It rans fine for a few minutes and then it stops.

It rans fine for a few minutes and then it stops.

Battery pack is fine all three Lighs are on indicating power pack is charged and ready to go but it only lasts for 3 to 5 minutes. I have tried another charged power pack, and it does the same thing.

It's a nice machine but I am very disappointed that I can't use it for too long please help me out! what is the problem?