Battery life v Weight and Terrain

[Deleted member 4366]

Going real slow on a hub motor is wasteful as the majority of the electrical energy is converted to heat...

No it doesn't. It depends which hub-motor you have. What you can't have with a hub-motor is high speed and efficiency at low speed, but many hub-motors are efficient at low speed. maybe your old 24v Urban mover was crap, but don't judge all hub-motors from that. a lot has changed since you bought it all those years ago. have you tried one of those old Powabyke Euros with the lead batteries? They climb like a goat. You don't even have to pedal. They were rated at 200W. What's more, they have/had considerable more climbing torque and probably efficiency too than the 24v Panasonic crank-drives of the time. Should we therefore say that crank drives are no good at climbing?

 

[Danidl]

No it doesn't. It depends which hub-motor you have. What you can't have with a hub-motor is high speed and efficiency at low speed, but many hub-motors are efficient at low speed. maybe your old 24v Urban mover was crap, but don't judge all hub-motors from that. a lot has changed since you bought it all those years ago. have you tried one of those old Powabyke Euros with the lead batteries? They climb like a goat. You don't even have to pedal. They were rated at 200W. What's more, they have/had considerable more climbing torque and probably efficiency too than the 24v Panasonic crank-drives of the time. Should we therefore say that crank drives are no good at climbing?

What you mean UrbanMover "was",? it still is and it's ears would be burning with embarrassment, if it could hear me singing it's praises. It has small wheels and is pretty nifty on the local steep slope up from the road. It only wants a fresher battery and it will be good for another decade. I think, that it has only the 200w motor cannot confirm as the websites refer to a different product now..It came with the NimH 8amp26v pack, typical of the era, but since replaced. Little amount of rust, so good stainless steel in parts. It's a dinky little bike, limited range but good fun. Unfortunately as a folder, it's a bit cramped.

Can we agree that a hub motor, irrespective of power rating has a specific speed at which it is most efficient and at lower speeds will be somewhat lower efficiency. ?Can we agree that because the hub is directly coupled to the wheel and tyre that that translates to an optimal road speed for that motor on that wheel.?
Similarly a crank motor has a speed at which it's efficiency is peaked. But and this the crucial difference, because the crank is connected by a chain, and the possibility of gears, there is no such limitation on road speed. This means that massively low ratio gears can be fitted so that they can go up walls (exaggeration)., Slowly.!!!

 

[anotherkiwi]

Potato salad?

Pasta salad!

 

[anotherkiwi]

...
Similarly a crank motor has a speed at which it's efficiency is peaked. But and this the crucial difference, because the crank is connected by a chain, and the possibility of gears, there is no such limitation on road speed. This means that massively low ratio gears can be fitted so that they can go up walls (exaggeration)., Slowly.!!!

My experience with 32:34 is coherent with http://www.bikecalc.com/speed_at_cadence and gives between 9 and 10 km/h at cadence, seated, on a hill with +10% gradients the motor drawing less than 200 W most of the way!

Air resistance: 2.9 W/km for the Quest(!) @ 40 km/h I am guessing that more than compensates for the extra weight of the vélomobile but it does only weigh as much as many e-bikes on the market.

The new 1.4 kg xiongda coupled with a pinion C1.9xr correctly geared would take care of the weight on the hills, a 3 speed derailleur/freewheel combination with 18, 22 and 26 teeth would expand the already good 569% range quite handily! Imagine a motor + gearbox weighing about 3.8 kg (including freewheel)...

 

[Deleted member 4366]

What you mean UrbanMover "was",? it still is and it's ears would be burning with embarrassment, if it could hear me singing it's praises. It has small wheels and is pretty nifty on the local steep slope up from the road. It only wants a fresher battery and it will be good for another decade. I think, that it has only the 200w motor cannot confirm as the websites refer to a different product now..It came with the NimH 8amp26v pack, typical of the era, but since replaced. Little amount of rust, so good stainless steel in parts. It's a dinky little bike, limited range but good fun. Unfortunately as a folder, it's a bit cramped.

