The minecart take domage when he was on active powered rail.
What I expected to happen was...:
When i builded à clasic railroad i found this bug in my survival map.
What actually happened was...:
The minecart take domage when he is on active powered rail, eject the player outside the minecart but he is not destroy and he is not propel.
Steps to Reproduce:
Put a minecart (for player only) on powered rail and active the rail with redstone.
Are you sure it was a powered rail and not an activator rail?