Extreme efficiency?

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recumpence   100 GW

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Extreme efficiency?

Post by recumpence » Oct 18 2008 4:13pm

Does anyone know of any records regarding E-bike efficiency (WH per mile at whatever speed)?

I am curious. I heard alot of numbers thrown around. I would love to see how far the technology has been pushed in the area of efficiency.

Matt
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Re: Extreme efficiency?

Post by voicecoils » Oct 18 2008 4:33pm

I think ebikes are not the place to look for efficiency records for EVs in general, but there might be a chance to set your own record :)

To places to find VERY efficient electric vehicles:

Solar car racing:
http://www.wsc.org.au/
http://www.americansolarchallenge.org/

Electrathon racing:
http://www.electrathonamerica.org/

I know many solar cars use the CSIRO wheel motor, a 1.8kW 98% efficient brushless design. Costs $13k and you still have to design the wheel to put it in. :shock: All you get is two rotor rings and a laminated stator! See here: http://www.csiro.au/resources/pf11g.html

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Re: Extreme efficiency?

Post by recumpence » Oct 18 2008 5:12pm

I am not trying to set any records. I am curious more than anything.

I would love, however, to push my own efficiency as far as I possibly can. For me, the best efficiency I have ever achieved without any pedalling what-so-ever, is 13.4WH per mile at 18 miles per hour. I have heard numbers from guys here on the forum, of 15wh per mile at 20 miles per hour (roughly what my bike will do), I have heard 26wh per mile at 26mph. I have heard 9wh per mile at 10mph. etc.

I know my bike wastes alot of power just to spin the wheel. My bike draws 400 watts to free spin the rear wheel at 44mph. So, at 20mph, the bike wastes 180 watts. At 20mph, my bike requires under 500 watts roughly 470 to 480 watts (on the flat with no wind). So, that would be roughly 300 watts going to forward speed, and 180 watts wasted through the drivetrain. On top of that, I know my motor is only about 80 to 84% efficient. The controller loses a bit too. Sho, when all is said and done, I should be able to achieve about 9wh per mile at 18mph if I can get rid of the wasted drivetrain drag. Then there is aero. Hmm, I know I could do about 10% better on that.

Basically, it looks like about 6 or 7wh per mile would be the absolute limit for efficiency at 20mph if I am doing the math (and shoot from the hip estimations) correct.

Of course, one could always buy more AH and not worry about it! :wink:

Matt
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Re: Extreme efficiency?

Post by etard » Oct 18 2008 10:05pm

I would start with the most efficient recumbant, (Matt, you should know this), then find one of the most efficient RC motors. You spent, what, $800 for the Plattenburg? What motor would be more efficient at 20MPH? I think that we should set some parameters and 20 mph should be the benchmark cuz that is a standard speed limit. With a less powerful motor and a not-so robust drivetrain, how much better kw/h could you get?
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Re: Extreme efficiency?

Post by swbluto » Oct 19 2008 12:28am

etard wrote:I would start with the most efficient recumbant, (Matt, you should know this), then find one of the most efficient RC motors. You spent, what, $800 for the Plattenburg? What motor would be more efficient at 20MPH? I think that we should set some parameters and 20 mph should be the benchmark cuz that is a standard speed limit. With a less powerful motor and a not-so robust drivetrain, how much better kw/h could you get?
Wait... there's a speed limit? :wink:

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Re: Extreme efficiency?

Post by paultrafalgar » Oct 19 2008 4:22am

voicecoils wrote:I think ebikes are not the place to look for efficiency records for EVs in general, but there might be a chance to set your own record :)

To places to find VERY efficient electric vehicles:

Solar car racing:
http://www.wsc.org.au/
http://www.americansolarchallenge.org/

Electrathon racing:
http://www.electrathonamerica.org/

I know many solar cars use the CSIRO wheel motor, a 1.8kW 98% efficient brushless design. Costs $13k and you still have to design the wheel to put it in. :shock: All you get is two rotor rings and a laminated stator! See here: http://www.csiro.au/resources/pf11g.html
Interestingly, your http://www.electrathonamerica.org/ link leads to http://evworld.com/article.cfm?storyid=1132 where it says that:
"Each car broke the existing record by covering more than 50 miles in one hour using less than a kilowatt/hour of electricity"
I make that 20 watt hours per mile. I think both Matt's and Miles' bikes do better than that? So I disagree with your original statement that "ebikes are not the place to look for efficiency records for EVs". Correct me if I'm wrong.
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Re: Extreme efficiency?

Post by Ben » Oct 19 2008 4:40am

Well the best efficiency from that link equates to 18 watt-hours per mile at an average of 53.16mph.

Matt's bike uses the equivalent of 9 watt-hours per mile just to spin the wheel at 44mph.

I think the electrathon racers are more efficient.

