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Assistance Factor and Mountain Range

A worldwide unique test with live test rides over two different test routes and with the latest measuring equipment. Conducted by Frieder Herb and Kerstin Bünte, ExtraEnergy, in Kirchheim/Teck, Germany.


How we tested:

1. Preparation:


• Charge-discharge cycling: Charge with original charger,   discharge with electronically controlled discharger.

• Solder measuring cable onto the battery cells to   measure electricity flow during the test.

Each test bike was equipped with the following:
• Handlebar bag with tools and an on-board data   collector and transformer

• Palm-Computer for recording speed, pedaling rate, and   pedaling power

• Special pedals to measure the exact amount of the   rider’s muscle power. The data was transferred via   radio to the on-board computer

• Sensors to measure pedaling rate and speed
• Cyclosport Hack-4 for pulse

Further steps:
• Calibrate pedals with a comparison weight

• Attach cables

• Check tire pressure 

• Set the Palm-computer for the corresponding wheel   circumference

2. Riding Tests

Everyday Track

The 5 miles long route in Kirchheim/Teck is mostly flat and has a short incline up to 8%. Here, motor assistance factor was measured.

Mountain Track
The 1/3 miles long route begins with an 8% incline and then decreases into a 7 % incline. Here, assistance factor and mountain range were measured.

Assistance Factor
Pedaling power and avereage speed of a regular bicycle were recorded on the defined test tracks. The measuring data of the test pedelecs were compared to the measuring data of the regular bicycle. The assistance factor expresses the difference between these data.

Assistance factor 1 = The motor doubles rider’s power.
Assistance factor 0 = The motor only compensates the additional weight of the drive unit.
Assistance negative = It would be easier to ride without electric drive unit.

Measuring the Assistance Factor
Determining the reference data:
Three test rides were done on a standard bicycle without electric drive on the determined test tracks:
1. Ride: Slow with low muscle power
2. Ride: medium speed
3. Ride: fast (max power of the rider)

During these test rides the relation between average speed and the rider's muscle power was measured. The data was linearized into a straight line which helped to  calculate how much muscle power is required for different average speeds. 

Determining the assistance factor of  a pedelec:
The same three test rides on both tracks were done with all test pedelecs. Muscle power and average speed were measured. The difference between muscle power and average speed compared to the non-electric bicycle is what the assistance factor expresses. It refers to the used electrical energy. The assistance factor also expresses positive characteristics of a bicycle such as low air resistance.

Formula to calculate the assistance factor:
Click here to enlarge

ub = Assistance factor on hills
ue = Assistance factor on the flat
vpe = Speed of pedelec/e-bike in kilometers/hour
lpe = Rider’s muscle power on pedelec/e-bike in Watts
(Abbreviations based on German explanations)

Measuring the Mountain Range

On the mountain track, riders rode uphill until the battery was empty (downhill the riders coasted).

3. Evaluation

After each test was completed, the data (speed, power and pedaling rate) were downloaded from the Palm-computer to a PC, and evaluated. 

This description refers to the Pedelec and E-Bike Tests of 2002 and 2006



7 - 12 September 2021, IAA, Munich, Testtrack

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