Faulty Trakpower?

[himalaya]

The part that I am worrying about is the voltage increased so fast during charge, that clue suggests your pack's IR may as large as hundreds of miliOhms, which I experienced only with very cheap low rating low cap cells(2~3C, none RC-type, like the one insde your ipod).

[Patrick]

Originally Posted by himalaya

The part that I am worrying about is the voltage increased so fast during charge, that clue suggests your pack's IR may as large as hundreds of miliOhms, which I experienced only with very cheap low rating low cap cells(2~3C, none RC-type, like the one insde your ipod).

Yeah that's what I was wondering as well. The higher the resistance the more voltage you need to push a certain current, and since you can't let your voltage go higher than 4.2v per cell, it limits the current you can charge at. So if you can't charge at at 1C then there's too much resistance somewhere.
I'd check your bullet plugs aren't loose when plugged into the pack, because those things loosen up sometimes and that could possibly cause some extra resistance that's only noticeable at higher amps. If you can't find anything like that, then it could be high IR like himalaya said, and it could be a faulty pack.