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Re: Extreme efficiency?

Post by paultrafalgar » Oct 19 2008 6:07am

Further up the page Matt says: "15wh per mile at 20 miles per hour (roughly what my bike will do)". So how can that be less efficient!? Unless we're taking in to account the speed. I understood we were talking about absolute efficiency, not speed related efficiency? The real importance of efficiency is not to do with going around a track at 50mph, it's about getting from A to B at a realistic speed (20mph say) in a way that uses the least power, n'est-ce pas?
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Re: Extreme efficiency?

Post by Drunkskunk » Oct 19 2008 10:11am

My best efficancy was 11wh at 15mph. I've done it twice, but i can get 14wh at 15mph fairly easily. Jumping to 20mph, my efficancy tanks. i'm lucky to get 25wh

I think it might be fun to see just how efficent one could make an Ebike.
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Re: Extreme efficiency?

Post by recumpence » Oct 19 2008 11:29am

Speed makes a HUGE difference at least without a fairing. My WH per mile dives to 27 to 34wh per mile at 40mph (depending on the road I am on). If I had a fairing, that would be far better.

My drive system is very innefficient. It was designed to be robust. My mootr was not chosen for efficiency, but for power and reliability.

Anyway, I think it is cool to analyze this stuff. I would love to go for extreme efficiency. But, that setup would not be fun to ride. I think alot would have to be sacrificed.

Matt
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Re: Extreme efficiency?

Post by swbluto » Oct 19 2008 11:42am

True. I was first a proponent for "efficiency" as if it was some kind of ultimate ideal, but then I dismissed that goal after upgrading to 48v and having all that power. :mrgreen:

(But, since my "actual battery capacity" is sort of limited, I throttle my usage of the throttle depending on the intended trip distance.)

And, yeah, the amount of energy used per given distance is nearly proportional to the square of speed EVEN if you use a fairing*.

(Wait... math check. E = f*d = v^2*d. E/d = v^2. Ok, that sounds about right then.)

(*At high enough to speeds for a high enough Reynolds number, which the vast majority of >15 mph e bikes are operating at.)

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Re: Extreme efficiency?

Post by Doctorbass » Oct 19 2008 10:02pm

Mine is doing 15Wh/km at 35kph.. the same speed as Justin used to cross Canada.

that's 1.5kWh/100km :mrgreen: or 1cup of gas equivalewnt /100km

at 45mph it's more like 40Wh/km.

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Re: Extreme efficiency?

Post by swbluto » Oct 19 2008 10:17pm

Doctorbass wrote:Mine is doing 15Wh/km at 35kph.. the same speed as Justin used to cross Canada.

that's 1.5kWh/100km :mrgreen: or 1cup of gas equivalewnt /100km

at 45mph it's more like 40Wh/km.

Doc
Are you(or, rather, cycle analyst) including energy lost in the battery? Because, according to my super duper e-bike calculator, you'd actually get ~48 wh/km including energy consumed by the battery due to internal resistance. Anyways, my super-duper e-bike calculator is predicting a 33-40(35.8 to be "exact") amp battery draw rate at a cruising speed of 45 mph on the flat for your set-up at full throttle. Does that sound close to what you see?

Wait.... that assumed at sea level and at 32 degrees Fahrenheit below freezing. Hehe. Ok, at more reasonable specs, it predicts 40wh/km. So, yeah, that sounds about right.

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Re: Extreme efficiency?

Post by Doctorbass » Oct 19 2008 11:05pm

swbluto wrote:
Doctorbass wrote:Mine is doing 15Wh/km at 35kph.. the same speed as Justin used to cross Canada.

that's 1.5kWh/100km :mrgreen: or 1cup of gas equivalewnt /100km

at 45mph it's more like 40Wh/km.

Doc
Are you(or, rather, cycle analyst) including energy lost in the battery? Because, according to my super duper e-bike calculator, you'd actually get ~48 wh/km including energy consumed by the battery due to internal resistance. Anyways, my super-duper e-bike calculator is predicting a 33-40(35.8 to be "exact") amp battery draw rate at a cruising speed of 45 mph on the flat for your set-up at full throttle. Does that sound close to what you see?

Wait.... that assumed at sea level and at 32 degrees Fahrenheit below freezing. Hehe. Ok, at more reasonable specs, it predicts 40wh/km. So, yeah, that sounds about right.
====== AT 40mph !! =====
To answer to your questions, my setup actually have 4 battery pack that each have 0.018ohm of internal resistance measured. so the total at 100V is 0.072ohm. all my wires are 8 and 6 gauges at the total resistance to the controller is less than 0.1ohm. taking account of the parallel pair of IRFB4110 mosfet that drive each phase side, it's 0.002ohm so that's 0.004ohm per phase ao i would say around 0.110ohm total from the battery to the motor winfing. My battery heat generation is like negligible even though if i drive at 5 or 100A. They never heat up until they reach the 95+% SOC whenre their internal resistance increase faster like any li-ion battery.

usually the power needed that i can see on my C-A to run at 40mph is like 2300-2500W sustained. Your calculation about the amp is not exactly what i measure. the voltage at 2500W is like 92V so it'S like 27A.