Can we agree that a hub motor, irrespective of power rating has a specific speed at which it is most efficient and at lower speeds will be somewhat lower efficiency. ?Can we agree that because the hub is directly coupled to the wheel and tyre that that translates to an optimal road speed for that motor on that wheel.?
Similarly a crank motor has a speed at which it's efficiency is peaked. But and this the crucial difference, because the crank is connected by a chain, and the possibility of gears, there is no such limitation on road speed. This means that massively low ratio gears can be fitted so that they can go up walls (exaggeration)., Slowly.!!!

That's all correct, though the words you used could be a bit misleading to some. All motors have a speed at which they're most efficient, but the efficiency curve is broad, so you can deviate a lot from the optimum efficiency speed without it making much difference. Here's a graph of an Ezee motor running with 15 amps. Look at the efficiency curve. efficiency is above 60% all the way from 5mph to 32 mph and above 70% from 9 mph to 31 mph.

 

[Danidl]

My experience with 32:34 is coherent with http://www.bikecalc.com/speed_at_cadence and gives between 9 and 10 km/h at cadence, seated, on a hill with +10% gradients the motor drawing less than 200 W most of the way!

Air resistance: 2.9 W/km for the Quest(!) @ 40 km/h I am guessing that more than compensates for the extra weight of the vélomobile but it does only weigh as much as many e-bikes on the market.

The new 1.4 kg xiongda coupled with a pinion C1.9xr correctly geared would take care of the weight on the hills, a 3 speed derailleur/freewheel combination with 18, 22 and 26 teeth would expand the already good 569% range quite handily! Imagine a motor + gearbox weighing about 3.8 kg (including freewheel)...

.. just curious but where do you get that wind loss figure?

 

[Danidl]

That's all correct, though the words you used could be a bit misleading to some. All motors have a speed at which they're most efficient, but the efficiency curve is broad, so you can deviate a lot from the optimum efficiency speed without it making much difference. Here's a graph of an Ezee motor running with 15 amps. Look at the efficiency curve. efficiency is above 60% all the way from 5mph to 32 mph and above 70% from 9 mph to 31 mph.

Fair enough.
On an allied topic do you have information on the improvements to efficiency of brushless motors in ebikes by advances in controller design. Just curious, What I have in mind is whether it would be advantageous to dynamically increase or decrease the voltage from the battery by incorporating a smpsu into the controller. Similar tricks were done in some class d audio amplifiers in the past.

 

[EddiePJ]

This means that massively low ratio gears can be fitted so that they can go up walls (exaggeration)., Slowly.!!!

Exactly, as my climb today shows.

https://www.strava.com/activities/1086419096/shareable_images/map_based?hl=en-US&v=1500217799

https://www.relive.cc/view/1086419096

And in relation to the battery, it was changed at about the 8.5 mile point of the climb. It isn't worth trying to climb/ use the battery once the battery level reaches one bar remaining. The power tails off too much, and it doesn't become a viable option. I also noted, just as I did last year when I completed the same climb, that the battery case becomes uncomfortably warm to the touch

 

[Woosh]

Here's a graph of an Ezee motor running with 15 amps. Look at the efficiency curve. efficiency is above 60% all the way from 5mph to 32 mph and above 70% from 9 mph to 31 mph.

are you sure?
why is it that I thought the Ezee motor has a noload speed at about 26-27mph?

 

[anotherkiwi]

.. just curious but where do you get that wind loss figure?

This guy over on ES ran a Quest model through his aerodynamics software I think? He did the Elf and his own two designs too.

https://endless-sphere.com/forums/viewtopic.php?f=28&t=62827&sid=99cc54764ea3deb3e1a5e60eaa5e6415&start=275

 

[Deleted member 4366]

Fair enough.
On an allied topic do you have information on the improvements to efficiency of brushless motors in ebikes by advances in controller design. Just curious, What I have in mind is whether it would be advantageous to dynamically increase or decrease the voltage from the battery by incorporating a smpsu into the controller. Similar tricks were done in some class d audio amplifiers in the past.

I think motor efficiency depends more on the laminations connecting the magnets and how it's wound. There's some tricks you can do with the timing, like running VVT in a car, that can get more speed out of the motor than it would normally give, but that's all beyond my working knowledge.

Somebody on ES came up with something that could change the timing on the fly recently (a couple of months ago). I can't remember the details, but it didn't get a massive response.

 

[Deleted member 4366]

are you sure?
why is it that I thought the Ezee motor has a noload speed at about 26-27mph?

