How to do correct test and determine whether a 18650 Li-ion is protected or non-protected battery?

  • 1
    \$\begingroup\$ Check the datasheet? \$\endgroup\$
    – winny
    May 11, 2021 at 7:01
  • \$\begingroup\$ If it has a consumer label it is probably protected. If it doesn't, it is probably not. Samsung does not sell protected cells. Other companies may buy samsung cells and add protection, but they will also put their log on the cell. Same goes for Sony, Panasonic, etc. They don't cell protected cells. \$\endgroup\$
    – user57037
    May 11, 2021 at 7:37

1 Answer 1


A protected LiIon battery will disconnect the output of the battery to prevent overdischarge. It also has overload protection. You could do one of the following:

  • Discharge the battery using a resistor. If the battery voltage drops below 2.3V, then the battery is not protected.
  • This test is only for the bold: Connect a slow blow fuse, e.g. 500mA directly in parallel with the battery. If the fuse survives, then the battery is protected, because the protection circuit should protect the battery from short circuits.

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