Dont forget that my motor is more a Voltage powered motor than a current powered motor due to the winding that is different and that have more turn on each phases.

At 46mph the WH increase is +10Wh/km and power is like 3000W... and the motor temp increase faster!!

I would not run it at full throtthe for a long period cause it would reahc the 125 Celsius dangerous limit that i pre-programmed on my temp monitor!,,, and where the Hall sensor begin to worry about their life!!


Under lower speed like 30mph i really think that the 5303 have more advantages than the 5303 or 5302 cause it use les current and more voltage. current induce heat loss and voltage not... that's the same reason why AC power line of many KV are steped up to 100kV+ for better efficiency and less loss!

5305 need volt 5303 need amp... make your conclusions...


But i admit that more Volts involve more BMS conplications, more expensive charger and more SAFETY :lol:

Doc

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Re: Extreme efficiency?

Post by John in CR » Oct 20 2008 2:31am

I am planning a coast to coast ride in February. While it's not on a remotely similar scale to Justin's ride at only 167miles (268km) from the Caribbean to the Pacific, I want to add my own twist, which is to pull it off on a single charge. I will try to time the ride to best take advantage of a 15-20mph trade wind at my back, but I don't want to bank on a tailwind. I also don't want to limit myself to only 20mph, since there's no legal reason to do so, but DocBass's 15 vs 40wh/mile says it all.

My question is how much can some very basic aerodynamic structures improve efficiency at say 30mph with zero wind? I have no interest in a full fairing, especially in the tropical sun here, however, if a small fairing for the front combined with a tailbox-like shape to reduce vacuum forces and turbulence at the rear, then I'm interested. Anyone have a ballpark estimate of how much efficiency can be gained for a 30mph speed with minimal fairing structure? Could it be as much as 20-30% benefit.

John

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Re: Extreme efficiency?

Post by paultrafalgar » Oct 20 2008 3:47am

Does this help?
http://www.kreuzotter.de/english/espeed.htm
Has a tailbox option.
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Re: Extreme efficiency?

Post by John in CR » Oct 20 2008 8:44pm

paultrafalgar wrote:Does this help?
http://www.kreuzotter.de/english/espeed.htm
Has a tailbox option.
Paul,

Yes that will prove to be an extremely useful tool. It also tells me that a tailwind and considering aerodynamics as much as possible will be critical for success if I want to ride faster than 20mph. Once I get a profile of the 2 significant mountains I need to cross, it will also help really fine tune my minimum pack requirements, which I want to exceed by at least 50%. Worst case, barring an unrepairable break down, I can always recharge at the halfway point. With lots of pedaling up the mountains, I'm pretty confident that packs that will put out 500W continuous for 8 hours (a real 4kwh of capacity) will be sufficient. The first 65miles is almost dead flat and straight with the trade wind at my back, so I may even pack an extra kwh or so of heavier chemistry batteries for that first leg. Run them dry first and unload them to the support car before tackling the first mountain. That seems a lot more legit that a drafting strategy, which would also permit higher speed.

John

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Re: Extreme efficiency?

Post by Link » Oct 21 2008 4:35pm

I used 0Wh/mi out of my battery before I put the motor on my bike.
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Re: Extreme efficiency?

Post by nomad85 » Oct 21 2008 10:36pm

I got 12 wh per mile at 20mph a few times with minimal pedaling, but I have a different tire now, and its not quite as efficient, puncture proof though... I usually get about 25-27 wh per mile at 27-30 mph(full throttle)
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Re: Extreme efficiency?

Post by mi7d1 » Nov 02 2008 8:11pm

recumpence wrote:I am not trying to set any records. I am curious more than anything.

I would love, however, to push my own efficiency as far as I possibly can. For me, the best efficiency I have ever achieved without any pedalling what-so-ever, is 13.4WH per mile at 18 miles per hour. I have heard numbers from guys here on the forum, of 15wh per mile at 20 miles per hour (roughly what my bike will do), I have heard 26wh per mile at 26mph. I have heard 9wh per mile at 10mph. etc.
<snip>
Matt
14.12Wh/mi at 31.1 mph avg is what I did last year at the ePower Challenge in Portland, Oregon. I was the second fastest. The bike that was the fastest 24Wh/mi at 35.3mph avg was a Tour Easy with fairing and body sock. I'd love to have a small powerful light weight assist. Matt, I've been following the thread on your system and I would like to put one on my velomobile.

