How closely did you monitor it? I am curious if it didn't ramp up to the full 10 amps or if it took a long time balancing it. I have had some batteries just have a bad attitude about balancing. They will charge fine (in the correct amount of time), then sit there and balance back and forth for like 20+ min. A full charge / discharge / full charge (or two) will normally sort them out. If on the other hand the charger doesn't want to go up to the full 10 amps, I would be concerned something is wrong with the battery.