With electrics, this can be confusing. You cannot put a switch between the battery and ESC unless it is one which can carry the high current. This would be a switch as large as the ESC with corresponding heavy gage wire. Now, some ESC's come with an arming switch which just enables/disables the ESC and this only switches a very small current but does not isolate the battery from the system; i.e. your battery will run down if you leave it plugged into the ESC with the switch in the "disable" position for a long time, not a problem if you are just using it to keep things safe while you are getting the plane to the flight line.