Impact of rider weight on range

[RobF]

I wonder what impact rider weight has on the range of en ebike?

Put another way, how far would the bike go with a notional weightless rider?

The type of bike doesn't really matter, seems to me all the legal ones give about the same range, give or take.

My experience is with Bosch, and I can get about 40 miles from an 11ah battery on tour setting in average to easy conditions.

How much further would I go if I did as the doctor would like and lost some timber?

I also wonder what amount of weight would make a difference.

Seems to me unlikely a kilo or two would alter the range, but several kilos - or a couple of stones - would.

 

[Woosh]

if you use the tool at ebikes.ca, you can get an idea of the effect of weight on battery consumption. Set the gradient to 2% to represent roughly urban conditions. That figure needs only to be something more than zero.
The load plot shows 295W at 15mph.
If you change the weight (rider + bike) from 100kgs to 80kgs, the same load plot shows 254W at 15mph.
You can see that the consumption if roughly proportional to the rider's weight.

 

[Gubbins]

With loss of weight will come an increase in fitness so gains will be twofold

 

[Nealh]

9.9 wh Rob which I think is fairly normal for a fit/regular rider.
My 11ah battery can get me 38 miles in level 1 (eco mode)with my oxydrive kit Boardman 700c, my weight ranges 80-86kg plus an extra battery and panniers.
In level 3 (turbo) this week in windy conditions I did 26 miles and changed the battery over as I had to ascend in to Cuckfield and new the LVC would cut in.

 

[kangooroo]

On a completely non-technical level, I am 53kg and my husband is about 90kg.

On the same hilly ride on the same bike at the same speed in the same weather conditions, I can gain 24 miles from an 8.8Ah battery and he manages 18 miles. He is a muscular build and possibly contributes more pedal power than I can but other variables are (more or less) the same.

 

[Gubbins]

Yesterday I met an 20 stone ex rugby player who had just bought an a bosch/Cube emtb to loos weight. I should have asked him about range...

 

[RobF]

View attachment 18726

if you use the tool at ebikes.ca, you can get an idea of the effect of weight on battery consumption. Set the gradient to 2% to represent roughly urban conditions. That figure needs only to be something more than zero.
The load plot shows 295W at 15mph.
If you change the weight (rider + bike) from 100kgs to 80kgs, the same load plot shows 254W at 15mph.
You can see that the consumption if roughly proportional to the rider's weight.

The site seems to suggest a 10 per cent reduction in weight equals a 10 per cent reduction in power consumption.

Is it that simple - and linear?

Perhaps it is.

And does 10 per cent less power to push you along equal 10 per cent more range from the battery?

 

[Artstu]

 

[Woosh]

The site seems to suggest a 10 per cent reduction in weight equals a 10 per cent reduction in power consumption.

Is it that simple - and linear?

Perhaps it is.

You need to do a finite element analysis to refine the estimates, but yes, for our purpose, it is linear.

And does 10 per cent less power to push you along equal 10 per cent more range from the battery?

For our purpose, it is. In practice, the tool lets you input the battery and controller internal resistance to get a more accurate result.

 

[Nealh]

On a completely non-technical level, I am 53kg and my husband is about 90kg.

On the same hilly ride on the same bike at the same speed in the same weather conditions, I can gain 24 miles from an 8.8Ah battery and he manages 18 miles. He is a muscular build and possibly contributes more pedal power than I can but other variables are (more or less) the same.

In this case hubby is 70% heavier and loses 25% range, a lighter rider with less watt input can perform better due to less effort needed to propel the same bike.
Using a chart/calculator can only give a rough guestimate due to the many variables involved and should be used with a pinch of salt.

 

[RobF]

On a completely non-technical level, I am 53kg and my husband is about 90kg.

On the same hilly ride on the same bike at the same speed in the same weather conditions, I can gain 24 miles from an 8.8Ah battery and he manages 18 miles. He is a muscular build and possibly contributes more pedal power than I can but other variables are (more or less) the same.

Those extra six miles don't sound a lot, but do equate to 25 per cent extra range, although that's for close to half the rider weight.

 

[Woosh]

I bet they don't run the bikes to empty.
Their experience confirms that weight matters, the heavier you are, the bigger battery you need.

 

[Artstu]

I bet they don't run the bikes to empty.
Their experience confirms that weight matters, the heavier you are, the bigger battery you need.

Rider input makes just as much difference I reckon, on the flat I imagine rider weight makes hardly any difference.

 

[Wander]

I wonder what impact rider weight has on the range of en ebike?

Bosch's range assistant page let's you put Total weight in as one of the parameters.

 

[Deleted member 4366]

Weight makes very little difference to range unless you have hills. Most people can pedal a bike at 10 - 12mph on the flat without any assistance, so range would be infinite.

As far as hills are concerned, power consumption is directly proportional to weight if the speed is the same, so, all other things being equal, on a 20kg bike, a 100kg rider would use 71.4% more battery than a 50kg rider, or he can go 58% of the distance. That only applies while going uphill, so if half the journey were flat or downhill, the difference would drop to 29%.

That doesn't take into consideration that a heavier rider might be able to pedal harder, but if he's heavy because he's unfit, he might not be able to pedal as hard as a fit 50kg rider.

There's no question that rider weight makes a massive difference to ebike performance. Even 10kg difference is very noticeable. You can easily test that with a rucksack and 10kg of bricks or dirt in it. Then try 20kg or 30kg, then you can see what some of us are up against. If you're heavy and you want to test what it's like being a lighter rider, you have a few choices: cut off an arm, liposuction (don't try sucking a battery. It doesn't work - I tried it) or starve yourself for three months.

 

[Woosh]

Weight makes very little difference to range unless you have hills. Most people can pedal a bike at 10 - 12mph on the flat without any assistance, so range would be infinite.

Roads are rarely totally flat, adding to that, you have stops and starts.
The end result is that you can approximate urban riding to a road with 1%-2% gradient to account for these additional energy losses.
Wind resistance accounts for a large part of energy requirement, tyre friction adds maybe 5%-10% at below legal speed. When you consider that a heavy rider is usually a large rider, a larger person has a larger cross-section facing the wind, it follows that wind resistance grows with weight.

 

[Artstu]

I bet Philip used a fair bit of power on this ride last year, just waiting to see if anyone went faster today.

https://www.strava.com/activities/527082704#12680908719

 

[Croxden]

I thought my range was reducing but could be my weight increasing.

So my trousers have not shrunk in the wash after all.

 

[Cliff-C]

Responses demonstrate that the debate is all rather academic. There are too many variables to calculate statistical impacts of rider weight that are meaningful to an individual. In addition to rider and bike weight, there are wind resistance caused by rider position, bulk, clothing and weather; fitness; terrain; motor type; battery type, age and condition; tyres; average speed; etc. If your bike's range isn't enough consider improving fitness or getting a bigger battery. As D8veh says, rider weight on hill does make a significant difference but are we prepared to lose 10kg for a bit of extra range?

Sent from my Paris using Tapatalk

 

[Deleted member 4366]

As D8veh says, rider weight on hill does make a significant difference but are we prepared to lose 10kg for a bit of extra range?

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It's not a bit of extra range, though. When I'm below 90kg, I can ride my road bike, which means no more battery anxiety. I've another two weeks to go since my weight ballooned to 105kg at Xmas. Presently 91.6kg. Boy, can I tell the difference.

Last Monday, I was really lucky. We took my mum out for a cream tea at a posh hotel. They gave us deluxe sandwiches and loads of nice cakes, so I pigged out. The luck was in getting food poisoning from it, so I puked the whole lot up the next day and lost 2kg in a single day.