I posted this elsewhere, but got no response whatsoever. I thought I would post it here, as I know someone here can quickly answer this question. What will happen if you put one 3.7 battery in a 5v regulated mod (specifically, an ego e-power 5v regulated, which takes two stacked 16340s). My brother bought one and doesn't like 5 volts. I know there are some 3.7 volt batts that will fit the battery casing, but I don't know if it will fire that way. Will it? Thanks for any help.