Magnet free Motors (Mahle) and Sodium Ion Batteries (CATL)

John (High Voltage)

This is the first post for myself on the new High Voltage blog and it covers two topics which I think are exciting and push the boundaries of electrical vehicle technology. Not really in terms of power and speed, but potentially in terms of the sustainability of the industry. 

The first is concerning a newly developed motor that does away with using permanent magnets and using contactless induction coils to induce the electromagnetic field in the rotor. This is not new technology however it is being pushed by a fairly large scale manufacturer called Mahle. Older induction technologies have issues with efficiency and were nowhere near as effective as rare earth magnet based motors.

The new traction motor from MAHLE is wear-free, compact, and not dependent on rare earth elements.

Based on the claims made by Mahle they seem to believe they have solved many of the engineering challenges and are making the rather bullish claim of a scalable motor that can be operated at efficiencies that exceed 95%. Which is pretty remarkable.

Mahle states “The new electric motor is also characterized by a high degree of durability, because the necessary transmission of electrical currents between the rotating and stationary parts inside the motor takes place without contact and is therefore wear-free. This makes the engine maintenance-free and suitable for a wide range of applications.”

I am not keen on the words “game changer”. I think that it gets used far too frequently and often should at minimum have the word “POTENTIAL” in capitals after it. But I am excited by this one. As said earlier it is not 100% new technology but rather it seems that Mahle has used modern engineering to overcome some of the efficiency limitations discovered previously.

An alternating field is converted to a direct current for the magnetic coils.

As Mahle points out in their video rare earth magnets are expensive materially, environmentally and geopolitically. So I can see the appeal of a motor that does not need them and can be made to operate with high efficiency with cheaper metals. This reduces the impact of resource demand shocks on Mahles ability to manufacture motors, reduces the environmental cost and reduces the cost to the consumer.

This is the kind of development that you see at Tesla where they identify a production or resource bottleneck 10 or 15 years ahead and take industry leading steps to address it. 

The motor uses an excitation coil inside the rotor which replaces the magnets. The use AC current which is converted and transmitted wirelessly into the coils in the magnets. The video here is Mahles own promotional material. Potentially this field will give a greater degree of control over the motor as it can be minutely varied whereas a magnet carries the field it was manufactured with.

Mahle claims to be able to scale the motor from compact models right the way up to larger models for things like trucks. 

This is definitely a technology I will be watching for. If we are to successfully transition to an electric based vehicle future making more efficient and sensible uses of our resources will be critical!

CATL are a major supplier to Tesla.

The second development area which I am excited about is the Sodium Ion battery which has recently had a big boost in its development and commercial realization. I think that all of the major players realize that lithium ion cells, although excellent for their energy density, come at a high environmental cost and that even expanded lithium mining and manufacturing probably will not be enough to meet our future energy demands. Tesla are well aware of this which is why they are pushing so hard at efficiency improvements in manufacturing and mining / use of raw materials.

Lithium mine

Sodium ion batteries should in theory cost many many times less than lithium ion cells. Perhaps up to 100 times less. Sodium is an extremely common element found over the entire earth's surface and carries with it a massively reduced extraction cost to lithium. Another significant theoretical advantage is the potential for a significantly faster charge rate several times beyond that of lithium.

There are significant challenges in the utilization of sodium ion batteries since the technology was first looked at in the 1970s. Several engineering challenges meant that lithium ion became the predominant technology. The first being that the sodium ions stick with the anode side during discharge. This essentially puts a severe limitation on the number of charges and discharges possible.

Probably the main restriction was sodium being less energy dense than lithium. The batteries essentially would be too heavy to be used effectively in transportation.

A power storage bank. An area ripe for exploitation for CATL sodium ion cells.

It is now 2021 and Chinese company CATL is launching a commercial sodium ion battery. These guys are a supplier for Tesla so this is not a small operation. I could not locate any specifics but it would appear that they have an engineering solution for the issue of limited charge cycles.

From what I could also read they are looking to take market share and compete initially with the lead acid battery market. This suggests to me that less progress has been made with regards to the energy density problem of sodium ion cells. It is a brilliant idea to take on the lead acid market as these cells are not known for being lightweight. So there are huge markets in the solar storage market that can be tapped even if not for Light electric vehicles yet. 

It is not surprising that China is pushing this technology though. They simply have to in my opinion. They have to electrify and use renewables as we all will and the supply of power from which can be intermittent. So if they can develop cheap banks of large scale sodium ion batteries to store power that is a huge win. If they can further refine the technology to take on lithium ion for energy density then even more opportunity. The makers recognize that there is a way to go before this technology is being used commercially to power vehicles. But the potential is there. 

Right now China imports over 70% of its lithium. They have limitless Sodium. It's a shame that most of the drive from this is coming from a drive to reduce geopolitical tension rather than to decarbonize the world. It might however just manage to do both.

Hope you like the first ever blog post by me! Feel free to have a chat about it online on the Discord server. I will try and remember to setup a chat room for the blog! 

Cheers