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e-Traction in cold weather in-wheel direct drive bus test; automotive in-wheel product in prototype stage

In-wheel direct drive motor company e-Traction Europe BV (earlier post) has undertaken a new development projection in cooperation with Hybricon SE to equip two Volvo 7700 city buses with a modified e-Traction system for cold-weather testing. At this time in spring in Sweden, temperatures are still well below zero, with icy road conditions throughout the day.

The Hybricon project will use an e-Traction system equipped with TheWheel SM500/3 motors. The project will test the reliability of TheWheel, the e-Traction system and Valence Li-ion batteries in extreme cold conditions; thermal functioning of the e-Traction system at cold conditions; and fuel consumption.

TheWheel SM500 line features integrated power electronics; a water-cooled electronics and motor package; and up to 11,000 N·m (8,100 lb-ft) peak torque. TheWheel SM500 has a range of subtypes available depending on its operating circumstances.

The length of the motor vary from 345mm to 555mm depending on the torque needed. The payload also can be changed by altering the bearing materials (eg. from aluminium to steel) This also changes the unit’s weight. The basic SM500/3 has a motor length of 555mm, and is targeted for heavier applications as heavy city buses, freight trucks and industrial applications (container terminal tractors).

SM470/1 for automotive applications. e-Traction is also developing an version of TheWheel targeted for light-duty automotive applications, especially city cars. n average overall driveline efficiency allows downsizing of battery capacity in the vehicle. Especially small vehicles profit from this feature, the company notes.

The SM470/1 features:

  • In-wheel direct drive with average overall efficiency of 86%;
  • 470 mm diameter, 263 mm length, 70 kg weight;
  • Integrated power electronics;
  • Integrated fluid cooling;
  • Integrated mechanic brake solution; and
  • 600 or 900 Nm torque, dependent on model.



Good idea but very low e-motor efficiency.


Hopefully they will publish low temperature data. Consumer Reports found that when they tested the Leaf in the Mid West at low temperatures the 100 mile range dropped to 19.


I could see range cut in half with low temperatures. All you have to do is insulate the battery box and warm before using and then heat from the drive circuits and motors can do the rest.


Right on SJC.


Mannstein, is this the consumer reports piece you are talking about:
'But its range is often not what its gauge might indicate. One staffer found that the range was rapidly reduced from 36 miles to barely 19 one frigid morning.'

Seems to be talking about indicated range at part charge being incorrect, not overall range. Range dropping to half under extreme conditions seems to be more typical, which is what the rest of the consumer reports piece says.

It would be more informative if people gave links for these kind of claims, and a quote.


Although E - motor specs are sometimes quoted as mid 90% efficient, one should note that overall efficiency is affected by the number and efficiency of each stage. From say grid generator thru transmission losses including voltage conversions and the neccessary rectification and voltage conversion before the battery losses can be added.
From this now mobile capacity there are more power conditioning devices ending up with the controller finally losing efficiency yet again to power electronics and motor losses.

The longer the train and the more steps - the greater the losses.

We can assume that the battery, controll and motor losses are very significant as they all require cooling strategies. Batteries with high internal resistance requiring a cooling strategy on both the charge and discharge sides.

Design constraints in this E motor may lead to higher losses but also there is mention of power electonics on board to be considered. Both motor and controll /power efficiencies are areas of constant research for efficiency improvements.

I.E. are trialling what appears a smart E- traction motor that "only" achieves 86% efficiency, they should in my opinion be applauded for breaking new ground.

Developing a concept is valuable to understand the real world constraints and identify where the greatest gains can be expected - future mass production will realise those refinements.

In a more general sense IE best guestimates,
That E - motors in tranport could suffer from well to wheel efficiency numbers in the range of ~ 5 to ten percent (solar and theoretial capacitor and other high effciency components ) up to ~ at a pinch - 30 - 40% efficient coal distribution network may seem unacceptable at first glance but one should compare the gasoline standard when it takes a gallon of gas wildy (conservative) to 'deliver' a gallon and a likely only a 15% average return from that.
Plainly a lot of energy goes into transport let alone infrastructure and medical costs that see middle class? the motoring public spending as much as 50% of average incomes in this respect.

Of course the environmental impact will cover a similarly wide range and likely considerably larger.


The E-Traction wheel motor is the quietest motor on a bus I've ever heard. There are two E-Busz buses in Rotterdam with this motor, and there is none of the usual whining of gears, humming of motors, etc. Just complete quiet because there are no gears or transaxle. All you can hear is the noise of the tires on the road. Quieter than a tram, possibly the quietest public transportation ever! Probably will need to add a "Tram bell" sound to avoid running people over.




Thank you for your real world experience, it looks like a good design.


Arnold...if you use Sun (the source of most energies) to Wheel efficiency for both ICE and electrified vehicles, one can only wonder how low the TOTAL efficiency would be in both cases.

If you add all the energy required to clean up pollutants at all stages for ICE vehicles it could be even much worse.

Some electrical power plants, such as Hydro, are very efficient and very high voltage power lines reduce lost to less than 4%. Battery charging stations, even the wireless type, can be up to 96% efficient. On board electronics will also be highly efficient. Gear less e-motors can also reach 96+%..

ICE vehicles are about 18% efficient (tank to wheels)

BEVs are up to 90% efficient (battery to wheels)

If you go any further, it does not necessarily become much better for ICE vehicles.

fred schumacher

Hub motors would allow for a complete rethinking of automotive morphology, especially for buses and trucks. It would allow for super efficient packaging, and, with trailing arm suspensions without transverse axles, low floor heights, lower height overall, and resultant reduced frontal area.

For long distance transport, human and cargo, gensets could be more perfectly isolated from the passenger compartment. In a series hybrid system with variable power requirements being buffered through the battery pack while the genset runs at steady speed, the engine could be modeled after super-efficient marine style long-stroke, slow turning diesels, or OPOC HCCI. All wheels become drivers, making for excellent traction.

If the standard semi-tractor rig is redesigned so that there is no trailer, per se, but a shipping container acting as its own trailer, grappled to the tractor's fifth wheel at the front, with a grappled on trailing axle assembly at the rear that always remains with the tractor, then hubmotors are only required by the tractor, while the trailer is an axle-less "dumb" unit.

fred schumacher

An addendum to the above on automotive morphology:

If a shipping container is not placed on a trailer, but acts as its own "trailer," the overall height of the unit can be dropped by a meter, reducing frontal area significantly. Hydraulics can be used to raise the container to dock height. When not in use, the container is simply dropped on the ground, and all wheels and axles stay with the tractor.

A system similar to this is used by some logging trucks hauling tree-length loads in northern Minnesota. The trailing axle is connected to the fifth wheel by a long tube, which collapses and rests on top of the fifth wheel when not hauling a load. When the tractor is dead-heading, there is no trailer on the road behind it.


Someone mentioned the range of a nissan leaf dropping to 19 miles in winter temps..

That seems unlikely, all winter tests i've seen show that the battery range cut is more like 1/2..

Anyhow the fault is the Leaf's battery pack. It is not designed to heat itself; which is extremely short sighted in my opinion. A car's battery pack can be heated with less than 1000 watts; less than a tenth of the energy the car uses cruising on a flat, to get 50% more battery power... !!

Why Nissan left this feature out is absolutely beyond me. Perhaps rushing the car to market to get a tax credit ?

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