Efficiency?

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DrkAngel   10 GW

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Efficiency?

Post by DrkAngel » Nov 19 2013 12:51am

Highlights & Index

Attack Them Hills!
Determining Peak Motor Output - Simple-Cheap Method
Electrical Input Watts vs Motor Output Watts
Motor Output Watts vs Speed - Aerodynamics
Motor "Watts" ... Input or Output?
Speed vs Range


Thought I'd graph a direct comparison of the electrical watts supplied into a motor and the actual motor output (watts) power.
Based on a 750w motor at full throttle ...
Watts in vs Watts out.jpg
Watts in vs Watts out.jpg (73.57 KiB) Viewed 9787 times
At 1mph energy efficiency is ~3% ... 97% wasted heat.
Flat line at low speed is the Amp limit of the controller.
A lower Amp controller reduces waste at low speed without affecting higher speed performance!

Best ... response?
Pedal assist getting started ... and up to more efficient speed?
Last edited by DrkAngel on Jul 24 2014 8:35am, edited 3 times in total.
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Re: Efficiency?

Post by DrkAngel » Nov 19 2013 1:22am

Bicycle type, (largely aerodynamics), determines the amount of power to acquire various speeds.
Image

Frontal area is not as much a factor as the shape of the frontal area!
Image
See - Aerodynamic Factors
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There, shallow draughts intoxicate the brain,
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Re: Efficiency?

Post by DrkAngel » Nov 19 2013 1:32am

Speed vs Range

Everyone likes more speed!
Well ... most everyone.

What most don't realize is the cost of more speed.
Pulled from the ebikes.ca simulator, I noted the various ranges supplied at different speeds.

Generic Mountain bike - motor only.
665w peak output motor w/48V 10ah battery = similar to a 24V 450w peak output eZip motor - pushed to 36V 675w peak output motor.

Anyway
10mph = 46 miles range
15mph = 30 miles range
20mph = 20 miles range
25mph = 13 miles range
30mph = 8 miles range

Wow! ... calculator - click click click ... Every 5mph increase in speed decreases range by 33%!

Most are shocked at the affect wind resistance plays.
Wind resistance is the major factor, but road load, tires, drive train etc. also contribute.

Makes me reconsider a lot!
Do I need 30mph capability? Nice to have it but ... don't need to use it! - OK! - Still a go.
Road Style bike with high pressure tires and crouched position? - Working on one!
Motor only, crouched behind an Aerodynamic fairing? Sounds almost essential - for sustained 30mph! - Battery pack mounted between bars and fork is a partial fairing. I'm sure I could easily enhance that!

Fortunately, I tend to cruise at 15mph, commute at 20mph with only very limited bursts nearing 30mph.

I'm even considering not upgrading (choke) my latest eZip Trailz LS.
(I use 3 eBikes + latest eZip, + building a road version and an eTrike ... also.)
OEM configuration is limited to 15mph in TAG (Twist And Go) mode and ~10mph in PAS (Pedal Assist System) mode.
Well, not upgrading, till after I run a range trial with my prototype 22.2V 40Ah pack.
I will add high pressure 1.75" tires for less rolling resistance and comfort seat and suspension post ... <15mph range trial might mean 5+ hours in the saddle!


A differing summation of watts required for a mountain bike to maintain various speeds.

*5mph = 22w
10mph = 68w
15mph = 163w
20mph = 333w
25mph = 601w
30mph = 993w
35mph = 1532w
40mph = 2247w
45mph = 3147w
50mph = 4280w
* from ebike.ca simulator

30mph requires almost precisely 300% the energy as 20mph.
Of course, it does not require 3x the energy per mile.
163w/15mph = 10.86wh/mile
333w/20mph = 16.66wh/mile
993w/30mph = 33.1wh/mile
Still 30mph require 2x the energy per mile, or ...
Same ~36V 10Ah battery ...
15mph = 30+ mile range or - 92.08 miles per kWh = 6 hour cruise time
20mph = 20 mile range or - 60.02 miles per kWh = 3 hour cruise time
30mph = 10 mile range or - 30.21 miles per kWh = 1 hour cruise time
Last edited by DrkAngel on Jun 02 2016 9:15am, edited 1 time in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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DrkAngel   10 GW

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Re: Efficiency?

