I had the same thing happen to me, but I lost 4 eGo batteries 2 900 and 2 650 mah.
Are you using a standard charger adaptor or the USB rapid charger?
Mcquin may be correct in his assumption about the contacts. Just be careful in not over tightening.
Regardless, I was never able to revive my 4 dead eGo batts, which lasted no more than a month.

Since then I purchased some more, including the what is known as the passthrough version, and knock on wood, so far, so good.
With all that being said, for dependability, you can't beat a good mod, such as a screwdriver. And are
not any more expensive than an eGo.