There's loads of different Ezee motors including a cassette one now.

 

[Danidl]

Exactly, as my climb today shows.

https://www.strava.com/activities/1086419096/shareable_images/map_based?hl=en-US&v=1500217799

https://www.relive.cc/view/1086419096

And in relation to the battery, it was changed at about the 8.5 mile point of the climb. It isn't worth trying to climb/ use the battery once the battery level reaches one bar remaining. The power tails off too much, and it doesn't become a viable option. I also noted, just as I did last year when I completed the same climb, that the battery case becomes uncomfortably warm to the touch

.. that looked exciting, I'm not into MTB , but that could tempt me...!

 

[Danidl]

I think motor efficiency depends more on the laminations connecting the magnets and how it's wound. There's some tricks you can do with the timing, like running VVT in a car, that can get more speed out of the motor than it would normally give, but that's all beyond my working knowledge.

Somebody on ES came up with something that could change the timing on the fly recently (a couple of months ago). I can't remember the details, but it didn't get a massive response.

I came accross some postings somewhere about having multiple windings in each of the coils and then switching them from series to parallel,depending on the speed , giving the effect of low speed and high speed windings as required. That is an innovation which would increase the efficiency band for hubs.
I can't imagine much more being done with laminations. They have been optimising the magnetic paths for100 years. .. but then I have been proved wrong before.

 

[Deleted member 4366]

That's switching the windings from delta to wye. They do that it some large traction motors. It's often discussed, but nobody uses it. It might be because the wiring and switching is too complicated for an e-bike, but i guess it's because it doesn't really work at our power levels.

 

[Cyclezee]

are you sure?
why is it that I thought the Ezee motor has a noload speed at about 26-27mph?

Just for fun, I reset the CA and raised the speed limit on a bike I have with a 5 year old V2 eZee 250RPM front wheel motor with the standard eZee 20amp controller at 48v.
I did a static test to see what the max no load speed was and got 34.1 MPH, yes that's MPH not Km/h.
Of course I would only ever ride this on my private estate where the public has no access


There are several variants of the eZee V2 motor i.e. front or rear, 200, 250, 300 and 350 RPM and of course the higher the RPM the lower the torque.

The eZee motor is a fantastic piece of kit used in several applications, not just electric bikes Germany's top selling cargo bikes and trikes use the eZee kits to haul loads in excess of 300Kg and sell them all over Europe, Spain's Batec Mobility use them in their handcycles.

 

[Woosh]

Just for fun, I reset the CA and raised the speed limit on a bike I have with a 5 year old V2 eZee 250RPM front wheel motor with the standard eZee 20amp controller at 48v.

I was thinking about 36V.

 

[Cyclezee]

I was thinking about 36V.

The same set up at 36v gives no load speed of 27.4MPH so your initial estimate was very close.

 

[Danidl]

That's switching the windings from delta to wye. They do that it some large traction motors. It's often discussed, but nobody uses it. It might be because the wiring and switching is too complicated for an e-bike, but i guess it's because it doesn't really work at our power levels.

.. could be , I hadn't thought of that

That's switching the windings from delta to wye. They do that it some large traction motors. It's often discussed, but nobody uses it. It might be because the wiring and switching is too complicated for an e-bike, but i guess it's because it doesn't really work at our power levels.

Could be a y delta, didn't think about that, I thought it was more about switching parallel coils into series, in each of the 3 phases, anyway just a thought in passing.

 

[egroover]

I've got a Crossfire-e and I'm 100kg. I can ride a flattish circular route with 1 big hill and a few smaller ones, which is 45 miles in length, and I return with about 20% battery remaining. At all times I am in the lowest setting (eco/camel). Sometimes I am peddling on the flat over the 15.5mph therefore I am using no battery, but it's all comfortable going. I consider myself to be reasonably cycle fit, in that I can ride a hybrid non powered bike for 45-55 miles in a day (up to 6-7 hours rides).
So, certainly the claimed 60 mile range of the Crossfire-e is definitely realistic possibility, and not far off the mark if you are like me (maybe that remaining 20% could get me another 10 miles as it drops off when near empty)
For the record, I run narrowish (700c x 35) Energizer tyres at about 80 psi, which might roll a bit better than the wider stock Kenda tyres