I purchase a couple of generic batteries (different brand from different suppliers) for my M9. They were good for only a single charge. I then learn from RFF that they have similar experience. As for purchasing used re-chargeable batteries, two things to consider: 1) number of charge - good for 1,000 charge or so, and 2) year made - performance drops significantly after 5 years regardless of the no. of charge.
John