Geared vs direct drive effeciency

bowlofsalad

bowlofsalad

100 kW
Joined
Feb 1, 2013
Messages
1,540
Location
Midwest, USA
Hello,

Sorry if this is posted in the wrong place.

I've been shopping around for various kits. http://www.e-bikekit.com/ebike-kits/electric-bike-motor I came across this page claiming that the geared hub is 15%-25% more efficient than direct drive. I understand that this could be marketing, so I thought I'd ask here. Is geared more efficient? 15-25% seems pretty crazy. Some people say regenerative braking is a waste of time, some folks say they gain 5-10%, some less, some a bit more with regenerative braking. While I don't know about all that, geared sounds like it steps well ahead of regenerative braking.

The only real downside (in my opinion) is the noise, but it seems like some decent lubrication would fix that nicely, I don't know for sure though. I did come across a thread saying they used automotive transmission fluid in their geared hub and it cut the noise dramatically. Some might say a lower top speed is a serious thing to avoid, but I really don't wish to go much if any beyond 20 mph, besides, the difference in speed isn't much. I prefer the idea of range when it comes to an ebike, and 20mph is plenty fast.
 
The questions you ask have been answered many many times before, just search the forum.

As for noise both DD and geared both make noise, the noise is slightly different but neither is exactly loud or obvious IMO.

You can use the simulator to see the differences between geared and DD hubs:

http://www.ebikes.ca/simulator/

Kudos
 
http://www.endless-sphere.com/forums/search.php?keywords=Geared+vs+direct+drive+efficiency&terms=all&author=&sc=1&sf=titleonly&sk=t&sd=d&sr=topics&st=0&ch=300&t=0&submit=Search
http://www.endless-sphere.com/forums/search.php?keywords=Gear*+efficien*&terms=all&author=&sc=1&sf=titleonly&sk=t&sd=d&sr=topics&st=0&ch=300&t=0&submit=Search
probably other searches with variations on your thread title will find more.
 
The difference can be that much, or not if the top speeds of the two motor types are closer to each other. A gearmotor capable of 20 mph will use less power than another motor run at 23 mph. In addition, the type of ride can matter, with the gearmotor tending to have an advantage if there are lots of stop signs. But a slower dd motor that the one typically sold can be just as good on a route with many stops. But unable to go so fast.

If you take both kinds, and run them both at say 18 mph for 5 or more miles with no stops or hills, you'll see very similar wh/mi out of both of them.
 
Efficiency has very little to do with choice between the two designs. As Dogman pointed out, same route, same speed, same conditions, will be hard to notice much difference in power consumption.

As far as the decision of which type to choose IMO 'has more to do with: weight, torque (hills/trailers), regen, hot rodding and potential longevity. 100% bet is to simply build one of each and use BIS (butt in seat) to determine your preference.
 
I agree with dogman and Ykick, it depends on your preferences as to which motor is better suited for your tasks. If you have hills and such to ride on all the time then the geared motor would be the better choice over the DD motor.
 
I think the biggest benefit the geared offers over the direct drive is a significant increase in torque and responsiveness watt for watt up to a certain point. For example my old Crystalyte 407 with a 20 amp controller at 48 volts felt pretty under powered from stop till it reached 15 to 20kph, when compared with an older bmc running at 36 volts and I believe same 20 amp controller. Even though the geared was using less power than the direct drive there was a big difference in responsiveness at lower speeds, specially from stops.
 
electr0n said:
I think the biggest benefit the geared offers over the direct drive is a significant increase in torque and responsiveness watt for watt up to a certain point. For example my old Crystalyte 407 with a 20 amp controller at 48 volts felt pretty under powered from stop till it reached 15 to 20kph, when compared with an older bmc running at 36 volts and I believe same 20 amp controller. Even though the geared was using less power than the direct drive there was a big difference in responsiveness at lower speeds, specially from stops.
Click to expand...

I totally concur, my currie motor had torque unlike the new motor and taking off from a dead stop the currie motor blows the DD motor out of the water 8)
 
RLD70 said:
I totally concur, my currie motor had torque unlike the new motor and taking off from a dead stop the currie motor blows the DD motor out of the water 8)
Click to expand...