Post by DrkAngel » Nov 19 2013 2:06am

DrkAngel wrote:Thought I'd graph a direct comparison of the electrical watts supplied into a motor and the actual motor output (watts) power.
Based on a 750w motor at full throttle ...
Image

At 1mph energy efficiency is ~3% ... 97% wasted heat.
Yes efficiency at low speeds is horrific!!!
Worse?
Worse!
SLA batteries at a 1C discharge rate are only ~50% efficient.
With the same setup in graph, SLA battery would waste an additional 2750w at 1 mph.
Effectively wasting 5400w to produce 100w of usable energy.
(Much worse actually, it would require much higher than a 1C discharge rate from the SLA, producing much worse efficiency. )
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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DrkAngel   10 GW

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Re: Efficiency?

Post by DrkAngel » Nov 19 2013 5:26pm

DrkAngel wrote: Yes efficiency at low speeds is horrific!!!
The good news?
Inefficiency can be regulated through the use of throttle restraint!
At most any speed maximum efficiency is attainable.
Of course this will limit acceleration ...

But, since the worst region is from a standstill till mid-speed, the application of pedal assist combined with moderated throttle can deliver satisfactory acceleration.

Some eBikes incorporate a PAS system and a delay that seeks to "work around" the worst area of energy waste.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Re: Efficiency?

Post by Hillhater » Nov 19 2013 7:37pm

DrkAngel wrote:Thought I'd graph a direct comparison of the electrical watts supplied into a motor and the actual motor output (watts) power.
Based on a 750w motor at full throttle ...
Watts in vs Watts out.jpg
How come this graph suggests the motor uses less power at 30+ mph , than at 15 mph ?
..or is this just unloaded rpm rather than actual road speed ?
This forum owes its existence to Justin of ebikes.ca

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DrkAngel   10 GW

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Re: Efficiency?

Post by DrkAngel » Nov 19 2013 8:11pm

Hillhater wrote: How come this graph suggests the motor uses less power at 30+ mph , than at 15 mph ?
..or is this just unloaded rpm rather than actual road speed ?
"Full throttle"
Actually, somewhere near 25mph(?) air and rolling resistance overwhelms motor output, eBike is accelerating till that point.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Re: Efficiency?

Post by TheBeastie » Nov 19 2013 10:37pm

DrkAngel wrote:Speed vs Range

Everyone likes more speed!
Well ... most everyone.

What most don't realize is the cost of more speed.
Pulled from the ebikes.ca simulator, I noted the various ranges supplied at different speeds.

Generic Mountain bike - motor only.
665w peak output motor w/48V 10ah battery = similar to a 24V 450w peak output eZip motor - pushed to 36V 675w peak output motor.

Anyway
10mph = 46 miles range
15mph = 30 miles range
20mph = 20 miles range
25mph = 13 miles range
30mph = 8 miles range

Wow! ... calculator - click click click ... Every 5mph increase in speed decreases range by 33%!

Most are shocked at the affect wind resistance plays.
Wind resistance is the major factor, but road load, tires, drive train etc.
Nice.
Yeah this type of information just/isn't posted enough. In fact I feel like sticking some of your information in my signature.
So many people tend to be under the belief that if they just go fast enough then they can some how increase there range, when it just couldn't be any more the opposite.

Its like speed can somehow magically outrun any logic. Makes me think of the Delorean at 88mph...

It makes sense that the first mass market electric wheel was the powered wheel chair that must of started so many decades ago, these were viable because they went so slow.

Its the same deal with cars as well, the Bugatti Veyron at 254 Mph eats more then 1 gallon of fuel per 3 miles or for metric folks 78 Liters/100 km. https://en.wikipedia.org/wiki/Bugatti_Veyron ctrl+f "3 miles per" In fact the car wouldn't need to go much faster to hit the perfect 100 Liters per 100km, or 1 Liter per kilometer, as the inefficiency just increases with speed..
Is anyone out there now thinking well maybe if it could go even faster like 300mph it could some how reverse that? Noooo!

