I got a flashlight as the first ever kind gesture from my apartment management for the most recent schedule 24+hours maintenance power shutoff. It has a very nice reflector for a square LED and a smaller chip inside that controls the 3 operating modes. 

Off course I had to open it up right away.  It uses 3AAA on the usual battery holders for cheap flashlights.  I smell trouble or an opportunity for some corrective active.  I am not fond of using odd numbers of AAA batteries as I have been using rechargeable since NiCd days.  I don't know if they use a constant current driver, so could be trouble for 3 fully charged NiMH (1.4V x 3 = 4.2V) with low internal resistance.

I used the parts from a 5V booster board I bought from the usual places, but modified the feedback divider for 3V which is just bright enough to drive LED, but low enough to not go into thermal run away.

U1 has the same pin out as the unknown part used on the board.

As my replacement board has 3 contacts - 3V and 2 GND, I had to move the battery off centered to avoid shorting the 3V output to the front of the PCB.  

I used easily soldered and bent metal strips  to form a battery guide and the hinged -ve terminal.  They are used to crimp the end of plastic mesh for store bought onions and garlic.  

My battery terminal help to make better connection between the offset battery and the spring loaded terminal the of the flashlight cap to the right side of the picture below.

It also acts as a pull tab for the PCB assembly when it is time for replacing battery.