Battery can not hold the load capacity

Once this battery has mainly received very good reviews, I ordered the battery on 12 February 2013, and charged with the original charger for Lumix FZ 200. After wandering the battery - as a reserve battery - in the camera bag.
Two days ago, then his first mission with the FZ 200. battery was inserted and the indicator on the display indicates full charge.
After 20 minutes of film operation was made. The camera monitor turns off and signaled Battery charge too low. Hardly understandable as the genuine Panasonic battery with its 1200mAh in practice loose brings more than ten times the performance.
Something's wrong here.
Either do not match the 900mAh stated on the battery or the battery has undergone an extremely strong self-discharge in the 6 months.
From the charging indicator, it was not apparent and with a Li-ion battery, this form of self-discharge may not occur.
So battery is charged again and tested when the front camera monitor. The result was slightly better but still unsatisfactory. The battery pack discharges too quickly. Therefore, only one star.