Loading slow

I am for several months in possession of this battery, and use it about once a week, sometimes less.
However, I must say, it loads much slower than I am used to from the wall outlet.
WHILE the use of my cell phone (surfing, music) he invites my HTC Desire X as good as not. In half an hour one percent, at 2A connector on the battery level drops even 0.6A.
With ausgeschaltenem display the battery, roughly invites at half the speed as the HTC adapter with 5V 1A.
My conclusion: Maybe my battery is faulty, or I use it enough, in any case does not result in the charging rate I expected at 5.1V 2A.
Nevertheless, at this price a useful product. ;)