Unprotected IMR cells for Flashlights?

Hi there,

I have two 18650 flashlights, they using a single 18650 protected 3A battery, and using a XM-L2 led about 900 and 1100 lumen.
can I replace a protected pin-top 3A 18650 2600mAh battery with an unprotected flat-top 20A 18650 2100mAh battery? (but this unprotected flat-top cells claim that it will cut off at 3.0v, is it protected?)

Is it safe if I use the 20A IMR battery for my flashlight?

You don’t know what they sold you.
They don’t know what they sold you.

It depends on whether the driver (the little electronics board that sits between the battery and the LED) has a feature that will either

  1. shut off power when the battery voltage drops to some specific voltage, or
  2. at least, make the light blink to warn you

AND, protection by detecting the battery voltage assumes some typical battery.
A relatively low drain battery can work for a long time before its voltage drops down to whatever the cutoff is set to be, by which time the battery is truly drained rather far.
A relatively high drain battery allows pulling more power out faster — and the voltage may drop while in use (and hit cutoff) but recover, if you check with a voltmeter.

Every “protection” circuit is a specific electronics design and — if they were made right — behaves in a predictable way. But they don’t all behave the same way.

Do you know the precautions to take using lithium-ion batteries?
In particular, do you know why it’s important not to inhale, if something leaks out of the battery?