Ebike efficiency ?

P

PetriK

10 mW
Joined
Nov 22, 2010
Messages
27
My watts up shows 850w in to the controller, just trying to figure out how much power to the wheel to estimate comparable kilowatts/horsepower number ?


Infenion Controller efficiency ?
Bafang hub motor efficiency ?
Bagang internal gear loss ?
Wiring loss from controller to motor ?

Maybe e.g. 90x90x85x97x850w ?
 
Stick it on a dyno :)

ebikes.ca has a fairly good efficiency calculator, you can check that out and get an idea..
Of course, the efficiency isn't in percent, so hmm..
 
Our dyno has a 450kg drum and eddy currrent brake. In practise the load from dyno is too big to have more than around 0.5hp tolerance, which may be as much as this motor gives out.

Thanks for the ebikes.ca hint.
 
Looked at the ebikes.ca and that does not seem to include planetary gear loss into the equation. Additionally the choises are far from what I have in the bike, as product names.

Motor efficiency seems to be minimum 80 up to 95 depending on sources
Planetary gear efficiency seems to be around 95 to 97
Controller efficiency i dont know, maybe 90, but will surely increase after changing fets to lower resistant ones
Wiring loss have not measured, but surely some percentage.

With 850w in to the controller, looks like we may be talking about 500-600w out at wheel ?

As the battery pack can not really take too much more load wihtout sacrificing long term capasity therefore the next step should be to minimize losses.

Would appreciate some real test data and views to theorethical losses based on different specs...
 
You do lose some power in the planetary gears, but you make up for it with a much wider efficiency curve on a geared motor ( at least according to ebikes.ca! )

I'd guesstimate that there's an overall 75% loss from the battery to the wheel.
Hey, it's better than internal combustion, which is like ~20% efficient :p
 
neptronix said:
I'd guesstimate that there's an overall 75% loss from the battery to the wheel.
Hey, it's better than internal combustion, which is like ~20% efficient :p
Click to expand...

One watt hour will lift one kg 360 metre (approx) or 360 kg one metre. Therefore, if you were using the motor "only to help on hills," a perfectly efficient ebike weighing 120 kg in all could never flatten more than three metres of climbing per watt hour used. I don't know about the rest of you, but my best real-world usage is 2-3 times that.
 
PetriK said:
Motor efficiency seems to be minimum 80 up to 95 depending on sources
Click to expand...
That would be the peak efficiency, though. Efficiency varies with torque load. Torque is proportional to current. Direct losses go up as the square of the phase current.... At half of the stall torque, efficiency is close to 50%.
 
neptronix said:
I'd guesstimate that there's an overall 75% loss from the battery to the wheel.
Hey, it's better than internal combustion, which is like ~20% efficient :p
Click to expand...

I hope the author meant 75% efficiency not loss...

So what are the biggest loss generaring components that can be affected ?

My battery switch gets warm, so must be one potential area as heat means loss. Also fets in controller are still original. But thats it as much as i can figure out of what to improve to make the configuration more energy efficient.
 
PetriK said:
neptronix said:
I'd guesstimate that there's an overall 75% loss from the battery to the wheel.
Hey, it's better than internal combustion, which is like ~20% efficient :p
Click to expand...

I hope the author meant 75% efficiency not loss...

So what are the biggest loss generaring components that can be affected ?

My battery switch gets warm, so must be one potential area as heat means loss. Also fets in controller are still original. But thats it as much as i can figure out of what to improve to make the configuration more energy efficient.
Click to expand...

Lol, that's what i meant, 75% efficiency, sorry folks..

The best thing you can do for efficiency, is..
Run the lowest amount of power possible and pedal like crazy ;)
Go slow to avoid aerodynamic losses ( 20mph is where it starts getting gnarly )
Make sure nothing is heating up due to excessive resistance ( connectors, wires, even batteries if you are pushing them beyond their C rating )

etc..
 
go check out analyticcycling.com

Input your weight and rolling resistence figures on a steady hill grade that you know. That should show you what power is going to the wheel for a given speed.

I've noticed it's around 75-80% efficiency.

Oh I can't wait till battery technology allows a small lightweight battery that is turnkey, safe and inexpensive....
 
Thx, picked up tire pressure and inert mass and frontal area. On my other hobby i try to save grams for better accelearation and speed.

Tires are already changed to less rolling resistance ones ( according to sales pitch ) and pumped to overpressure.

Sounds like the most efficient method would be to loose body mass, thats inert and has biggest effect to frontal area ;)

The issue i have is really battery C ratio. Now 850w peak out of 36v 10Ah pack is to the limit, even though the average consumption is only around 3Ah/hour.
 
PetriK said:
The issue i have is really battery C ratio. Now 850w peak out of 36v 10Ah pack is to the limit, even though the average consumption is only around 3Ah/hour.
Click to expand...

3ah/hour? You must mean a different figure..

At that rate you're saying you can get at least a 3 hour rub time from your 36v 10ah batt..
That seems a little off.. Let's say your average speed is 15mph, then that means 45miles out of a 10ah battey... Doesn't make sense
 
Sure it does. Anybody can pedal along with the motor pretty much off. That's about what's happening anytime you see less than 20 wh/mile.

You can pedal on the flat using about 50 watts for miles and miles and miles if you want to. But most of us would rather use about 200 watts or more and go faster/ easier. At 200 watts you'd still get a few hours out of a 10 ah battery.
 
360wh divided by 45 miles is 8th/mile..
That figure would require pedaling nonstop and not using the motor pretty ever...
In my opinion, Not really worth it to have the added weight of the motor and battery at that point.
 
On all the different setups i've built and tried ( .. like.. .ALOT of them ) .. i can get aprox 10 wh/km if a cruise slowly ( 10 to 15 mph / 20 km/h or so.. ) the faster you go the more you waste.. this can be done with an X5 powered chopper that weighs almost 100 lbs to a 36v eZee kit on an aluminum mtb... . no pedaling.. just pulse and glide with carefull throttle use.

Biggest factors are tires, pavement material ( the rough stuff vs smooth, and temperature also factor in , wet road is more efficient for some reason i canot explain )
 
IMO,

The two BIGGEST factors are wind against me and how many stops/starts I have.
(Forget about hills, I live in Florida)

There's a huge difference between being able to constantly cruise at 10-15mph with no wind against you / no stops and wind against you and stopping every 1/4 mile.

I have seen difference of 30% or more...

Worst case scenario for me is 20mph, with wind against me, stopping every 1/4 mile and only get 70 miles.
Best case scenario was no wind against me, 20mph and barely any stopping and get 116 miles.

Dual 36v 250w motors and dual 36v 20ah LiFePo4 batts.
1440 KwH.
70 miles is ~21 wh/mile
116 miles is ~12.5 wh/mile
 
Last trip according to gps and watts up 2.1ah, ~40min, 14.5km average speed 21km/h, top speed 37km/h. Peak 24Ap.

Averag hr most of the time 110-130, i.e. 60% on that range so not so heavy.

Its a 10ah battery, so lools like i could get some 50-60 km out of it down to 20% level.

Bike is fairly light 2008 kona four deluxe full suspension with racingn ralph tyres pumped to 3.5bars. Pedelec config, only 3 position duty cycle switch and pas sensor.

So is my wattsup broken already then ???
 
Nope.. Wattsup is working perfectly...

NOW I see why such low wh/mile..
8.5mph avg, 12.6mph max AND pedal assist...
That makes perfect sense, NOW!! :)
 
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