I don't know where you got the batteries to begin with and only mention that fact because recently I was looking for a replacement battery for my Moment.
There were some advertised for like 5 bucks apiece. The reviews on them were all over the place and the story seemed to be that they were some kind of 'seconds', defective in some way and didn't make the cut. That is why they were so cheap. some people got them and were lucky, others went through 3 or 4 before they got a good one.
Don't know if that applies.
Otherwise, I sure do suspect the charger though. Not sure how you could check it though. Seems like if it was overcharging, your batteries would get noticeably hot.
I have read some folk who claim to know what they are writing about say that actually fulling discharging batteries w7y as not a good thing. That might have been laptop batteries though. That being said, I read where one idea was to freeze a laptop battery to get more use out of it. don't know if that really works or where I read it, but I'd study up on it before I tried it.
let me know if you try it and it works. If it blows up or something, let me know that too.
edit: He put it in ziplock bag,
Freezing Laptop Batteries A Philosopher's Blog