Update 9/29/2019: 

Buying 18650 cells on ebay is tricky. Many weigh only 22 grams and are no where near what they claim the rated ampere * hours is.  I replaced the cells in a cordless screwdriver and found that the torque was not as good as original cells.  This is likely due to current supplied being low as torque in an electric motor is proportional to currect flow through the motor.

Research Links

 


18650 standard laptop lithium ion battery cell  

Dimensions in inches:  2.56 x 0.315 inches.  Wikipedia: List of Battery Sizes

The 18650 lithium cell battery can be purchased for on the order of 1 dollar per cell on ebay.  This makes it very attractive for fixes to devices whose battery packs have died.  Also of interest is the fact that since the lithium cell voltage is 3.7 volts less cells are required to replace a NiCad pack. This means that in many cases there will be sufficient space for the lithium cells to fit in the old battery pack.

Research Links

Battery Protection and Balance Circuit

 

  How To Convert / Replace Ni-Cd To Lithium by using 18650 cells li-ion

Categories: Engineering

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