Descriptions of key points related to driver function. If the driver has failed after use with Li-Ion rechargeable batteries instead of lower-voltage CR123A primary batteries, there are two options for repair.

If the voltage boost circuit has failed, the driver can be restored to full functionality (albeit LI-Ion only, no more primary batteries) by connecting either Vcc to Bat+ or by bridging Vin to Vcc (in the latter case, all current will flow from Bat+ to Vcc via the inductor).

If the microcontroller has failed, the flashlight can be turned into a single-mode direct-drive flashlight by connecting LED+ to Bat+ (LED- is already directly wired to Bat-).