Flashlight Batteries From Laptop Battery





Introduction: Flashlight Batteries From Laptop Battery

Use the cells from an old laptop battery to power a flashlight

Step 1: The Flashlight Battery

Step 2: The Old Laptop Battery

The old laptop battery. Open the plastic cover and remove the cells

Step 3: Cut the Cells

Cut the cells with wire-cutter

Step 4: Voltage Testing

Test the voltage of the cells and use them from the laptop battery to the flashlight. It works very well for me!



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    Hi, Thank your for sharing this Instructable, the batteries you desire are 18650 Lithium Ion cells. Their Voltage is supposed to be 3.7 V with a capacity of ~ 3500 mAh.

    Please keep in mind, that these cells ( as long as they where recycled from another device ) are unprotected, that means that in a short circuit case, they will discharge with a huge energy amount. That can cause an explosion, please take care of yourself.


    Unprotected how? how would you protect them?

    The protection discussed is a battery over voltage and under voltage circuit. Example the 18650 batteries get their name from the diameter and length of the cell. The Battery is fully charged at 4.2VDC and fully discharged at around 3.2VDC this is the safe operating range for lithium power cells. LiPo, LiFe, Li-Ion.

    Most devices that use this type of cell has a protection circuit built into either the larger battery pack or the charger. Laptops this is in the pack. R/C stuff the circuits are usually in the charger/balance charger (over voltage) and Electronic speed controller (under voltage).

    There are individual cells that are protected that are used in things such as Vape power supplies and flashlight/torches and they can be Identified as they are longer then 650MM due to the protection circuit disk being sandwiched on before the shrink wrap. Those however are not the types in laptop batteries.

    That circuit does 2 things, Limits the charge going in so that the battery never goes over 4.2v (over volt) and it prevents it from going below 3.0V (under volt) As like others have said a Lithium battery that goes above or below can have negative results (POOOOOF FLAME ON)

    Thanks for that explanation, very well said.

    how to protect your batteries? rub some lithium grease all over your body and pray to the heavens while counting backwards 7 times. some say this doesn't work, but I say try it and post your results back here.

    with an inline fuse :)

    No, a fuse does nothing to protect from the two most common problems which are overcharge and over-discharge.

    They have a fuse build in, ~ 2 Amps

    you can buy a small circuit on ebay that does this