36V Hub vs 26V Crank

[brucehawsker]

I tried in an earlier thread and confused everyone, sorry. Can I start again:

In the real world, would one expect a 36V 17AH Hub motor bike to go further than a 26V 18Ah crank?

How far in each case - modest Doreset hill, 14stone bloke?

After say 20 miles on each, would the bloke tipically feel tireder on the Hub or the Crank bike?

Thank you for bearing with me......

 

[Caph]

Given that 17Ah is more or less equal to 18Ah I guess you are asking which can be the most efficient a hub motor or a crank motor? Is that right?

As I understand it the crank motor can be more efficient than the hub motor if ridden optimally due to it being able to use the bikes gears rather than the being restricted to orbital gears like the hub motor.

To be honest, I don't think there is a lot in it at the low power levels and high levels of efficiency that we have ultimately ended up with on electrically powered bicycles and so I don't really think your question is of much importance. I think a far more important question is what you prefer as your riding style, crank motor or hub motor.

Why do you ask the question?

EDIT: I'm guessing you are 14 stone, live in Dorset and are trying to decide between two bikes, one crank powered 26V 18Ah and one hub powered 36V 17Ah. Am I in the right ball park? If so, try them both and go with whichever you prefer the feel of. I have a very powerful 36V bike and a much less powerful 24V bike and I much prefer my 24V bike. It's very much a personal preference. My advice is forget about what is best in theory or on paper and get on the thing. You'll know instantly which one you prefer.

 

[NRG]

Here goes....very unscientific....Wisper 905 City vs E motion Cross. Stated ranges (yeah I know but this is for fun ) according to the Onbike web site is 20-50 miles for both.

The 905 has a 14Ah/37v battery or 518Wh, average quoted distance is 35Miles or 14.8Wh / Mile. Increasing the battery to 17Ah @ 37v = 629Wh, average distance is now 42.5 Miles

The Cross has a 10Ah/26v battery of 260Wh, average is again 35miles or 7.4Wh / Mile. Increase the battery to 18Ah @ 26v = 468Wh, so average distance increases to 63.2 Miles

So the Panasonic has the potential to go futher

 

[Caph]

Why do you ask the question?

I've just read your other thread and I can see you purely interested in the theory. To be honest, I don't think there is much in it and what little there is will be outweighed by inaccuracies in postulation and riding technique. I'm afraid my conclusion lies in pointlessness.

 

[brucehawsker]

Hi Caph,

Thank you for your honest response. In one sense my interest is theoretical - in another sense I am trying to push (help) people to make the right decsion when it comes to choosing the right bike for them.

There are other threads which have said that ALL that matters is the WattHourage of the battery. I sort of know, having tried the bikes, that this is not the case. A Panasonic Crank 26V feels (perception) as exciting as a Wisper (36V Hub). And anecdote says in the real world it goes as far and that in practice the best determinant for range is AmpHourage, Thus a 26V 10Ah crank goes as well and as far as 36V 10Ah hub. Now, if this is true, the law of conservation of energy means (i think) the guinea pig has to be putting more work into the Crank.

But many prospective e bike purchasers genuinely want to know how far the bike will go in the real world. Looking at the manufacturer literature is a murky art at best.

So I would really value people's answers to my questions posted above... Thank you so much.

 

[Blew it]

Additional to NRG's post:

Average over two years with 36 volt hub motored machines, mostly 255 rpm Bafangs, in a moderately hilly area, 13 watt-hours per mile.

Average over 200 miles with a 26 volt centre drive ( Panasonic ) in the same area, 5.4 watt-hours per mile.

The reasons for the difference in average consumtions are already well documented. The Panasonic system only adds power to the human effort of each pedal stroke, in other words, it is a true 'bionic' system.

The three freewheels incorporated into the Panasonic system means there is no drag whatsoever during each 'null' at the bottom of each pedal stroke. In fact, it is very difficult to tell if the motor is assisting or not, partly because the Panasonic system is so quiet.

In terms of human effort, a twenty mile ride is no more tiring with the center drive than with a hub motored machine.

 

[eddieo]

Being a throttle jockey for 2 years, I never thought the Panasonic system would appeal to me...But after two brief test rides last week I have now changed my mind and will investigate further.

You really need to try one, I would be surprised if you come away unimpressed. I also think hub motors are probably wasteful in their power delivery in comparison. The crank system just feels less raw and more sophisticated.

 

[daniel.weck]

Average over two years with 36 volt hub motored machines, mostly 255 rpm Bafangs, in a moderately hilly area, 13 watt-hours per mile.

