Most of the E-stops are rated at 10A or less. The following blog has explained how to wire an emergency stop http://www.ehow.com/how-does_5151421_do-emergency-stop-buttons-work.html.
But from my understanding of this circuit, the E-stop is still in series with the power-supply. Given the fact that the amount of current most E-stops can handle is so less (~10A), How is it possible to wire them so that they can be used for high-current electrical system?
Also, by wiring the emergency stop in series with the main power source (batteries) would violate the safety principle that resetting the emergency stop should not by itself turn on the power again.