Electric Bike, Power, Relative Overall Efficiency

Electrically assisted bikes, trikes, etc. that are legal in the UK
hemo
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Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Electric Bike, Power, Relative Overall Efficiency

Post by hemo »

If not towing a trailer my typical wh/m rate is 8 -10 with my hub motor bikes.
UpWrong
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Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: Electric Bike, Power, Relative Overall Efficiency

Post by UpWrong »

So around 500 Wh is taking me 50 miles in 4 hrs. So 10 Wh per mile, but that is with me contributing some of the power. I'd guess it's more motor than me in a ratio of 2:1. I which case the motor uses are 15 Wh per mile without assistance from me.
Bonzo Banana
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Joined: 5 Feb 2017, 11:58am

Re: Electric Bike, Power, Relative Overall Efficiency

Post by Bonzo Banana »

UpWrong wrote: 13 Jun 2022, 4:36pm
Bonzo Banana wrote: 17 May 2022, 6:50am I think the common term used is watt hours per kilometre and the lowest I've seen was 6Wh/Km which was a small geared hub motor with the clutch disabled and regen enabled. I guess the average figure is around 10 Wh/Km. There is a basic rule that you divide the battery capacity by 10 to give the rough guide to distance in kilometres. So if you have a 600Wh battery you can expect around 60km of range or around 40 miles. It should be pointed out hub motors are separated into two types direct drive and geared. The efficiency between all 3 motor systems is actually very comparable with a lot of overlap its all down to implementation really and how you ride.
So 10Wh/km, or 16Wh/mile for an electric bike. The best electric cars are around 250Wh/mile, so an electric bike is about 15 times more efficient than an electric car. Food for thought.
I didn't know electric cars started at around 250Wh per mile but when you think about it the difference in weight between a bike and a car is perhaps around 15x very roughly. However there is nothing in the car that assists except for regen braking I suppose. It feels like efficiency is similar when you factor in weight. Cars are much, much more aerodynamic though.

We really need to legislate for smaller cars, driving around with 1.5 tons of metal around you is so wrong for the environment and bad for wear and tear of the roads. It's also more dangerous to other road users due to size and force of impact.
Jdsk
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Joined: 5 Mar 2019, 5:42pm

Re: Electric Bike, Power, Relative Overall Efficiency

Post by Jdsk »

Bonzo Banana wrote: 26 Jun 2022, 10:12amCars are much, much more aerodynamic though.
Lower drag coefficient, higher frontal area.

Jonathan
Biospace
Posts: 2008
Joined: 24 Jun 2019, 12:23pm

Re: Electric Bike, Power, Relative Overall Efficiency

Post by Biospace »

Cugel wrote: 18 May 2022, 11:07am
Front hubs have the reputation of interfering adversely with the handling of a bike. They also seem to come with batteries that have to be hung or otherwise clagged to the bike externally, often high up so that handling is further degraded by raising the bikes centre of gravity. But they're easy to fit. The wheel can be got out without too much extra bother - although you can't swap to a different wheelset without including another hub motor.

Rear hubs are unobtrusive and are said to give a better feel in that their "push" is identical in placement (the rear tyre) to the push from the pedalling rider, unlike a front hub. But wheel change and puncture mending gets rather involved. They also tend to have a smallish torque (40Nm rather than 60 or 80).

There are several varieties of mid-motor. They can often improve handling by lowering the centre of gravity and most (not all) come with a frame-hidden battery. Your remark that you have " ....even less wish to push power through chains, sprockets and hub gears that weren’t built with that in mind" ignores the fact that the chains, sprockets and hub gears were designed precisely to handle power put through them. Many fit cyclists can put a continuous 200 - 250 watts through their gearing and those racing fellows can put up to 1400 watts momentarily through the transmission during a professional race sprint! Good time trialists often generate a continuous 300 or more watts for hours at a time.


Cugel, trying to remain motor-unseduced.

I was aware of this reputation before trying my first ebike which was front drive and with a carrier mounted battery at the back, but completely stable (26" Raleigh). It pulled like stink from rest, yet the front wheel never began to feel wayward, even through greasy corners. Quite the opposite with a Giant, which also had the battery at the back, but as a side-mounted pannier. It had a rear hub motor and you had to watch the power through corners wherever the surface wasn't perfect, a combination of a lot of power going through one tiny contact patch and a centre of mass a long way back. The tyres were good quality. Lovely bike, otherwise.

The third ebike had a mid-mounted motor which introduced some vibration to the frame, which I hated, as well as much more noise than a near-silent hub motor (amplified by the frame). I imagine a £4000 ebike doesn't suffer from either of these issues. Of course a chain and its cogs will withstand a huge load through them, the matter is more of longevity. It was a tedious expense to have to replace these items three or four times more often than on my normal bikes, made all the worse because there were none of the expected benefits of having a geared motor.

My findings were that front drive was more stable, better balanced and with better traction, especially off-road and through fast corners.
Biospace
Posts: 2008
Joined: 24 Jun 2019, 12:23pm

Re: Electric Bike, Power, Relative Overall Efficiency

Post by Biospace »

Bonzo Banana wrote: 26 Jun 2022, 10:12am We really need to legislate for smaller cars, driving around with 1.5 tons of metal around you is so wrong for the environment and bad for wear and tear of the roads. It's also more dangerous to other road users due to size and force of impact.
This cannot be repeated often enough.

Mass is the key to less harm wrt motor vehicles, but it's the most expensive to engineer in. So we have family cars approaching 200hp weighing nearly 2 tonnes. It's utter lunacy, yet the government continues to give even heavier 4x4s tax breaks.
Manc33
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Joined: 25 Apr 2015, 9:37pm

Re: Electric Bike, Power, Relative Overall Efficiency

Post by Manc33 »

I reckon mine's using 17 Wh per mile on power level 3 (of 5).

That's from a 42 mile ride that included going up Winnats Pass.

The battery went from 100% to 37% (54.6v to 45.0v). Average speed was 14.74 MPH.

My bike is about 60 lbs and I'm about 190 lbs, probably putting in 50W-80W myself.

Once the battery gets down under 40% it's basically running on fumes. Any steep hill will have it dropping under 20%.

Once it's down to 25% then it's as good as depleted and will start going to levels like 3% up the first steep hill.
We'll always be together, together on electric bikes.
Carlton green
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Joined: 22 Jun 2019, 12:27pm

Re: Electric Bike, Power, Relative Overall Efficiency

Post by Carlton green »

We really need to legislate for smaller cars, driving around with 1.5 tons of metal around you is so wrong for the environment and bad for wear and tear of the roads. It's also more dangerous to other road users due to size and force of impact.
I couldn’t agree more with that sentiment and have been saying similar here for a long time. Of course this is a bit of thread drift, but still a very valid point to make.
Don’t fret, it’s OK to: ride a simple old bike; ride slowly, walk, rest and admire the view; ride off-road; ride in your raincoat; ride by yourself; ride in the dark; and ride one hundred yards or one hundred miles. Your bike and your choices to suit you.
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