*Add*
I decided to add this video here as I thought it was a great visual video to see how much air slows you down, what this video in full it has to be seen to be believed.. got it from here https://www.facebook.com/dafne.fixed/vi ... 135301364/
Last edited by TheBeastie on Aug 25 2016 9:43am, edited 11 times in total.
Speed Kills Range, 10mph = 46 miles range, 20mph = 20 miles, 30mph = 8 miles range https://goo.gl/1JNL53
Over Charging Kills ur battery bit.ly/1hzWKl4
Consider PAS as your only throttle https://goo.gl/Kg1F8F
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https://goo.gl/gfa215
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Re: Efficiency?

Post by dogman dan » Nov 20 2013 7:48am

Maybe you should put this information into the wiki?

So obvious to us now, but when we started we had no idea.

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Re: Efficiency?

Post by DrkAngel » Nov 20 2013 11:42am

dogman wrote:Maybe you should put this information into the wiki?

So obvious to us now, but when we started we had no idea.
Not so obvious ... ?

Sadly ... It seem a goodly percentage of members still rate their systems (motor-controller-battery) by the watt input rather than the motor output watts.
Last edited by DrkAngel on Nov 20 2013 1:49pm, edited 1 time in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Re: Efficiency?

Post by DrkAngel » Nov 20 2013 1:49pm

DrkAngel wrote:
dogman wrote:Maybe you should put this information into the wiki?

So obvious to us now, but when we started we had no idea.
Not so obvious ... ?

Sadly ... It seem a goodly percentage of members still rate their systems (motor-controller-battery) by the watt input rather than the motor output watts.
The same 1500w input could output anywhere between 50w- and 1300w+ usable ...

Well ... some claim that their "system" can run 1500w continuous input without overheating, and that is why they claim 1500w.

What actually happens is that, at a maintainable speed, watt input is 1500w, with no overheat.
So they are likely cruising near peak efficiency ... possibly 80% efficient.
That would be 1200w usable and 300w damaging heat.
The same 1500w input at slower speed, up a hill?, might output 500w usable power and 1000w damaging heat.
To keep the motor from overheating they would have to reduce heat to ~300w or - by reducing watt input to 1/3rd?

So their "1500w" is now a 500w ... by their same reasoning ... ?

The only way to accurately rate their motor system, using their reasoning, would be to rate the motor by its continuous heat dissipation potential ... 300w?
Last edited by DrkAngel on Nov 20 2013 11:56pm, edited 1 time in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

New & Improved - Acronym Definitions

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Re: Efficiency?

Post by gogo » Nov 20 2013 3:16pm

DrkAngel wrote:
DrkAngel wrote:
dogman wrote:Maybe you should put this information into the wiki?

So obvious to us now, but when we started we had no idea.
Not so obvious ... ?

Sadly ... It seem a goodly percentage of members still rate their systems (motor-controller-battery) by the watt input rather than the motor output watts.
The same 1500w input could output anywhere between 50w- and 1300w+ usable ...

Well ... some claim that their "system" can run 1500w continuous input without overheating, and that is why they claim 1500w.

What actually happens is that, at a maintainable speed, watt input is 1500w, with no overheat.
So they are likely cruising near peak efficiency ... possibly 80% efficient.
That would be 1200w usable and 300w damaging heat.
The same 1500w input at slower speed, up a hill?, might output 500w usable power and 1000w damaging heat.
To keep the motor from overheating they would have to reduce heat to ~300w or by reducing watt input to 1/3rd?

So their "1500w" is now a 500w ... by their same reasoning ... ?

The only way to accurately rate their motor system, using their reasoning, would be to rate the motor by its continuous heat dissipation potential ... 300w?
A good illustration of this would be an example of a motor/controller/battery that could actually deliver 750 watts continuosly through the contact patch of the tire against a 30 MPH headwind, or up a specified incline (@ a specified mass) without overheating.
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Re: Efficiency?

