18650 battery problem
It happens like this... Friends, it turns out I was wrong in thinking that only batteries with a protruding contact are equipped with a protective board. There are also those with a recessed one. Mine just happened to have protection. This flashlight has been working for several years now, the batteries do not discharge to zero. However, I want to warn everyone: when choosing batteries, do not miss this point: the flashlight itself may not be equipped with protection, then you need batteries with such a board.