This video shows how to measure the Efficiency from an electric motor (at full load) using a VESC6 controller which provides some telemetry. Sportdyno provides direct integration with this telemetry (for VESC Firmware version 1.0). We use the input voltage and current to obtain the Input Power. Motor efficiency is (mechanical) Engine Power divided by the (electrical) Input Power. Efficiency is measured as a "black box" (controller and motor are cosidered a single part as controller efficiency is typically high, say 97 or 98%).
Many Electric controllers provide this kind of telemetry, Sportdyno supports *any" CAN based and CANopen based telemetries and others based on UART. But in the case that the controller does not provide telemetry (or the protocol is not available), these two variables must be acquired directly. Voltage can be easilly obtained with a resistor network up to 100V or so, while current normally is obtained either by a hall sensor (for high currents: 50 or 100A) or a shunt for lower currents. Some of thermocouple differential inputs can be reconfigured to measured low voltages from a shunt resistor.

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