Post by LockH » Nov 20 2013 3:34pm

Actually, I am reliably informed that in urban environments, the faster you go, the faster you might kill yourself (or other peds, cyclists, small furry animals, snakes, etc). So this thread/info is *very* useful! Pls "sticky" this thread here, somebuddy, please?
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Re: Efficiency?

Post by Hillhater » Nov 20 2013 5:16pm

DrkAngel wrote:
Hillhater wrote: How come this graph suggests the motor uses less power at 30+ mph , than at 15 mph ?
..or is this just unloaded rpm rather than actual road speed ?
"Full throttle"
Actually, somewhere near 25mph(?) air and rolling resistance overwhelms motor output, eBike is accelerating till that point.
?? no, your first graph indicates approx 750W at 15 mph, 300W at 30 mph, and tending to zero at 35 mph ?
So i was trying to figure why your first graph doesnt correlate to this info ??...
DrkAngel wrote:.. watts required for a mountain bike to maintain various speeds.
15mph = 163w
20mph = 333w
25mph = 601w
30mph = 993w
35mph = 1532w
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Re: Efficiency?

Post by DrkAngel » Nov 20 2013 5:45pm

Hillhater wrote:
DrkAngel wrote:
Hillhater wrote: How come this graph suggests the motor uses less power at 30+ mph , than at 15 mph ?
..or is this just unloaded rpm rather than actual road speed ?
"Full throttle"
Actually, somewhere near 25mph(?) air and rolling resistance overwhelms motor output, eBike is accelerating till that point.
?? no, your first graph indicates approx 750W at 15 mph, 300W at 30 mph, and tending to zero at 35 mph ?
So i was trying to figure why your first graph doesnt correlate to this info ??...
DrkAngel wrote:.. watts required for a mountain bike to maintain various speeds.
15mph = 163w
20mph = 333w
25mph = 601w
30mph = 993w
35mph = 1532w
"Graph" has nothing to do with "info".
Graph is maximum motor output.
Info is minimum watts required to attain specified speeds.

1st graph is - full throttle maximum output from a "750w motor" - 35mph is not attainable, it is just motor output (maximum 25mph, ~600w, might be possible ).
"Info" = watts required to sustain specified speed.
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Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Re: Efficiency?

Post by Hillhater » Nov 20 2013 6:59pm

OK so enlighten me again.
Graph... at 30mph the motor is producing 300Watts ... yes ?
so what exactly is this motor driving at 30 mph ? ..obviously not a mountain bike, or even a recumbent !
Normally data like this would be obtained from logging power vs road speed, but if that were the case for this motor it would not even get to 30mph ?
How was this data logged ?
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Re: Efficiency?

Post by DrkAngel » Nov 20 2013 7:55pm

Hillhater wrote:OK so enlighten me again.
Graph... at 30mph the motor is producing 300Watts ... yes ?
so what exactly is this motor driving at 30 mph ? ..obviously not a mountain bike, or even a recumbent !
Normally data like this would be obtained from logging power vs road speed, but if that were the case for this motor it would not even get to 30mph ?
How was this data logged ?
At 30 mph the motor is providing a percentage of the power required for that speed.
I didn't think a load line was necessary.

All stats were gleaned from http://ebikes.ca/simulator/
ebike_ca_simulator.jpg
ebike_ca_simulator.jpg (106.46 KiB) Viewed 9568 times
Watts in vs Watts outSq.jpg
Watts in vs Watts outSq.jpg (55.01 KiB) Viewed 9568 times
Last edited by DrkAngel on Apr 29 2016 6:22am, edited 1 time in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Re: Efficiency?

Post by TheBeastie » Nov 20 2013 10:45pm

dogman wrote:Maybe you should put this information into the wiki?

So obvious to us now, but when we started we had no idea.
Well I have added it to my signature, my annoying posts are riddled everywhere.
If you don't approve DrkAngel please just request me to be perm banned and my ip firewalled from the server. :x
Speed Kills Range, 10mph = 46 miles range, 20mph = 20 miles, 30mph = 8 miles range https://goo.gl/1JNL53
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Re: Efficiency?

