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BMW, GM complete testing on DC Fast Charge station usage; validation on BMW i3 and Chevy Spark EV

Engineers from BMW AG and General Motors recently passed a milestone in the adoption of the new SAE standard for DC Fast Charging. Teams from both companies worked jointly to ensure the conformity of DC “Combo” Fast Charge stations developed by various suppliers to the SAE standard by charging pre-production versions of the BMW i3 and the Chevrolet Spark EV.

This industry-coordinated early confirmation of DC Fast Charge hardware and software will accelerate efforts to roll out SAE Combo DC Fast Charge infrastructure in the coming months. Among the suppliers who participated in the testing were ABB, Aker Wade, Eaton and IES.

Our goal with this cooperation was to ensure that DC fast charging stations be available to provide BMW i customers the premium fast charging experience in time for the arrival of the BMW i3s.

—Cliff Fietzek, Manager connected e-Mobility at BMW of North America, LLC

This unprecedented cooperation among OEMs and equipment suppliers demonstrates the maturity of this important technology that will help speed the adoption of electric vehicles around the world.

—Britta Gross, Director, Advanced Vehicle Commercialization Policy at General Motors

Just as the majority of the world’s major automakers adopted the SAE’s 120V/240V AC connector standard to assure plug-in vehicles could access all charging infrastructure regardless of vehicle make or model, auto manufacturers (including BMW, General Motors, Ford Motor Company, Chrysler, Daimler, Volkswagen, Audi and Porsche) have committed to adopting the SAE combo fast charge connector, which assures standardization of the DC Fast Charge connectors.

This new combined AC and DC charging combo connector provides added ease of use for DC Fast Charging, including a single charge port on the vehicle, and allows electricity to flow at a faster rate, making EVs more convenient to use for consumers who may not otherwise have convenient access overnight to charging at home. Using DC Fast Charging, EV owners could recharge current battery packs up to 80% in less than 20 minutes.

The first vehicles to offer the new SAE Combo DC Fast Charge connector will be the BMW i3 and the Chevrolet Spark EV. DC Fast Charge is expected to be available when the BMW i3 launches in the US.

Comments

sd

I am glad to see that SAE is showing some leadership in this and that at least BMW, General Motors, Ford Motor Company, Chrysler, Daimler, Volkswagen, Audi and Porsche are on aboard. I used to have a colleague that said that standards are great and everyone should have one and usually everyone does (a different one). The problem is making standards that make sense and can be reasonably updated to account for new technology.

HarveyD

Eventually, ultra quick DC charging of very large capacity battery packs (120++ kWh) will require temporary battery pack splitting, into 3 or 4 packs during charging. Chargers, connectors and cables would be smaller and easier top build.

Arne

HarveyD, please enlighten me on the advantages of pack splitting, as I am convinced there are none.

DaveD

Harvey,
Anne is right, dividing the battery up has no effect on how much or how fast it can take charge. I keep seeing people say things like that and I'm trying to figure out where it's coming from. Do you have a source of someone claiming it's true and why? It would be interesting to see their logic.

Dave R

Let's look at an example of how "pack splitting" may be useful, starting with a 85 kWh Model S.

Currently the Model S can charge at a maximum of 120 kW - with a pack voltage around 400V, that works out to around 300A which is the current limit of the connector. That gets you a 20-80% charge in around 30 minutes.

Now let's say you want to speed that up to 10 minutes charging at 360 kW.

One option is to increase the size of the wires to handle 900A. The problem is that to handle 300A, you already need conductors about 1/2" in diameter - that's a lot of copper and not easy to keep flexible. To handle 900A you're going to need wire about 1 1/2" in diameter. Good luck flexing that!

Another option is to increase the system voltage. If you want to triple charging rate, you're going to need to increase voltage to around 1200V. It's quite a bit more challenging to design systems which can handle those types of voltages safely compared to the current 500V rated systems. A big benefit here, though, is that for slower charge rates you can use thinner wire.

Or as Harvey suggests another option is to increase the number of plugs and split the pack up accordingly. Of course the drawbacks here are that you need additional plugs, connectors and a way to segregate the pack into multiple functional pieces, likely requiring some heavy duty contactors or electronics.

