Measuring the Efficiency and Power of your Electric RC Helicopter Power System

To get the most out of the electric power system in your electric rc helicopter, you will need to know if any of the components are under-powered, or over-powered and just adding weight। This article discusses what you can measure, and how you can measure it. This article is fairly advanced. We recommend reading What Does An Electric Power System For An RC Helicopter Consist Of first.

Each component of your power system is good at something। Are you taking advantage of each of them? A 25A speed controller in a small coaxial helicopter with a motor drawing 5A is not being used properly. By measuring your electric power system you can discover mismatched equipment and correct it. In this example, a 10 amp or 7 amp ESC would save weight.

Measuring the Electric Current in Your RC Helicopter
The measurements you are interested in describe the flow of electric current (using unit of Amps, A), the electric potential (using unit of Volts, V), and power (using units of Watts, W)। These can be measured with a wattmeter. A wattmeter can be inserted between your battery and speed controller and it will tell you the voltage, current, and power drawn from your battery. Measurements should be taken when your helicopter is at full throttle. For RC hobby use, there are small wattmeters that can be installed in you aircraft, and can log measured data over the entire flight. These are called flight data loggers, and in addition to current and voltage, they can measure rpm, temperature, and more with the addition of the appropriate sensors.

Measuring Current And Voltage in Your RC Helicopter
The current reading should be within the limits of the speed controller, battery, and motor। The voltage indicates how your batteries are performing. Usually you can confirm your battery is adequate by noting that current is below the battery’s rated max current (For Thunder Power batteries, this would be the continuous rating, not the burst rating). This rating generally says ‘this battery model is approved for this use,’ whereas voltage says ‘this battery is performing as expected’ or ‘this battery can’t handle this.’ As a rough guide, your lithium polymer battery voltage at full throttle should be above 3.3V per cell (i.e. a 3s lipo should be above 9.9V).

Measuring Temperature in Your RC Helicopter
The temperature gauge is used to tell you the temperature of your motor and batteries। For both, the key temperature is 60°C (140°F). Both should be under that temperature. Above this temperature, lithium polymer batteries are permanently damaged, while motors lose efficiency and become dangerously close to demagnetizing and burning the windings. However, being too cold isn’t ideal, either. Cold is a sign that the motor isn't being properly used (i.e. it's too big), and cold batteries don’t put out as much power as 50-60°C batteries.

Tips
* Put together a power system that is slightly conservative
* Test and measure that system, and then adjust based on those measurements
* Currents will be near every component's limit, and temperatures after a flight will be ideal
* At that point, every component will be played to its strength।
* Have fun flying!