Why does the TK21R downshift to a lower mode after being used for a while and the higher mode cannot be selected?Updated 10 hours ago

There are two reasons:

1. Intelligent Overheat Protection

The flashlight will accumulate a lot of heat when used at high output levels for extended periods. When the light reaches a temperature of 55°C or above, the light will automatically step down a few lumens to reduce the temperature.

2. Low-voltage Warning

When the voltage level drops below the preset level, the flashlight is programmed to downshift to a lower brightness level until the Low mode is reached.