Wind And EBike Range

[HombreNeuvoElectro]

Hi All,

A topic that i would like to discuss with some of the forum members is how wind effects the range of an ebike drastically.

My commute involves an inward commute generally with the direction of the wind and an outward commute generally against the wind. Before i constructed my ebike I used the great simulator on ebikes.ca to estimate my range and i wanted a range of 30 miles and 25mph travel speed. What i have come to realise is that far more than hills, weight, pedal effort etc. the wind speed affects my range a lot.

The simulator does not give the option to incorporate wind speed.

For example travel generally with the wind of 25 kph at 20moh the Cycle Analyst indicates that i would be pulling about 9amps from my 52V 20Ah battery pack. So this would give a decent range. However travelling into and 25kph wind with hard pedalling the cycle analyst shows i am pulling up to 16amps travelling at the same speed. So in reality i do not have a 30mile guaranteed range with my 20Ah pack.

25kph wind is not very strong wind and i would not like to imagine how my range would plummet to travel at the same speed into a strong wind.

I think i would need 30Ah of battery to travel 30mile guaranteed at this speed.

Has anyone else found that wind affects energy usage more than anything?

So things like:
1. Bike Weight
2. Rider Weight
3. Tyres
4. Pedal effort

I would be interested to know if some other board members agree with this or have found different.

Maybe some stats in this thread to help out newbies planning an ebike?

It was one thing that i did not pay too much attention to in planning my bike

 

[itchynackers]

I've found the "evcalc" software to be the most accurate predictor (sorry other software guys). I used it to plan my Pikes Peak run and it was very close. It also lets you enter windspeeds. Not sure where to find it anymore. Maybe a search will turn it up.

 

[dogman dan]

Totally agree!

This is why my rule of thumb for battery sizing is so conservative. At 36v, traveling 20-25 mph, 1 ah = 1 mile. Hell yeah you have a lot more range than that, but only on truly flat ground, with no wind, or you pedal hard, or you slow down.

Come winter, my 15 mile commute home becomes not only uphill, not only with a cool battery that is sluggish, but now it's into about 10-15 mph of breeze because the wind blows the other way seasonaly. In winter, I've learned not to exceed 20 mph at all if I want to make it. A 25% recuction in range or more depending on the wind. I lose 10% of that for a battery at 50F. The rest is headwind. The hill doesn't change, but if wind slows you as you climb it, you get even more into the inefficient rpm's. I gotta pedal hard up that hill in winter. Summer I just fly up it.

Bottom line, you have a range at a certain speed, say it's 25 mph and your range is 20 miles. Add 10 mph of wind, and now to get that 20 miles you better slow up by about the same as the wind speed. This affects you all the more if you have a bike loaded with wind catching panniers, your winter coat flaps, your handlebars are tall etc. Slick and tucked, you can get away with much more of course.


On the other subjects, some have an effect, but nothing you need worry about if you have sized your battery right. Tire pressure and tread matter, but not hugely when you crank the difference into an equation starting at 1000w. So what if you shave 20w?

Weight is another story. It does slow you down even on the flat, but when weight reallllly matters is up a hill. That's 10 grade physics. Lift more weight takes more watts. Too much weight up too much hill, you slow down to the smoke your motor rpms again. On the flat, it takes 50 pounds to start really noticing weight affecting range. By that I mean, 50 pounds of cargo you don't normaly carry. I'm assuming your ebike has 30 pounds in the motor and battery.

Pedaling matters. But how much depends on the % of the total wattage it is. If you pedal 100w continuously for 20 miles, which is pretty good for average old fart, that might be 33% of 300w, or 3.3% of 3000 w. However, if stalled at 3000w, your pedal in the right gear might get you from making 100% of your 3000w into heat, and into only making 80% of it into heat. :lol: Debatable if worth it, but when I stall it below 5 mph, I start pedaling like hell hoping it helps. A few hundered feet of this will be too much though, and time to get off and push perhaps.

A more common example, Emory Pass in southern NM is about 10 miles of 8-10%. Riding up it part throttle, while pedaling 100W or so to get up it at not less than 15 mph works great. You can do miles of steep hill that way, the idea being to try to keep your watts no more than 800w or so going up the long steep hill. The 100w seems insignificant, but what is not insignificant is that you keep the speed up enough to make less of that 800w into heat. That is where your 100w of pedaling can translate into 500w more to the wheel.

 

[adrian_sm]

Bike weight and rider weight, will increase rolling resistance linearly, but probably have a bigger impact on the energy used to accelerate you up to speed. This low speed torque is where the motor is the most inefficient at turning input power to output power, so lots of stop, full throttle, start riding can really kill your range.

Once you are up to speed wind drag is pretty much where all your energy is going, far outweighing rolling resistance, and other losses. And the power required goes up at a cube rate.
So travelling at 30kph + 25kph headwind will take very similar power levels as travelling at 55kph.

Here is a random graph showing the comparison of rolling resistance to aero drag for various speeds.

 

[dogman dan]

Yeah forgot to mention that while I was adding comments about weight etc.