Yes, well try putting 2000w into your currie motor and 2000w into your DD motor and see what happens. :lol:


Geared motors typically have pretty broad efficiency curves, and the larger ones can be more efficient while climbing hills, but on average they are not more efficient, either on par with similar sized DD motors or a few percent less efficient on the flats.

ebikekit's geared motor is a good motor, but it's capable of far less power than what their DD is capable of, and likely has 5%-10% lower efficiency as well. Now if you were to compare that DD to a MAC or BMC geared motor, it'd be a different situation. The MAC/BMC motor's efficiency would be within a few percentage points of the DD, and the torque would be a bit better.

ebikes.ca's motor simulator can help you understand what i'm talking about better.

http://ebikes.ca/simulator/
 
I think the efficiency would really depend on the type of riding you do as well. Typical city riding with a lot of stop and go, slowing down for pedestrians if riding on sidewalks or hilly terrain I would expect the geared motor to be more efficient than the direct drive maybe significantly if hitting the throttle hard and you like pulling hard from stops. The direct drive efficiency should only be more efficient when it's running at near it's top speed at whatever voltage it's at which at least for me is most often not the case.
 
neptronix said:
RLD70 said:
I totally concur, my currie motor had torque unlike the new motor and taking off from a dead stop the currie motor blows the DD motor out of the water 8)
Click to expand...

Yes, well try putting 2000w into your currie motor and 2000w into your DD motor and see what happens. :lol:


Geared motors typically have pretty broad efficiency curves, and the larger ones can be more efficient while climbing hills, but on average they are not more efficient, either on par with similar sized DD motors or a few percent less efficient on the flats.

ebikekit's geared motor is a good motor, but it's capable of far less power than what their DD is capable of, and likely has 5%-10% lower efficiency as well. Now if you were to compare that DD to a MAC or BMC geared motor, it'd be a different situation. The MAC/BMC motor's efficiency would be within a few percentage points of the DD, and the torque would be a bit better.

ebikes.ca's motor simulator can help you understand what i'm talking about better.

http://ebikes.ca/simulator/
Click to expand...

Well their new 500w rear motor is yet to be announced and Im willing to bet that its more on par with their dd motor and ebikes.ca, been there done that. Thanks for the thought though 8)
 
Hah, I figured others have asked this question, I always do lots of searching, but more often than not, I am using the wrong terms for searches.

There seems to be plenty of different perspectives and opinions on this matter. At least, many things to consider between the two.

It's hard to know which is better, they seem fairly situational. My plan on riding is for efficiency. So I aim to pedal from each stop to around 10mph and then stop pedaling and cruise to 20mph with the electric motor. I theorize this will yield excellent range results. I can't really tell for sure which would give better results at cruising around 20mph, I imagine geared could be a better hill climbing option, but it seems hard to know. After doing some more reading, it seems like maybe direct drive might be the way to go. At least that way I wouldn't have to mess around with the nylon gears.
 
bowlofsalad said:
My plan on riding is for efficiency. So I aim to pedal from each stop to around 10mph and then stop pedaling and cruise to 20mph with the electric motor. I theorize this will yield excellent range results.
Click to expand...

Good luck with that mentality. After awhile the lazy thumb bug will affect you and you'd just throttle through everything. The only time I feel "miserly" with my energy consumption is when I know I've used up 2/3rds of my capacity and have to guestimate whether I would make it to a charge (i.e. home, destination, outlet, etc.). Other than that, I'm really throttling at over 60% of my "stop & goes". In reality, most of the routine rides that we do fall well above our battery's LVC, but there are times when doing a bit of exploring/adventuring really treads into new territory with our battery's ability.
 
I have always found gear motors to be much lighter and use less current than DD for my routes that have some hills on them. The noise is significantly greater which makes me stay with DD. Good enough starting torque and quiet. But perhaps the newer geared motors from Bafang, BMC etc are quieter than my older Bafangs. I have always like the roller geared motors as they are light and quiet, and ebikes.ca is testing some now. They have only fronts, however and I prefer rear mount.
otherDoc
 
Set a steady speed with the throttle, then pedal enough to go 1-2 mph faster is my recipe for the max efficiency for a given speed. The idea is to actually put about 100w in, which means your battery is 100wh bigger if the ride lasts an hour. Pedal the first 10 feet can save a lot of power, that's a true fact.

