In the previous post “Range for Speed” it was explained that high speeds dramatically decreases range. If you want to travel far, it is advisable to reduce speed. The post became a blockbuster and is now followed up with episode two (Range for Speed 2) to answer questions about consumption in low speed.
The first post tested differences in consumption between 80, 100 and 120 km/h. The tests were done on the same stretch of road with the same wind, temperature, etc. The car was on cruise control in all tests. It turned out that the power consumption increased 25 % when the speed increased from 80 km/h to 100 km/h and in 120 km/h it was more than 50 % higher.
In Part 2 of the test, we have now examined the difference in consumption between 40, 60 and 80 km/h. Also this time the conditions were the same and the car was running with cruise control at the specified speeds. The results show that even at low speeds the difference in consumption is significant. The car consumes 15 % more energy at 60 km/h compared to 40 km/h. At 80 km/h the consumption has increased by 40 % compared to the 40 km/h.
For practical and safety reasons it was difficult to test the low speeds on the same road as the high speeds. However, since the consumption at 80 km/h was almost identical in the two tests I have paired the data series. From this we can conclude that consumption is 120% higher at 120 km/h compared to 40 km/h!
The figures become very tangible when converted to range. If we assume that it is possible to travel 100 km at 100 km/h (given a certain temperature, wind, road conditions, etc), it should be possible to go 25 km further if speed is reduced to 80 km/h. At 60 km/h it will be possible to go 155 km and at 40 km/h all 180 km.
The range for speed relationships is found to be almost linear and flattens out only very marginally at low speeds. It can therefore be concluded that if you want to beat a range record with your i3 you should drive as slow as possible. However, if you need to travel far and want to arrive quickly, it is certainly a better strategy to drive fast and take a 20 minutes pause by a rapid charger.