Shen Qui Wei/ Panther problem

[Darius2250]

I know the title is lacking, first I am not to sure what I have, the bullet say Shen Qui Wei , but the recipt says it a Panther, this is my first mirco racer so I don't know if there is a difference or not,
anyways on the problem, I bought 2 of them and they both seem to have the same problem, I charge them they go really slow(thought this might me a motor deal the guy said they were 1.2's)but then they just stop.if I bump them they will do again, is this normal behavor? or should I be taking them back?

Thanks