Tank cartos are different and may need the battery post raised. It's not necessarily something wrong with the battery. It may work with some cartos and not others. I'd still recommend trying both to see what happens. Just make sure you are careful and don't disconnect anything. I don't have an Ego, so I don't know how easy it is to raise a post on them.
I use the same method that I use on the stealth manual. I take a needle or pin and just wiggle the post up a bit by placing the needle thru the outside of the holes going into the post. I make sure to go into every hole at least once.
That seems to work for me. Good luck.
Ddrocks sir it's one of two things, either the post needs adjustment or the carto that came with the tank is bad. Do you have a multimeter around?