0-15mph acceleration of 250W electric bicycle?

How long does it take a 250W electric bicycle to accelerate from 0-15mph without pedal assistance?

 

How fast do they go uphill?

"How long does it take a 250W electric bicycle to accelerate from 0-15mph without pedal assistance?"

 

A very long time (clue pedelec ;-)

 

"How fast do they go uphill?"

 

Depends on a number of factors, Cranks drive or hub and type of, and gradient of hill. But somewhere between a few mph to 15 odd mph.

Depends:

On what motor

How heavy you are

The bike

It's a bit of an open question to be honest. Accelerating from a stand to top speed without peddalling is the best way to eat your battery.

Why do you ask?

With a sim fit man they zip off like a rocket and climb at 15 mph.

With an old fat asthmatic they still go not badly and climb reasonably well.

Of corse the steepness of hill etc all count too.

Oh the 250 watt is a fudge most legal motors can max at over 600 watts some can hit a Kw and gearing helps too.

A 500watt direct drive can struggle on a fairly simple hill as no gears and it really won't do 750 watts or it would be sold as such.

How long does it take a 250W electric bicycle to accelerate from 0-15mph without pedal assistance?

 

How fast do they go uphill?

 

Very few ebikes have throttles.

 

Mine goes no where if you do not pedal

 

Up hill, very fast or very slow

Lets estimate:

The average torque of a 250w motor below 15 mph would be about 24NM. You can get that from the Ebike.ca simulator.

 

The radius of a 26" wheel is about 30cm, so the force at the tyre would be 24/.3 , which is 80N.

 

Acceleration is force divided by mass. Lets say a 75kg rider on a 25kg bike, so 100kg total. That means that the acceleration is 80/100 = 0.8 M/S/S

 

The first equation of motion says that final velocity = initial velocity +acceleration x time or V=U +AT. Turning that around, you get V-U=AT or T=(V-U)/A

 

U is 0, V is 15mph, which is 15x1500/ 60/60 M/S = 6.25 M/S

 

Therefore we have T = (6.25-0)/ 0.8. which is 7.8 seconds.

QED.

that seems to be too long. I reckon it takes less than 12 seconds to hit 15mph.

Acceleration is force divided by mass. Lets say a 75kg rider on a 25kg bike, so 100kg total, which is roughly 1000N. That means that the acceleration is 80/1000 = 0.08 M/S/S

.

 

Should it be 80/100(kg) giving 7.8 seconds

With pedaling (I only have a pedelec to test with) under 4-5 seconds, I don't ride with a clock so that is from counting in my head. Healthy, reasonably fit 78 kg slightly asthmatic 61 year old man on +25 kg bike.

 

I have stopped riding up hills at 25 km/h in order to save the battery and go further so now I am at between 16 and 19 km/h in assistance level 3.

Lets estimate:

The average torque of a 250w motor below 15 mph would be about 24NM. You can get that from the Ebike.ca simulator.

 

The radius of a 26" wheel is about 30cm, so the force at the tyre would be 24/.3 , which is 80N.

 

Acceleration is force divided by mass. Lets say a 75kg rider on a 25kg bike, so 100kg total, which is roughly 1000N. That means that the acceleration is 80/1000 = 0.08 M/S/S

 

The first equation of motion says that final velocity = initial velocity +acceleration x time or V=U +AT. Turning that around, you get V-U=AT or T=(V-U)/A

 

U is 0, V is 15mph, which is 15x1500/ 60/60 M/S = 6.25 M/S

 

Therefore we have T = (6.25-0)/ 0.08. which is 78 seconds.

QED.

Calculations like that at 1am, that's incredible.

Should it be 80/100(kg) giving 7.8 seconds

 

What's one decimal place among friends?

 

It's Christmas 0.78, 7.8 or 780 very well done.

Yes, it was late. I got my units mixed up like any schoolkid. The units of mass are kg not N, so it's out by a factor of 10. The correct answer is about 7.8 seconds. I edited the one above now.

