Question about free-wheeling.

Electrically assisted bikes, trikes, etc.
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Question about free-wheeling.

Postby richardhb » 28 Aug 2018, 6:04pm

So I'm on my bike coming up to a hill, can you simply turn off the battery and free wheel, or just pedal slowly. Does that save the battery any, much? I fancy riding it like a bike, but just getting a bit of help now and again. Will the battery take stop and start over and over, or is it best to keep it on low?

Hope you get my drift?


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Re: Question about free-wheeling.

Postby meic » 28 Aug 2018, 6:28pm

Depends on the bike.
Most will just freewheel, some can recharge your battery using the energy of momentum or descent.
However I dont reckon such regeneration will be worth much ever and freewheeling could me more efficient, leaving the energy as momentum. Regeneration will always be a better use of momentum than using brakes but the useful gap between free rolling and needing to use brakes will be elusive.

I am basing this on a pessimistic real life figure for the efficiency of regeneration and possible charging rates.
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Re: Question about free-wheeling.

Postby brynpoeth » 28 Aug 2018, 6:34pm

If trains can do it, so can bikes
Braking going down a steep hill destroys a lot of momentum/energy, it must be possible to store it in the battery
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Re: Question about free-wheeling.

Postby stodd » 28 Aug 2018, 6:41pm

As mentioned, almost all will just freewheel.
They won't be using anything significant from the system, so turning it off won't help conserve energy/save battery.

I don't think turning off/on stop/start will harm the battery; just something else to worry about to no good end.

p.s. after extra post
@brynpoeth Bikes can be made to regenerate, but the complications of the system make it heavier, more expensive and less reliable.
As @meic mentioned, deciding when to regenerate is a fine balance.
Conventional wisdom is that it isn't worth it; but of course conventional wisdom can be wrong, and design advances may change the trade-off some time in the future.

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Re: Question about free-wheeling.

Postby kwackers » 28 Aug 2018, 8:56pm

brynpoeth wrote:If trains can do it, so can bikes
Braking going down a steep hill destroys a lot of momentum/energy, it must be possible to store it in the battery

The maths is straightforward, the amount of energy is next to worthless, 95% of all the energy you use is taken fighting the wind.

If you had several miles of downhill then it'd provide a useful few percent but it's not often you get several miles of downhill...

Where it would score, is rather than using gravity to wear out your brakes, wheels and cause things to overheat you could simply store that energy in the battery safely instead. Might not be worth much, but it's better spent charging the battery than wearing the bike out!