This works great for the Sunwayman F40A, NiteCore EA4, etc. or similar Series-running lights to completely lock it out to eliminate the parasitic drain:
After receiving my F40A, i did the same mod i originally did with my Nitecore EA4W to add a tail cap lock-out to eliminate the parasitic drain for log storage periods.
-for a stock light, begin by clipping off half of one of the tail cap negative-terminal springs, then test with the cap in place, then progressively clip off 1 mm more each time, until its the right length that when you unscrew the tail cap one turn it loosens contact for the one cell, thus locking out the light. ( shaking the light you should hear a light movement of one cell when locked out)
Once you get the proper length that works for a tail-cap lock out, you can file off the sharp edge, or add a copper braid to the spring for increased current capacity.
I have been testing this method with my EA4W since last February, and its working great at eliminating the parasitic drain known for the EA4 series, without hindering performance. (It also may work with other multiple AA lights running in series configuration.)