Post by dogman dan » Nov 21 2013 9:31am

So how do you easily measure this output wattage at the point where the rubber meets the road? How else can we rate our system?

I learned to watch watts leaving the battery, and mentally compare that to what the temp sensor in the motor was showing, to get a rough idea when I was riding efficient and when I was not. The temp gage shows very quickly when you have a 500w heater in your hub. But I'm still guessing at the real efficiency.

You can also compare watts in to mph, and get an idea how much extra work your motor is doing at a given moment, but it does not tell you when you have slowed to an inefficient rpm.

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Determining Peak Motor Output - Simple-Cheap Method

Post by DrkAngel » Nov 21 2013 10:32am

dogman wrote:So how do you easily measure this output wattage at the point where the rubber meets the road? How else can we rate our system?

I learned to watch watts leaving the battery, and mentally compare that to what the temp sensor in the motor was showing, to get a rough idea when I was riding efficient and when I was not. The temp gage shows very quickly when you have a 500w heater in your hub. But I'm still guessing at the real efficiency.

You can also compare watts in to mph, and get an idea how much extra work your motor is doing at a given moment, but it does not tell you when you have slowed to an inefficient rpm.
Observing the ebike.ca\simulator, I notice a consistent ~50% relation of input watts to watts output occurring at ~40% of no load motor speed.
Using this, it is possible to determine peak motor output.

Image
"Inefficient rpm" is critical, but as important are the input amps at low rpm.
With sufficient throttle restraint, most any rpm is capable of fair to good efficiency ... if sufficient motor output to maintain speed.
Attachments
50% input at 40% no-load speed.jpg
50% input at 40% no-load speed.jpg (106.73 KiB) Viewed 1803 times
Last edited by DrkAngel on Apr 26 2016 7:40am, edited 7 times in total.
A little learning is a dangerous thing;
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There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Re: Efficiency?

Post by speedmd » Nov 21 2013 10:50am

Something like this for a mid drive may work pretty well for lower powered setups.
Image

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Determining Peak Motor Output - Simple-Cheap Method

Post by DrkAngel » Nov 21 2013 11:50am

DrkAngel wrote:
Observing the ebike.ca\simulator, I notice a consistent ~50% relation of input watts to watts output occurring at ~40% of no load motor speed.
Using this, it is possible to determine peak motor output.
(Based on controller capable of maximum amp supplied at 40% of no load speed)
1. Determine no-load maximum motor speed - digital speedometer on motor wheel, blocked up (EG - 36mph)
2. Multiply no-load speed by 40% (EG - 36mph x .40 = 14.4mph)
3. Cruise near 14.4mph, Apply full throttle and note watt usage as speed hits-passes 14.4mph (1498w x .50 = 749w motor output)
(Precise 50% of input occurs at 38.6% of no-load speed- 13.9mph (this EG) ... but 40% is a fairly close, easy to figure number )

40% of no-load speed intersects 50% efficiency near the center of peak watt output nicely!
Image

Surprisingly, this seems fairly consistent among all the simulations I have tried and looks to be a reasonably reliable measure.
"Reasonably" accurate!
Not precise but accurate within a few percentage.
(The exception is if the controller is of inadequate amps to allow maximum peak watt output.)

Update - I just sampled various-more motor types and found a variance of ~ 40% to almost 50% (Clyte) of no load speed as the peak watt output and 50% efficient point.
These might be non-permanent magnet motors?
There is such a clear shift of 50% efficiency that a differing motor type is clearly indicated!
The 50% efficiency point remains firmly within the peak watt output region!
Last edited by DrkAngel on Mar 24 2015 9:17am, edited 4 times in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

New & Improved - Acronym Definitions

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teklektik   10 GW

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Re: Determining Peak Motor Output - Simple-Cheap Method

Post by teklektik » Nov 21 2013 4:30pm

DrkAngel wrote:Observing the ebike.ca\simulator, I notice a consistent ~50% relation of input watts to watts output occurring at ~40% of no load motor speed.
...
Update - I just sampled various-more motor types and found a variance of ~ 40% to almost 50% of no load speed as the peak watt output and 50% efficient point.
The 50% efficiency point remains firmly within the peak watt output!
Justin calls out this characteristic in the "How To" section immediately under the simulator on the web page:
Justin wrote:Red Plot: The red line shows the power output of the hub motor. The power output is zero at 0 rpm, rises up to a maximum, and then falls back down to zero once the wheel is spinning at its normal unloaded speed.

