Minecraft wiki entry for Rail, associated text: A minecart with no rider at full speed can climb 10 blocks on an unpowered track. This suggests that a powered track is needed at a height of only 10 blocks to keep a cart climbing. However, the cart slows so much that it can reach only another 5 blocks high with 2 lengths of powered track starting at 9 blocks high. The minimum number of powered rails to keep the cart climbing perpetually is 3 every 6 blocks.