EBTL Test Method - Road Load and Real World Range Evaluation

This post explains how I test each electric bicycle for a calculated road load range and determine the real world range:

Road Load and Calculated Range

Once the brake tests are completed, the road load tests are completed. The purpose of the road load test is to determine the power necessary to propel the ebike at various steady state speeds over a flat section of smooth asphalt. To do this, the assist is set to zero, or off, and ebike is pedaled at a steady speed over a flat section of asphalt in both directions. Typically, the ebike is pedaled at 5 mph in both directions, then 10, then 15, then, 20, then 25, and then finally, the top assisted speed, which is typically 28 mph. Several repeat runs are made to assure statistically significant data (I know that varies by statistician, I use a t-test of 95% or greater confidence for significance).

Once the data is collected, the average pedal power is calculated for each speed. Efficiencies are then taken into account so losses from the battery through the controller and motor can be calculated. Finally, a battery wattage per speed chart can be made. Using the manufacturer’s published battery and amp-hour figures, one can then calculate the range for any given speed (for flat ground of course).

Real World Range Evaluation

There are two styles of real world range tests that can be performed. In both cases, the battery is charged to 100% and the voltage is recorded at the beginning. For the first test, the ebike is ridden on max assist on the Putnam and North County trails from the test lab to White Plains Road, a distance of 36 miles while the rider contributes an average of 100 to 150 watts or so. The voltage is then recorded at the end if the low voltage cutout isn’t triggered. If the low voltage cutout is triggered, the total distance traveled is recorded. The average speed, pedal power, starting and ending voltages are recorded and reported. These results will all be noted in the test report.

The second style of real world range testing involves riding around a closed loop set of roads at various locations until the low voltage cutout is reached, again while averaging 100 to 150 watts of pedaling. In this instance, the ebike will continue until the low voltage cutout is triggered. The average speed, pedal power, starting and ending voltages are recorded and reported.