It would be very interesting to see what kinds of systems actual EV enegineers have devised...

DaveD

Dave R,
I see where you're going on the charger side. But the batteries themselves are limited by the chemistry and is not taxing the current generation of fast chargers.

I think any charger problem can be solved much more easily than the battery itself.

HarveyD

DaveR is on the right track.

Future extended range (500 miles) e-vehicles will use higher performance 180 to 200 kWh battery packs or 2X+ the Tesla S-85. Quick charging (10 minutes) those very high capacity battery packs, at 550 to 660 VDC, will require a 1200+ KW charger, a huge cable and huge connector.

The make the charger, cable and connector more practical (size wise and amperage wise) it would be easier:

1. to electronically split the 180+ kWh battery pack into 3 (60+ kWh) packs.

2. to replace the single 1200+ KW charger with 3 (400+ KW) standard chargers (*).

3. to split the huge connector into 3 in 1 connector.

4. to split the large single cable into 3 in 1 wires smaller cable.

(*) 400 KW chargers already exist and 3 of them could do the job. Using 3 mass produced 400 KW chargers could be cheaper than developing and building 1200+ KW charger.

HarveyD

Our sole Hydro/Wind clean electricity supplier wants to increase the tariff by 2% nest year to financially promote Wind energy, EVs and public/domestic charging facilities. Our pro-Oil and anti-government people are raging but keep very quiet when fossil fuel price goes up at an average of 8%/year.

I've got nothing against higher fossil fuel price per se but complaining/raging against a 2% rise for very low cost clean electricity, specially when cost of living increase is close to 2% is unreal.

DavidJ

That's an alliance of German and US car companies. In particular does not not include France and Japan and so Renault, Nissan. So by no means a unanimous consensus on standards yet.

Arne

Dave R and HarveyD,

Splitting the cable is not the same as splitting the pack!

The fundamental problem is getting a few 100 kW through a wire that can still be handled by a person. Splitting the pack does nothing to solve that fundamental problem, since you still have to transport exactly the same power.

Instead, you propose splitting the charger cable. This may solve the perceived 'handlability' problem, but that solution does in no way depend on a split pack. There is no need to have these three charger cables to connect to separate packs. You can easily merge the three 300 A currents into one 900 A and then charge one single pack.

The Tesla pack already consists of 7000 cells, organised in (iirc) 16 modules. So in essence you could say you already have a split pack. In the Tesla case, the limitation is the battery chemistry. They now charge at 1.4C, which is already above the 1C specified by Panasonic.

Tesla recently bumped the supercharger power from 90 kW to 120 kW and I suspect they first wanted some real world data on battery degradation resulting from ~1C charging before going to 1.4C.

Let's quickly forget the idea of people plugging in 3 cables to charge their cars. It is not going to happen.

Engineer-Poet

If heavy cables are too much for people to handle, heavy connectors on jointed arms with e.g. counterweights to make them easier to handle are one of several possibilities.  So are robotic connection systems; common industrial robots already have almost everything required to insert a plug with force and accuracy humans would have difficulty matching.

These "insurmountable problems" are mere molehills.

Arne

EP, And if the robotic plug comes from beneath, it can directly connect to the pack. No thick, heavy, expensive cables needed in the car.

Engineer-Poet

That runs into issues of dirt, ice and snow, but it is an out-of-the-box notion that might get somewhere.

HarveyD

How about 3 wireless chargers i.e. one charging unit for each of the three battery pack main modules? Possible but costly.

How many wheels on locomotives and heavy cargo truck trailers to split/share the load?

Electrically squeaking, you have three main choices to better manage larger loads:

1) use higher voltage (up to 1,000,000 Volts for transmission lines to reduce current (amperage) and the size of cables.

2) to split the load into 3-phases with a cable for each phase.

3) to use 4 cables for each phase to further increase capacity.

If you want ultra quick charge at 1200+ kWh rate you may have to look around and see what has been done by transmission lines people to solve similar problems?

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