 

It would be interesting to have a race between a hub-motor and crank-motor with exacly the same controller. Which one would win and why? That's your homework for tonight.

Well I'm impressed. But then I get confused working out the various machine ofsets for a mortice and tenon.

How long does it take a 250W electric bicycle to accelerate from 0-15mph without pedal assistance?

 

How fast do they go uphill?

Not being funny, I hope, but get on one and find out. That would be my best suggestion for your best answer.

Not being funny, I hope, but get on one and find out. That would be my best suggestion for your best answer.

Not being funny, but it's freezing cold outside...so I'm not going anywhere. Besides, we all know it's 7.8 seconds now!

Besides, we all know it's 7.8 seconds now!

 

They vary due to a number of factors, mine is faster than that.

 

Reasons: My 65 kilos, bike has controller capable of delivering over 28 Amps, rear hub motor is in 20" wheel.

.

Uphill speeds depend on the motors winding, and the amps allowed by the controller,also battery voltage,same bike same hill same motor at 48 v with 30amp controller i can do 11mph with a bit of help,48v with 10amp controller and its down to about 7mph with a lot of help,and it feels like hard work,36v with a 18amp controller about 9mph with a little help,same on the flat more volts and more amps accelerate much quicker,but drain the battery far quicker,this is on a hill that most lycras get out of the saddle for, and a lot of people get off and push.

Yes, it was late. I got my units mixed up like any schoolkid. The units of mass are kg not N, so it's out by a factor of 10. The correct answer is about 7.8 seconds. I edited the one above now.

 

It would be interesting to have a race between a hub-motor and crank-motor with exacly the same controller. Which one would win and why? That's your homework for tonight.

Im going for the hub motor on all but the steper hills, when the crank motor can start in a lower gear and gradually build up speed through the gears.

Very few ebikes have throttles.

 

Is that correct?

My impression is that actually out there in the world, the bulk of bikes are Chinese and do have throttles.

Both of mine have.

Is that correct?

My impression is that actually out there in the world, the bulk of bikes are Chinese and do have throttles.

Both of mine have.

I have 8 ebikes at the moment. They all have throttles. My neighbour has two, and they both have throttles as well. In fact, I'm pretty sure that every ebike I've ever seen out and about in Telford (at least 100) had throttles except two Kalkhoffs.

 

It's rare to see an ebike in a shop now with a throttle, but many seem to grow one not long after they left the showroom.

I have never seen a pedelec with a throttle. I have seen an illegal Chinese e-bike (1 kW motor) with a throttle, once, never saw it again despite it being in a tower block in my GFs immediate vicinity.

I have never seen a pedelec with a throttle.

 

Other than a Stealth bomber, I haven't seen any around here either

 

I guess that either the water here is healthier to drink than it is in Telford, the people less decrepit, or just aren't so lazy.

Edited December 28, 20169 yr by EddiePJ

Other than a Stealth bomber, I haven't seen any around here either

 

I guess that either the water here is healthier to drink than it is in Telford, the people less decrepit, or just aren't so lazy.

I think it's more to do with affluence. Telford is a town full of poor people.

How long does it take a 250W electric bicycle to accelerate from 0-15mph without pedal assistance?

 

How fast do they go uphill?

 

 

Plenty of places at the Black Mountain Cycle Centre where a emtb will accelerate from 0-15mph in under 1 second without pedal assistance!

Leaving aside terrain and the like, I should have added that if I had to pick a hub drive or a crank drive bike to complete this challenge, then for me it would be hub drive every time.

 

That opinion is based purely on my experience of running both systems, that with a hub drive bike, the transition from zero to motion and increasing speed, is more fluid. With a hub drive bike, the gear changes always seem smoother with more precision. Having said that, the Pro Connect that I recently rode that had a Panasonic motor, was seemingly very smooth, quiet and nice to use.

 

If both bikes were fitted with single speed identical final drive gearing, I would have no idea which would be quickest, but I still think that I'd opt for the hub drive bike.