SPDT toggle switch
This single pole, double throw switch with centre off position, can be used in the circuitry inside your loco to act as an on-off switch for the receiver with the added bonus of also connecting the battery to the charge socket when it is flicked in the other direction 
Conventionally, the switch is wired into the positive lead from the battery, the battery lead being connected to the centre terminal. One of the outer leads is then connected to the receiver and the other lead is connected to the positive terminal of the charge socket.

The positive battery terminal is thereby either connected to the receiver or to the charge socket (or to neither when in the central position). This helps protect the receiver from any spikes in the current when the battery is being charged.