Average over 200 miles with a 26 volt centre drive ( Panasonic ) in the same area, 5.4 watt-hours per mile.

With my 250W Suzhou Bafang / 8-Fun (255rpm max), running on a 16" wheel ==> 7-9 Wh/km (11-14 Wh/mile). This includes a fair amount of hill climbing.

I'm using the Tongxin now, so hopefully the consumption figures should come down.

 

[NRG]

Average over two years with 36 volt hub motored machines, mostly 255 rpm Bafangs, in a moderately hilly area, 13 watt-hours per mile.

Average over 200 miles with a 26 volt centre drive ( Panasonic ) in the same area, 5.4 watt-hours per mile.

The reasons for the difference in average consumtions are already well documented. The Panasonic system only adds power to the human effort of each pedal stroke, in other words, it is a true 'bionic' system.

The three freewheels incorporated into the Panasonic system means there is no drag whatsoever during each 'null' at the bottom of each pedal stroke. In fact, it is very difficult to tell if the motor is assisting or not, partly because the Panasonic system is so quiet.

In terms of human effort, a twenty mile ride is no more tiring with the center drive than with a hub motored machine.

Ah, real world figures thanks for that Blew it....so I wasn't too far out in post #3

 

[flecc]

In terms of human effort, a twenty mile ride is no more tiring with the center drive than with a hub motored machine.

Although I agree with everything else in your post, I have to disagree with this bit since you were speaking of the Panasonic system.

That demands a proportion of effort comes from the rider in order to get motor power, in practice according to model, series and power mode selected that's between 40 and 66%.

Very many hub motor bikes demand less rider effort, and in a more extreme case, I can take any eZee Quando made up to 2009 on a twenty mile road trip in most areas of this country and never pedal once, not even for setting off.
.

 

[HarryB]

The panasonics are always more efficient as has been said before - they demand your input whereas generally with hub motors your input is irrelevant.

Here are some real life figures dug out from the Ching challenge showing the sort of Wh per mile you get with hub motors in hilly areas. They are in the 16-20Wh per mile region but not all hub motored systems are equal and (from memory) I think the tonxin motors came in at around 9 Wh per mile which would get it close to the panasonic figure. So we can be pretty sure that, to answer your first question, it would be the 18Ah 26V Kalkhoff (especially if left unmodified) that would go further but you could well be a little sweatier!

http://www.pedelecs.co.uk/forum/electric-bicycles/4610-ching-challenge.html?highlight=ching

PS just done a back of the envelop calculation and found that my Emotion comes in at 10Wh per mile and the Cytronex comes it at 9Wh per mile for a not that hilly journey into work. Higher average speeds on the Emotion though and I am hotter when I arrive. It does show you that a hub motored bike can be pretty efficient.

 

[flecc]

From a 10 Ah battery on a Panasonic powered standard Kalkoff I got 35 miles with ease and showed that 50 miles was also possible by switching off on odd occasions when the going was very easy. Others also have shown that, and A to B recorded 46 miles without ever turning the power right off.

It follows that with an 18 Ah battery, over 60 miles should be easy and 90 miles possible without much difficulty for me. I don't know of any standard hub motor bike that could give that for me in my seventies.

As others have said, the Panasonic system wins for efficiency, though a select few of the best hub motor systems can get close if carefully used.
.

 

[Tim]

It follows that with an 18 Ah battery, over 60 miles should be easy and 90 miles possible without much difficulty for me.

Kalkhoff are quoting 140 km or 87 miles range per charge in 1:1 assistance mode with a total weight of 110kg.

They quote 60 km or 37 miles at 20mph for their Sport models in 1:2 assistance mode.

 

[Bandit]

As others have said, the Panasonic system wins for efficiency, though a select few of the best hub motor systems can get close if carefully used.
.

That was certainly our experience when trialling both types over the course of a few months in our very hilly area. Despite being harder to explain, the Panasonic system seemed to require much less thought to operate "efficiently" than a hub motored bike (once you have mastered the counter-intuitive need to change up rather than down when you want more help from the motor). To climb a steep hill with the hub motored bike (an EZee sprint) we found that as well as pedalling harder (duh!) you seemed to do better by laying off maximum throttle use (which if true is even more counter-intuitive!).

 

[flecc]

To climb a steep hill with the hub motored bike (an EZee sprint) we found that as well as pedalling harder (duh!) you seemed to do better by laying off maximum throttle use (which if true is even more counter-intuitive!).

That can happen when the battery cells are struggling to maintain the current needed with full throttle. The cells temporarily chemically tire and the motor starts flagging on the reducing current.

Using a bit less throttle within the cells capability to deliver can give a better consistency of motor output.
.