I've never used that charger, but it looks alright. Too bad it doesn't discharge. The reason it seemed to have more power after the 4amp charge is, because when you charge a battery at a higher rate you get more punch, but less run time. If you had a discharger I would recommend you cycle them a few times and then see what happens. It sounds like your charger may be false peaking. If you know someone with a discharger borrow it so you can cycle your batts and then see what's up.