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I'm using an electric bicycle to go to work. My goals are:

  • Not to arrive late
  • Not to sweat (too much)

My bike, like most e-bikes I guess, let me choose the level of electric assistance that I wish. I understand that the range is longer with a lower level of electric assistance. But in my case, this is not relevant. My battery can take the whole commute regardless of the level of assistance.

Is there any reason I should not use always the maximum level of assistance? For instance battery or motor damages/heating/...?

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    I use lower level of assistance only when the battery power drops below optimal level and I had no chance to recharge it. – Alexander Sep 18 '18 at 11:24
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    @Alexander a good time to use little or no assistance is if you think the battery is a little low and you'd like to save it for a hill – Chris H Sep 18 '18 at 15:08
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Assuming you have a good quality electric assist bike from a major manufacture. The manufacturer provided the max assist setting, so they intend for it to be used. It's a safe bet the bike is built to take the max assist torque without sustaining damage or accelerated wear. If the manufacturer believes sustained use of max assist will affect the bike, it will say so in the manual, so check that.

The one thing I'd be mindful of is battery life. General advice for laptops, phones and other portable devices is that deep discharge and heat degrade batteries and shorten their life-spans. If your commute is short, and the battery capacity is adequate for max assist both ways, that should not be a problem. I'm not sure about how discharge rates affect battery life - if I find info on this I'll update this answer.

Otherwise I say go ahead and use max assist. Yes, more torque and speed will wear bearings, chain, etc. proportionally faster, but using the assist is what you bought the bike for, right?

  • Battery management systems should be set up to avoid damagingly deep discharges anyway. – David Richerby Sep 18 '18 at 15:49
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    Battery care suggests not leaving an Li battery (assuming that's what yours is) fully discharged for any length of time. However, if you charge (at least a bit) immediately after use, that should be fine. electronics.howstuffworks.com/everyday-tech/… – James Bradbury Sep 18 '18 at 16:15
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I don’t always use full assist for the following reasons:

  1. Range and Battery life. I can almost double range by biking more. This is especially the case when I’m down to 1-bar on the battery level so I pedal on the flat portions and keep the assist for the climbs.

  2. Exercise: sometimes you wanna ride a bike, get those juices flowing

  3. Go faster: my ebike has e-assist capped at around 25km/h. So while I’m not deliberately dropping the e-assist level, the bike does so for me as I approach 25kmh. If I want to go faster, I have to pedal.

  4. Stealth: especially on bike trails, I’m conscious of being on an ebike even though I only go at bike speeds. The whirring of my geared hub motor is quite noticeable.

5

Too much assistance makes riding at slower speed uncomfortable.

For instance, if I select 15 km/h speed on a flat good road because of any reason (people walking there, nice views around, staying with the group that picked such a velocity, etc), full assist accelerates me too much. To slow down, I need to stop pedaling, then the velocity drops. Then I pedal again, the velocity increases and goes over the desired limit again.

These rush/slow iterations are annoying, it is much more comfortable to select the level of assist that matches the needed speed. Do not let the stupid engine with no eyes to decide which velocity is the best for particular road.

I think it is not a simply "bad controller" issue. There is certain amount of power the human can comfortably contribute without thinking about and much less may be less comfortable. Turning pedals with no resistance yet precisely at required speed needs more attention. In some degree this can also be fixed by shifting to the higher (not lower) gear - takes less power from the engine at the same speed. But gear alone seems not good enough for all cases.

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    That says something about the control system on your bike. Some are effectively on/off, some sense torque, some sense cadence. Different sensors suit different riding styles – Chris H Sep 18 '18 at 16:31
  • But I have no problem with my bike at any speed, just need to shift the assistance level down when I ride slower. – h22 Sep 18 '18 at 16:42
  • I mean you should be able to ride slowly in traffic then accelerate with maximum assistance without the need to change modes just when you might want to change gear as well. This is typical commuting conditions round here, and what a lot of people buy ebikes for – Chris H Sep 18 '18 at 19:20
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From a maintenance and longevity point of view it's probably not the best idea. Using more assistance puts more strain on the battery and motor. This will cause those parts to wear out quicker.

Also, the bicycle's drive train itself may suffer unnecessary wear. When starting from a stop, it's much easier on the bike (chain, sprockets, chainrings, spokes , etc) to put the bike in an easy gear and use the mechanical advantage of the gears to start yourself off without putting too much power through the drive train. However with an electric bike, it's all too easy to leave the bike in a harder gear and let the motor do a lot of work. This puts extra strain on the parts of the bike, causing them to wear out prematurely.

  • Paragraph 2 isn't going to be very true for a hub motor though -- if you are actually lettting the motor do the work, and is more of an argument in favour of changing down. – Chris H Sep 18 '18 at 14:39
  • It will depend on the type of system you are dealing with. I've heard that broken spokes are much more common with hub drive bikes. – Kibbee Sep 18 '18 at 14:46
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    you may even have heard it from me! though the load on the spokes of a rear hub wheel from a standing start is going to depend only on the overall torque after all gearing, or effectively on the acceleration. So if maximum assistance means you accelerate harder, that stresses the spokes more, but if it means you accelerate the same by pedalling more gently, the spokes won't be under more stress (I've always blamed the unsprung mass and big flanges/ bad angles myself -- and badly-built wheels) – Chris H Sep 18 '18 at 15:00
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Higher discharge rate (at higher assitance levels) causes accelerated battery wear (source: figure 4 of this article). That said, if you're discharging below 1C (for example at 250W legal limit on a standard 360Wh battery), the difference is very small and you shouldn't be concerned.

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