minecarts cannot make it up long slants with powered rails

(This affects the version beta build 7) Minecarts cannot make it up my slanted track. The track is 50 blocks high and it only makes it up 23 so about half way up. on my other tracks that are smaller the minecart will make it up it is just the longer one. When it gets about half way the minecart will stop and go back to the bottom. The track is all made from powered rails so it all should have power. My device is a Samsung galaxy s4.