But to really stretch range, it's all about how slow can you stand to ride. Same battery can take me 20 miles or 40. At some point, when really slow, your 100w effort is 50% of the power.

In practice, day in day out, a 350 w motor can be much more efficeint, in a way, because you can't use more. While a 1000w motor is less efficient, in a way, because you can use more when the little brain in your throttle hand is doing the thinking.

But I'd rather have a powerfull motor turned down with a three speed switch when the wind is 40 mph in my face. A real head wind can nearly stop a little motor. If you get wind, turn up the switch to high power rather than suffer.

On the other hand, if keeping the whole bike light is your aim, go for the little gearmotor.
 
Im still getting a geared motor provided nothing major happens between now and then and the question is will it be the 600w BMC or the new 500w E-BikeKit motor. As long as the motor can handle upto 2000w and not break a sweat during hauling and is reasonably priced will be the one I get. Dont get me wrong I like the DD motor thats on the bike right now but something tells me that the geared motor is the better overall choice for my needs even though I have the feeling that the DD motor will handle the hauling too just not a s good as the geared motor. I miss the power that the torque motor gives me but like I said, the DD motor is an awesome thing in and of itself.
 
None of the motors you mentioned can take 2000W and not break a sweat. They will all turn a lot of that energy into heat. Short 2000W peaks? no problem. 2000W continuous? you'll melt a MAC or 9C at that power level.

The smallest motor you want to go with is a magic pie or Crystalyte HS/HT for that kind of power, if it is continuous.
 
bowlofsalad said:
My plan on riding is for efficiency. So I aim to pedal from each stop to around 10mph and then stop pedaling and cruise to 20mph with the electric motor. I theorize this will yield excellent range results.
Click to expand...
If you really want to be efficient, then not using any human power will actually be more so, based on past discussions of the total energy used up to create the calories you'll burn, vs the total energy used up to create the Wh the motor will use.


But if you're simply looking for better range out of the batteries, ignoring anything of human efficiency, then yes, you'll certainly get better range by that method, as the most motor power is "wasted" at startup from a stop, and at least the first part of accleration to a speed.


In my limited experience (Fusin geared vs 9C DD), once you're past a few MPH then accleration on either one seems just about as efficient. At start-from-stop up to that point, the geared motors I've used seem to be more efficent vs the 9C DD, but that is specific to those motors. If a DD motor was wound to be more efficient at the lower speeds, it would probably beat the geared ones that aren't.


Unfortunatley there is no "answer" to the question, other than "it depends". ;)
 
Use cash you'd take to vegas and blow, if you plan on 2000w into smaller gearmotors. Even the larger ones like the BMC or MAC, 2000w better be for short intervals.

Using 2000w and efficiency in the same sentence is a bit amusing. But along the lines of "it depends" a very large motor can run very efficeint at 2000w. But a small motor with little copper and small magnets pushed to 2000w is very likely running in very inefficiently.

Looks to me like we got another one that wants to have his cake and eat it too. A Mac or BMC run at closer to 1000w is likely to be the best way to get close to what you want. The smaller gearmotors will fry with more than 1000w if you keep it up for long.

Any motor can be ridden in a way that's efficeint, or inefficient. By pedaling with the motor off, some call a gearmotor more efficient. I don't consider this efficiency myself. I just call it pedaling without a motor. A fussy point, but off isn't efficient, its just off. So if you pedal a gearmotor with it off 25% of the time, you will use 25% less wh.
 
I tested motors for climb ~150meters hill.
Geared mid-drive: 11.23 wt/h
Torque DD: 13.53 wt/h
Speed DD: 16.48 wt/h

so, yes geared is super efficiency motor.
 
iperov said:
I tested motors for climb ~150meters hill.
Geared mid-drive: 11.23 wt/h
Torque DD: 13.53 wt/h
Speed DD: 16.48 wt/h

so, yes geared is super efficiency motor.
Click to expand...

And how long did each motor take to reach the top of the hill ? (* seconds ?)

also, what speed were they able to sustain going up at those power levels ?
 
the point being that if the DD used 16wh, while the geared used 11, did the DD make it up the hill faster ?.. if so , it also plays a factor in the motor efficiency.

if they all took exactly the same amount of time to reach the finish line (* and i'm sure it's not the case ) , it would be a true reflection .
 
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