However, a cold battery will deliver less capacity (run time) than expected. Batteries should ALWAYS be at room temperature before charging. Charging a frozen battery can permanently damage the cell and lead to an internal short circuit. In a Li-Ion battery this can cause a fire. Most batteries can tolerate heat up to about 104F/40C. You should never leave a light (or any device) inside a car and exposed to direct sunlight.
    Should I leave batteries on my charger all the time?
    NO. It's best practice to remove batteries from the charger once they are fully charged. It also depends on the quality of your charger, but again, best practice is to remove the batteries. Some low quality chargers can create a risk of fire.
    Can I install batteries backwards to prevent accidental activation?
    NO! Back in the day people would install batteries backwards in a light for storage and to prevent the light from turning on by accident. You should NEVER install batteries backwards in electronic devices.
    Protection Circuit
    These batteries contain a specialized electronic "protection circuit" for user safety. The prevents short circuit, over charge, over discharge, over voltage, and under voltage conditions. Li-Ion batteries contain a massive amount of energy and you don't want to mess around with that. A protection circuit is like the seatbelt in your car. You don't want to use it, but it's there if you need it. Some people think flashlights have built in features to prevent accidents, but this actually FALSE. Those features are meant to protect the light, not the battery or your person/property.
    We ALWAYS recommend the use of "protected" batteries, excluding special circumstances.
    impact resistant wrapper
    A special heavy-duty wrapper material resists cracking, unlike standard battery wrappers. This does make our batteries slightly thicker than comparable cells.
    Premium cells
    We use only top quality cells from reputable manufacturers. Obviously we recommend our own batteries because we can guarantee the quality, and our lights are designed specifically to work with these batteries. NEVER (ever) purchase Li-Ion batteries on eBay because of rampant counterfeiting and sub-standard quality. These batteries can be dangerous and lead to fire and/or explosion. Saving a few bucks isn't worth burning down your house with your family inside.
    • Size
      18650 (18.75mm x 69mm)
    • Weight
      1.8 Oz
    • Terminal Type
      "Button Top"
    • Voltage
      3.7V Nominal (4.2V full charge)
    • Capacity
      3400 mAh
    • Service Life
      ~500 Cycles
    • Charge Retention
      80% @ 6 Months
    • Maximum Discharge
      7 Amps @ 2C
    • Electronic/Mechanical Protection
      Over charge, over discharge, over voltage, under voltage, short circuit
    • Where it's made
    Customer Reviews
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