Not to derail the thread, but what's the physical difference between the grey ultrafires and the black/red trustfires that makes ultrafires trip protection while the reds don't? Both are protected, are they not?
I was messing with an eGo mega dual coil carto earlier today that my brother has (with a 510 extender) and anything over 4.2 volts tripped the protection after a half second burn with my grey ultrafires.
Do the black/red ones last longer at all? How about the AW IMR batts (sold from other retailers)? I noticed the IMR batts are only 600 or 750mah (from the few sites I found selling them, labeled mAh differs), and right now I'm swapping these 900mah batts twice a day, which is annoying because a 900mah eGo clone batt would last me over two days. =\
I have my box marked to my common voltages. I bored a small hole above one of the parts of the phillips indentation and then turned it to the voltage I wanted and took a razor blade and marked a notch on the box. Line up hole with notch and I know where I'm at. 4.2 and 4.8 are currently marked, and I know I can go a smidge down for 3.7 or a smidge up for 5. +- .2v is hardly noticeable anyways in the 4.x range, so it's not a big deal.
Also: I picked up a multimeter from madvapes with mine, but I wouldn't recommend the one they sell. Very cheap quality (expected for $10) and I need to resolder both leads already because they just popped off. It's not worth it to bother with a return/refund, since it's something I can fix myself, but alas...