Getting more weight going definitely takes more energy. Again 10th grade physics if you remember 10th grade. You really see that with my longtail, which exceeds 100 pounds bike and one battery. It pulls a lot more time at max wattage to get to 20 mph than a bike weighing 30 pounds less. Now that I put a 5304 on it, it really pulls that power longer working up to 30 mph.

 

[Ypedal]

Wind is the primary reason i got into ebikes in the first place.

I live in a fairly flat area of the world, some hills but nothing major... but here in the maritimes, wind, is cyclist enemy no.1 .. and on my way home i've seen it bad enough to draw 1500w + on flat land going 40 kph... leaning in..

hills are always there.. but wind just happens.

Keep tires inflated at 40 psi +

 

[The fingers]

I usually slow down and pedal assist into a headwind to conserve power. :wink:

 

[dogman dan]

Got to if you aren't going to make it any other way.

Spring winds here can be 50 mph in the afternoons. Even crosswinds can kick your butt at that speed. But when I make the turn to climb that hill in the spring, I have that wind right on my ass. Wonderfull ride that last six miles then. Always laugh my ass off when I pass a loaded cross country pedaler going the wrong way on a spring afternoon. Shoulda started from San Diego in the spring dumbass. Or at least stop at noon when the wind gets really cranking.

 

[ebent]

One of several reasons I ride a recumbent. My ca tells me I get 3 plus miles per ah. I like a softer ride and don't fully inflate my schwalbe big apple tires. If I do add pressure my effeciency improves. I peddle but not cray. Enough for an aroebic benefit. Not much more.

 

[Ypedal]

it's call pedal.. pedaling.. not peddle.. geeeez.. :lol:

 

[Miles]

it's call pedal.. pedaling.. not peddle.. geeeez.. :lol:

http://endless-sphere.com/forums/viewtopic.php?p=389054#p389054

 

[cal3thousand]

Yeah, as said here earlier, the wind speed adds an exponential factor on TOP of your current speed.

So a wind speed increase of 25% of your current speed is like 56% increase in force necessary.

25% wind speed at riding speed of 20mph is just 5mph of wind. So if you are going along at 20mph into a 5mph headwind, expect to use 56% more battery power than if you had still air. If you were using 20Wh/mi in the still air, it will now cost you 31.26Wh/mi into the headwind.

Too bad humans can't survive a vacuum situation. Vacuum speed tunnels


PS: This still doesn't mean that wearing spandex is acceptable.

 

[Ypedal]

going 5 kms at 20 kph takex X amount of energy . ( roughly 30wh )

going 5 kms at 40 kph takes more than 2x the energy. ( 45 ~ 60 wh )

going 5 kms at 60 kph takes arpox 1.5ah at 100v = 150wh ( from experience )

it's not only the wind, but the air resistance you must factor in.,.. add heavy headwind to the numbers above and it goes higher.

 

[cal3thousand]

...

it's not only the wind, but the air resistance you must factor in.,.. add heavy headwind to the numbers above and it goes higher.

yup.. that's why the calc requires you to factor in your current speed.

 

[veloman]

Yup, I always take the slower neighborhood route with lots of trees when going into the wind.

Especially with the typical upright ebiker position and casual clothes, you catch a LOT of wind. Nothing aerodynamic about it.

The only thing you can do is lower your speed a bit, lower your position and wear tighter fitting clothing.

 

[ebent]

Because I like to listen to my stereo while riding, wind is an issue for listening. Dead calm about 17 or 18 mph the wind in my ears starts to interfere with hearing. Wind at my back I can go faster to still hear and reverse for wind in my face. My stereo frequently dictates my speed.

 

[cal3thousand]

This reminds me of an idea that I had awhile back about a seating arrangement that would easily allow a slight aero-tuck while at non-pedaling speeds.

My idea consisted of a seat that could tilt with a lever, pegs for your legs and adapted bars. Kind of like a bike that can be upright like a touring moto, but then change to a rocket bike type arrangement.

 

[Pat Eaton]

A yes wind.... I find up to 30% more energy required to battle winds on my commute. I travel 36 km each way and the ride home is always into a headwind. My ah usage goes up by as much as 30% on the way home. I ride a recumbent and am building a delta velomobile, with the desire to beat the wind. So far it has worked, but the rolling resistance of the trike kills any advantage.

I am buying a higher voltage battery to beat the wind.

 

[amberwolf]

A topic that i would like to discuss with some of the forum members is how wind effects the range of an ebike drastically.

Think of headwind as if you were riding that much faster; that's the energy usage you would have to calculate for.

Meaning if you always have a 5MPH headwind, and you are always riding at 20MPH, in reality your power usage will be that of 25MPH.

Calculate your stuff out to deal with that possibility (or probability, in some places that always have certain winds at various places and times of day), and you shouldn't have too much worry, especially if you add a fudgefactor on top of that of some percentage for worse days.



FWIW, that is part of the consideration I made when choosing semi-recumbent over saddle or upright seating; it helps with aero in wind a little bit. Not a lot because of the poor aero of the rest of the bike, with huge boxes on it, but it helps at least mitigate some of that aero loss.