Musings on the impact of speed on range

[ROJA]

I could have sworn I posted this last week, but it seems to have disappeared...



MY BOLD HYPOTHESIS: It seems like riding hard at 25-28 mph (steady speed on flat routes) really kills your range, even more so than hills. This makes sense because the motor is working hard all the time (especially due to the increased wind resistance), versus on hilly routes where the overall speeds are lower and the motor can "rest" on the downhill sections.

My longest ride was one with around 3,000 feet of climbing, where I managed to get 32 miles of range. On flat rides where I'm going 25+, my battery goes down at the rate of roughly 3.5 - 4% per mile (Eco70), which would give you a range of 25-28 miles. Full Turbo mode (100) seems like it increases the draw to closer to 5% per mile.

I think that much longer ranges would be possible at lower speeds (say 17-21 mph). I just seldom have an occasion to go that slowly (if so, I'd take my non-e road bike).

Has anyone thought or played around with this? I think I need to experiment a little more...

(Note: This is with a 2016 Turbo X, but I'll bet the results would be relatively similar with the other Turbo models.)

 

[Bicyclista]

You did post this last week ("It's deja vu all over again," as Yogi Berra would say), and most of the replies agreed with you. I do.

 

[Richard Spensley]

Well I actually thought the opposite and I'll try to explain why.

Normally I commute about 18-20km each way and this uses anywhere from 40-50% of the charge (from full, 98%) depending on wind direction. This is on mixed hills and flat with a total climb of ~150m and a total descent of ~200m (the other way round on the way back). I find that the amount of battery used is almost the same in each direction, even though there is more of a climb on the way home. I ride as hard as I can and complete the distance in ~29-35 mins depending on traffic, averaging around 36km/h-32km/hr. Often (especially downhills but even along some flats and slight declines) I am riding faster than 45km/h which means that the motor stops and I am under my own steam.

The other week I took a different route as I needed to visit the dentist and so I thought I'd try riding "easy", not really pushing at all and just kind of going through the motions to see if I could turn up at the dentist without being a sweaty mess. The 17km route there is relatively flat with no steep hills and I had an average speed of only 28km/hr. When I arrived at the dentist I noticed that, instead of using less battery than normal, I had used nearly 60% of the battery!

I know this is totally unscientific but I would say that lower speeds (taking it easy on a flatter route) actually use more battery than if you rode the same route riding hard out. More testing obviously needed. I'll ride the flat route again soon and ride it hard out to get a definite like-for-like comparison and I'll try riding my usual home route easy to see what this does too.

 

[ROJA]

Very interesting. I'm going to try the same thing at some point (taking it easier) to see what happens. I'm also going to try going hard at a low assist level (maybe 40%) to see how that impacts both battery and average speed.

 

[ROJA]

Interesting- I think I usually use about 16-25 Wh/mile (cruising at 25-28 on the flats but averaging around 20-21). I will try some other combos to see how it goes.

 

[bazzapage]

I found with the base Turbo motor that going hard-out conserved battery. My explanation is that I am adding more energy per distance travelled than if I had been pedalling moderately, and the motor 'gives up' around 42-43kph. Of course tooling along at normal bike speeds is ultimately low consumption because of very little energy requirement overall. Which is why Bosch-powered bikes have such good advertised and real-world range (they cut out at 25kph).
With my Turbo S motor however, it keeps pushing hard when I am pushing hard, so it uses more juice when I am going fast. That's why you need a bigger battery.