I was using my Wurkkos TS22 with low battery and I placed it upright on a table. The moment it made contact with the table it suddenly got much brighter and after a few seconds it began to flash rapidly as if it was in strobe mode.
I picked it up again and pressed the switch repeatedly but the flashlight was unresponsive. I unscrewed the tail cap and it finally turned off. I screwed it back in but to my surprise it started flashing again.
I was unable to get it to stop and even when I tried to charge it, it kept flashing.
I swapped its battery with a fully charged one from a different 21700 flashlight, then it was fine and I couldn’t reproduce the problem… Until that battery was also low. Giving the flashlight a light slap causes it to “reboot” at the full brightness of whatever mode its in. If you’re in High or Turbo it will lock up and rapidly flash. The flashlight can not be turned off or charged. Under voltage protection will not kick in!
I have had the same behaviour when using it from usb-charger only, without battery. When ramping up it starts flashing when its not getting enough current, I presume. Only way to reset it is starting it with full battery. I changed mine to 3000k XHP70.3 HI and I like the light and use it a lot as worklight and offroad bike light. But it got some shortcomings in the driver, some times ramping it just glitches to moonlight. The drain issue and there ia not really a low…
My guess is hitting it might compress the spring enough to make better contact with the battery and briefly trick the flashlight into thinking it has higher voltage. Why it strobes like that after idk. Not enough power to run the chip maybe.
I wouldn’t trust that multimeter too much, but if it’s strobing like that after low voltage kicks in that 2.1v probably isn’t far off. The charge controller in the flashlight might be set to not charge a battery when it’s that low. And you probably shouldn’t anyways. Not one of these cheap ones. And definitely not at anything other than a really low amp recovery charge