I just received one of the bargain $9.99 eGo Style 900mah batteries. The one that I got wouldn't work with most of the DC Cartos and Clearomizers that I have, nor would it charge without a V2 Shorty Extension. The center post (positive) wasn't making a connection. I had heard that some of the batteries had this issue and some didn't and that was the main reason MV put them in the bargain bin. People have been filing down the battery connector or using the V2 Shorty's to correct the problem. I took a small screwdriver, pulled up the center post and viola, it works with anything I've put on it so far. It even fired up the eGo Mega Dual Coil Cartomizer. Just be careful not to pull the center post out too much or you may damage the battery. A little bit goes a long way.