Under 250 dollar brushless Ebike
 

I want to make one of these but cant find a lipoly battery pack that lasts at least 30 minutes can any body help me

what size of lipo are you searching for ?
how much volt do you wana use ?
what motor ?
how much money do you wana spend..
and so on and so on..

with your post with nearly no information inside, not even a question its hard to help...