EBTL Test Method - Setup, Instrumentation, Hill Climb Peformance, Acceleration and Braking

EbikeTestLab

New Member
This post explains how I setup each ebike for testing and how the acceleration and braking tests are performed:

Ebike Setup and Instrumentation

Each Ebike is setup with all of it’s factory supplied equipment such as fenders, rack, lights, and factory pedals. The total weight is measured with and without the battery or batteries using a calibrated scale. The computer settings, if any, are left at their factory default level unless noted in the test report. The tire pressures are set to the recommended pressure in the owner’s manual, or to the middle of the sidewall listed range if there is no recommended pressure stated in the owner’s manual.
The factory pedals are then removed and power meter pedals are installed. A Garmin Edge cycling computer and Vbox GPS unit are installed on the handlebars. The weight is measured again with the installed instrumentation. The rider weight with helmet is also measured and noted in the test report. I’m a big guy (6′ 3″ and 190 lbs) so my target weight for rider, helmet, instrumentation, and water bottle with cage is 200 lbs. I adjust the water bottle or bottles to reach that target for every test, unless noted separately. For the durability and real world range testing, I may also add a pannier bag or backpack with laptop that adds another 10 lbs for a total additional weight of 210. This will all be noted in the test report for each individual bike.

Acceleration

After initial setup and instrumentation, the battery is checked to make sure it is charged to 100% and battery voltage is recorded. The ebike is then ridden on zero assist to a nearby flat stretch of asphalt paved rail trail. There, it undergoes acceleration testing, where several are made for each acceleration type (throttle, zero effort pedaling, 100 watt pedaling, 200 watt pedaling) with an even number of runs performed in each direction.


For the throttle only accelerations, the throttle is placed at maximum from a dead start and the ebike is allowed to reach it’s maximum throttle assisted speed. If the ebike has a cadence sensor, acceleration to maximum assisted speed is also measured while spinning with zero load and the PAS set to max. If the ebike has a torque sensor, acceleration is measured while pedaling as lightly as possible.


Acceleration is also measured while averaging 100 watts of pedaling at an average cadence of 80 rpm, and then finally with an average 200 watts of pedaling at an average cadence of 80 rpm. Results are calculated from the 20 Hz GPS unit and the power pedals. The acceleration times for each are reported as a single average along with the average power and cadence as appropriate. Runs are repeated as necessary to achieve the desired power and cadence. Shifting is performed as needed to meet the target power and cadence.

Hill Climb Performance

Ideally, we would have access to a set of constant grade hills, such as those built at an automotive proving grounds. Lacking a set of these, the hill climb performance is measured on a particularly long uphill road, Ice Pond Road. Starting near Route 312 in Brewster, NY, Ice Pond Road then climbs 325 feet in exactly one mile. The grade averages 6% but portions are as steep as 25%. This is a segment on Strava as well, simply search for “Ice Pond Rd” in Brewster, NY.


After confirming that the battery is fully charged and the voltage recorded, the ebike is started from a marked spot near Route 312. For the throttle only climb, no pedaling is performed. The time to reach the top of hill is recorded or, if it can’t reach the top of the hill, the total distance traveled is noted. If the ebike does not have a throttle, this first test is performed with no pedaling effort applied, simply spinning along to activate the cadence sensor. For bikes with torque and cadence, this test is usually skipped. The hill climb is then repeated with pedaling an average of 100 watts at 80 rpm (or lower if gearing requires it). The actual pedal power will be reported for each result.

Braking

Once the acceleration tests have been completed, the braking distance tests are performed on the same flat stretch of asphalt paved rail trail. The ebike is acceleration to it’s maximum assisted speed. Once the front wheel crosses a line marked on the pavement, both brakes are applied to their maximum level. In many cases, the rear wheel will lift off of the ground. Once stopped, the distance from the line to the bottom of the front wheel are measured and recorded. This is repeated as many as needed to have at least 3 stops in each direction without any major outliers.


Now, I understand that rider skill has a lot to do with braking distances. However, braking distances can vary due to tire compound, type of brakes, and road surface. Brake tests are only performed when the asphalt surface is clean, dry, and the surface temperature is between 50 and 80 degrees F. Due to the variability in these tests, they should serve as only a guideline but it helps to understand how quickly a certain ebike can be brought to a stop.