Bill B WAW velomobile running 48v AGM 18Ah with Crystalyte 406 20Ah controller
Distance: 12 laps (23.76 miles)
time: 45 min,
10 sec., Ave 31.1 mph,
Max Speed 34.2 mph,
energy used 335.7 Wh,
Usage per mile 14.12 Wh/

The bike that was the fastest was a Tour Easy with fairing and body sock.

Brent B GRR faired and full tail sock running 36vLi 20Ah with an EcoSpeed drive system
Distance: 15 laps (29.7 miles),
time: 50 min,
30 sec., Avg.: 35.3 mph,
Max Speed: 42 mph,
energy used: 700 Wh,
Usage per mile: 24 Wh

Image

Here are my stats for the three open track sessions and the race:

Sat morning................Sunday morning.....................Sunday afternoon..................Monday race
5 12V AGM 18Ah...........4 12V AGM 18Ah.....................4 12V AGM 18Ah...................4 12V AGM 18Ah
37.7miles...................19.5 miles............................21.3 miles..........................23.4miles
40.4 mph/max.............33.7 mph/max.......................32.9 mph/max....................34.2 mph/max
30.4 mph/avg..............27.3 mph/avg........................29.1 mph/avg.....................31.1 mph/avg

unknown....................288.7Wh--->14.80Wh/mile.........336.4Wh--->15.79Wh/mile......335.7Wh--->14.28Wh/mile
unknown....................20.73Ap................................20.92Ap...........................20.51Ap
unknown....................44.46Vm...............................45.42Vm...........................44.86Vm
unknown....................982.6Wp.............................1006.2Wp...........................969.2Wp
unknown......................6.02Ah...............................6.967Ah............................6.951Ah
unknown....................50.3V at end of run..................unknown............................50.5V at end of run
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Re: Extreme efficiency?

Post by paultrafalgar » Nov 03 2008 4:10am

Fascinating, Bill. How much does your battery weigh? I'd love to see you repeat that with some Lithium on board. I'd lay money on there being a big improvement in Wh/mile.
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Re: Extreme efficiency?

Post by Raphael » Nov 03 2008 5:01am

Hi,

I don't know if it helps, but this summer, my girfriend and me made a cross-country-tour through switzerland. As we have some pretty steep hills and also a good ready-to-go-weight (~40kg bike total), we surely used more energy than without those things.
We had an overall efficiency of around 5.5Wh/km which equals around 9Wh/mile. Yes we did pedal, but we are both not Lance Armstrong at all :). We made around 500km with 5 full charges (LiFePo4-batteries with 576Wh).
It's all been done on our SWB recumbents with a crystalite 407 motor in a 26" rear wheel. Average speed was around 32kmh / 20mph.

Not bad, right?
Raphael

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Re: Extreme efficiency?

Post by paultrafalgar » Nov 03 2008 5:23am

Too good to be true, Mr and Mrs Armstrong! Repeat without pedaling and report back! :wink: :lol:
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Re: Extreme efficiency?

Post by Raphael » Nov 03 2008 6:01am

aehemm... what'ya wanna tell me, Paul?

-If you wanna say I lie, discussion ends here for me. I'm not here to prove anything, but to share experiences
-If you think we didn't measure acurately, hmm, as I said, we have 2 bikes, both equally equipped, both with a CA
-If you think, the CA is off, I don't think so, because it would mean we get more than 576Wh out of our 48V/12Ah YESA-batteries
-If you wanna say that we did pedal a good amount, true, but the motor was on all the time where it made sense (read: NOT down the hill), but also our eyes were every 10 seconds on the CA

We really had an eye on energy-consumption, although the trip was for fun and not to set records. But I had planned the daily distances, and as we did those 500km in 3 days, there was more than 160km/day avg.

It's not interesting for me to see how much we would use without pedaling. For that, it's really the wrong equippement. We have a very low eta when climbing the hills slowly, and as I said, yes there are many hills around here (altough we did not cross the alps :))

I have a very exact calculation at home I once received from my uncle, where I can calculate the energy-requirements depending on drag etc. pp. We have made some measurements on the flat to compare and it's off no more than 1-3% depending on the speed. I'll let you know some numbers, I can calculate from 5-30mph and from 0-10% steepness.
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Re: Extreme efficiency?

Post by voicecoils » Nov 03 2008 6:51am

Raphael wrote:aehemm... what'ya wanna tell me, Paul?
I think Paul is just saying you pedaled hard! This is what makes ebike efficiency and power consumption hard to quantify: it's a hybrid system where one system is measured and the other system (human pedaling) is usually not measured.

Some day I hope to buy a Power Tap hub or SRM crankset. This will give me the best understanding of where the bike motion comes from: my legs or the motor, and what the ratio is.

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