E-Bike Energy Consumption

Anticipating a lot of spare time and with rare good foresight, I bought an electric bicycle at the beginning of the COVID19 lockdown. I wanted a folding model so that it could be put into the car trunk and big wheels because the small-wheel folding bikes look strange to me. The Ancheer 26-inch folding mountain bike fit these specifications and was delivered in just a week. My timing was good because orders a few weeks later took up to two months to arrive.

Putting it together was fun and took less than two hours despite the cryptic instruction printed in a microscopic font. Everything was included though the assembly tools are best described as “disposable”. The brakes and derailleurs were properly adjusted from the factory. The hardest part was waiting 24-hours to charge the battery as instructed. This is important as the life of lithium polymer batteries is extended when the cells are leveled with a long initial charge.

There is a very active and well run support group for all Ancheer electric bikes on Facebook at https://www.facebook.com/groups/621212528377039.

The Ancheer 26-inch folding bike is powered by a 250-watt brushless hub motor on the rear axle and an 8 ampere-hour, 36-Volt lithium polymer battery. It has front and rear mechanical disc brakes and a 21-gear derailleur. Despite the aluminum frame it weighs 65 pounds (30 kg).

Riding an e-bike is exhilarating. Acceleration and hill-climbing are effortless and if you tire yourself with pedaling you can recover while cruising on electric power.

There are three modes of use: 1) pedal assist, 2) manual throttle, and 3) regular unassisted bike riding. In pedal-assist mode, a cadence sensor on the pedal crank signals the controller when you are pedaling and supplements your effort with motor power. Some e-bikes have up to nine levels of pedal assist, the Ancheer has three. At the lowest level, the assist is barely noticeable but helpful. The mid-level assist is a good compromise. The high level runs the bike to a higher speed than I can pedal.

I prefer the manual throttle mode. There is a twist control on the right handlebar that lets you control exactly how much power the electric motor will deliver. I especially like the throttle mode when crossing a busy street from a standstill as it will accelerate the bike very quickly when also pedaling.

Soon after I got my Ancheer 26-inch folding electric bicycle, I built the data logger described in another post: https://w4krl.com/e-bike-logger/ The logger directly measures battery voltage and current, and calculates wattage. It also records calculated energy consumption in terms of ampere-hours and watt-hours. It writes this data to a microSD card every second. The datafile can be opened in a spreadsheet application like Excel to analyze and graph the data.

I plan to make five runs over the same 9.7-mile (15.7 km) round trip course that is mostly paved trails and bike lanes with a short length of hard-packed unpaved trail. Most of the ride is uninterrupted though there are four street crossings that can introduce random delays. The course is relatively flat with a rise of 147 feet and fall of 141 feet.

  • Trip 1: All electric – the run was made mostly at full throttle with minimal human pedaling.
  • Trip 2: Low pedal-assist – to be done
  • Trip 3: Medium pedal-assist – the bike controller was set at the mid pedal assist setting.
  • Trip 4: High pedal-assist – to be done
  • Trip 5: Manual throttle – this run will be made mostly by pedaling with some manual throttle assist. This is my usual riding style.

So far I have made the All Electric Trip 1 and the Medium pedal assist Trip 3 with some interesting comparisons:

  1. Although the bike motor is rated at 250-watts, peak power is actually 400 watts. It appears that the controller limits battery current to 10 amperes.
  2. In the All-Electric mode, the bike uses 0.35 Ah per mile (0.22 Ah/km). If the battery has a true capacity of 8 Ah the range would be 22.8 miles (37 km). This agrees well with rides I made before having the logger. The average speed was 13.2 mph (21.4 km/h). Top speed with electric power only on level paved road is about 20 mph (32 km/h).
  3. The PAS Medium setting reduces energy consumption to 0.20 Ah/mi (0.12 Ah/km). This extends the range by nearly 70% to 38 miles (62 km). [Your mileage may vary!] However, average speed dropped to 11.4 mph (18.5 km/h). I also noticed that there was NO motor assist above 15 mph (24.3 km/h).
  4. Although PAS Medium limited assist to speeds below 15 mph, there was no limit on the peak power of 400 watts.

I will conduct Trips 2, 5, and 5 as time and weather permit. My expectation is that the main difference between the three pedal assist levels is top speed. This is 15 mph for PAS Medium and will probably be full speed for PAS High and a lower speed for PAS Low. It will be interesting to see how the range is affected.

Trip 1Trip 2Trip 3Trip 4Trip 5
ModeAll ElectricPAS
Low
PAS MediumPAS
High
Manual Throttle
Date8/8/2020 8/14/2020  
Data File (csv)Bike8 Bike11  
Distance mi9.7 9.7  
Time2640 3053  
Speed mph13.2 11.4  
Amp-hours3.43 1.96  
Watt-hours128.9 76.5  
Amp avg4.68 2.31  
Watt avg175.8 90.2  
Ah/mi0.35 0.20  
Wh/mi13.3 7.9  
Range ratio1 1.68  
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