Airsoft thompson m1a1 battery question,?

So i bought this gun at big5 yesterday for about 150$. when i took it out of the box i didnt really have knowledge of the battery being precharged. so i charged it for about 5 hours as it said in the manual. then it fired like 4 times semi auto very weakly then i charged it for about 3 more hours went to sleep and it still is doing anything. did i overcharge it or not enough? has any one else had this problem. is it broken?