If the motor current is not limited by the controller in any way, then the peak power happens at between 40-50% of the motor's unloaded rpm.

Otherwise, the maximum power usually coincides with the point when the controller hits the current limit.
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dogman dan   100 GW

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Re: Efficiency?

Post by dogman dan » Nov 21 2013 4:33pm

Efficient rpm at any speed with throttle control. Yes, on the flat paved.

But once on the hill, things get weird with hubmotors. You just gotta keep out of that inefficient rpm for your winding. A thermometer inside tells you fast when you are inefficient. You should be seeing a very slow temp rise to eventual equilibruim, but if it's fast, you know you are blowing watts into heat fast.

On the hill, much depends on your winding, the grade, and how much you can pedal your guts out to keep the rpm right for the winding and wheel size you are running. On dirt, you better blast through the deep sand. You will melt a hubmotor even faster than on hills bogging in the sugar sand. I can ride 5 mph using 200w in just an inch of loose dirt, with wide tires too!!! On paved, you'd be going 10 mph faster on that. Even at 200w, the hub just hates 5mph. But on paved, 5mph just means you are using 50w. Hard to overheat at 50w. A pedal stroke then triples your power.

Half throttle and pedal usually does work fine on paved hills, to about 10% grades on typical 26" hubmotor kits. The idea is to try to maintain 15 mph speed up that hill. It's all about matching the heating rate with your radiation rate, so the hub doesn't just keep getting hotter an hotter too fast to last the length of the hill. Big trouble if the hill is 5-10 miles long like we have here. Less throttle means less wattage from the waste part of the power. Then pedal back up to a more efficient rpm, and you are good to go. You might get hot, but not hot enough to melt down. Its how I climbed big mountains with the wrong, too fast, winding on those aotema motors I had.

But you don't see it discussed much here. Here, it's all the throw another 1000w at it club. :mrgreen:

I've learned to choose the right winding for the task, rather than have to ride half throttle on the hills. Pick the efficient winding if you climb a lot. Then rip up them at full speed, perhaps still only 12 mph, but with a cool motor.

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DrkAngel   10 GW

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Attack Them Hills!

Post by DrkAngel » Nov 24 2013 9:19am

For climbing hills,

It is important to keep speed-rpm above 40-50% of no-load motor speed! (Percentage dependent on motor design.)
This is the point of maximum possible watt output and 50%+ efficiency.
Above this point efficiency increases - Below this point output efficiency decreases and output diminishes - quickly!

Attack the Hill!

Get a good run at it, faster is better!
Pedal assist at a moderate strength, so as to maintain higher speed-efficiency for as long as possible.
As, speed diminishes towards maximum watt output, increase your pedal assist effort.
The object is to keep motor rpm-speed as high as possible,
more importantly,
to maintain above the maximum watt output point!
(Effort might need to be rationed, dependent of length of hill.)

From top "attack speed", efficiency decreases with speed loss, but motor output increases.
It is important to maintain above the 40-50% of no load speed...
because ...
Below this maximum motor output, efficiency decreases, but motor output decreases as well!
A double whammy!

If maintainable speed drops noticeably below this efficiency point,
due to heat production, it becomes important to reduce throttle-watts input.
Sadly, while doing this decreases heat production it also decreases motor output, putting you in a downward spiral of speed loss and heat production ...

So ... Attack them hills!
Last edited by DrkAngel on Jan 12 2017 10:33am, edited 3 times in total.
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