Not a good day for 2*18650 lights...

So this morning, my modded Roche LS01 stopped working after I was cycling through some modes. I’m thinking it might be the switch since I’ve had them go out on me before….

And just now, my un-modded Trustfire 500A just went extremely dim. Oddly, it still cycles through modes, but it’s barely lit. If there was ever an ultra moon mode, I’ve got it now. Is this the sign of a blown LED?

you checked the cells in your multicell lights?

I officially have 3 blown lights now… and I have no idea why.

1. Roche LS01 (modded) - Samsung unprotected ICR batteries that I’ve used in this flashlight for almost a year now
2. Trustfire 500A (un-modded) - Sanyo protected
3. Uniquefire UF818D - Sanyo protected (same cells as above)

The Sanyo cells were fresh off the charger, but I checked them with my MM and they were both at a steady 4.19 volts.
The Samsung cells were at about 3.9 each. None of the cells have been mixed and matched. They’ve always operated in the same pairs. It’s nothing I haven’t done before. So strange………

Yeah, first question is always — what does your voltmeter (nowadays likely a DMM, ‘digital multimeter’) tell you about each of the cells?
Post the brand name of the cell, what the label says, whether the cell has build in protection, and the measured voltage of each and which ones were paired together in which light.

Have you tried removing the tailcap and checking with a paper clip from minus end of cell to light body, to rule out switch problems?

Does either of those lights have low voltage protection in the driver?

I just tried measuring amps on my MM with the tailcap off and I’m not getting anything. Checked some other single cell lights and they work just fine. All three 2*18650 lights are getting. 0.01 amps on a tailcap measurement.