Introducing DC fast charging

In DC fast charging, the charger that converts AC to DC is outside the vehicle. With some exceptions of fast AC chargers, this is the fastest way to charge an electric vehicle (EV).

DC charging is also known as Mode 4 charging. Next to Tesla’s proprietary Supercharging interface, there are three main DC charging systems. I’ll describe them below.

After that I will touch upon vehicle grid integration / interaction and standardization, as well as DC fastcharge implications and opportunities for DIY projects.

CHAdeMO

In 2005, the research and development for CHAdeMO started. It originated in Japan and has a wide coverage there. Main drivers/adopters are Nissan, Mitsubishi and Kia. Leading car at the moment is the Nissan Leaf.

“CHAdeMO” is an abbreviation of “CHArge de MOve” or “charge for moving”. The original Japanese is a play on words of “O cha demo ikaga desuka”, meaning “Let’s have a tea while charging”.

The charging standard itself is a closed standard only available to paying members. However in 2010 it was included in the IEC61851-23 (charging systems) and IEC61851-24 (digital communication for DC charging) standards. In the IEC standard CHAdeMO is defined as ‘System A’.

CHAdeMO logo
The CHAdeMO logo means smiles which associate a bright future and happiness with a combination of the circuit symbol of battery representing “Charge”, and a dynamic curving line
representing “Move”.

The CHAdeMO connector only supports DC charging so a car needs to have another socket for AC charging.

CHAdeMO socket and plug
CHAdeMO charge plug

There are various version of the protocol version starting at 0.9, then 1.0, 1.1, 1.2, 2.0 and recently 3.0. One of CHAdeMO the principles for evolution is backwards compatibility.

CAN communication

Communication between the vehicle and the charger for parameters relevant for a safe and reliable charging process are exchanged via CAN-BUS. Protocol 2.0B is used at 500 kbps with a message cycle/speed rate of 100 ms.

Charging power

The maximum charging power on one hand depends on the protocol version used.

CHAdeMO backward compatible

On the other hand it also depends on the battery voltage of the electric vehicle. For CHAdeMO 0.9, 1.0 and 1.1 the max current of 125A is leading. So for most vehicles this means around 45 kW. However in DIY conversions with lower pack voltage obviously this is less.

The maximum power of the 1.1 protocol and upwards are only relevant for vehicles with large battery packs operating at high voltages such as trucks, buses, etcetera. At that point all kinds of other aspects such as charge cable temperature monitor and cooling come into play.

CHAdeMO DIY?

Implementing CHAdeMO fast charging in do-it-yourself EV conversion is doable. The main challenge is that the protocol is not open source making it difficult to develop and implement a solution that works flawlessly. More info in the “CHAdeMO fast charging in DIY” blogpost.

GB/T 20234

Originating from China and widely adopted there. Often referred to as GB/T but in full it is the GB/T 20234 with various parts. GB/T 20234.3-2011 is specifically for the DC charging connectors. It’s very similar to CHAdeMO but not the same. It’s also using CAN communication and the 2.0B protocol but the bus speed is lower, 250 kbps. The message cycle/speed rate depends on the data element. For example 10 ms for stopping commands and 1s for battery temperature with various other ones in between. In the IEC standard GB/T is defined as ‘System B’.

GB/T vehicle connector
GB/T socket

Furthermore like CHAdeMO, the GB/T protocol has a separate plug for DC and AC. AC charging is another GB/T standard, the 20234.3-2011 with a connector that is derived from the European AC plug (the IEC 62196 standard).

The maximum power for GB/T is 185 kW (250 Amps at 750 Volts).

CCS Combo

The full name is Combined Charging System. As the name implies the CCS Combo plug supports both AC and DC charging. It originated from German car manufacturers (Audi, BMW, Daimler, Porsche and Volkswagen) and in the US Ford and General Motors.

Currently the CharIN association is developing and establishing the Combined Charging System (CCS).

DC fast charging EVSE

There were already two standards for AC charging:

  • Type 1 in North America under the SAE J1772 standard
  • Type 2 in Europe under the IEC 62196-2 standard

Therefore when combining AC and DC charging, also two CCS Combo plugs emerged. One combining Type 1 with DC and another one for Type 2. In the IEC standard GB/T is defined as ‘System C’.

CCS Combo 1

CCS Combo1 1

CCS Combo 2

CCS Combo2 1

The maximum power has increased over the years. Initially it was max 75kW (@600V) for Combo 1 and max. 200 kW (@1000V) for Combo 2 but currently up to 350 kW (400 A at 900V) is available.

Communication between car and charger

CCS uses PLC communication, which is digital communication via powerline. In this case, powerline means the control pilot / ground circuit, not the high voltage power lines. The CCS combo standard adopted the HomePlug Green Phy standard (for in-home smart grid powerline communications) as the communication protocol.

CCS Combo DIY?

Implementing CCS Combo fast charging in do-it-yourself EV conversion is a bit more challenging. While it is an open standard, the PLC communication is not trivial. However solutions for the DIY scene are starting to emerge. More info in the “CCS Combo fastcharge in DIY” blogpost.

Vehicle-grid-integration (VGI or V2G / V2X)

While moving into a more sustainable energy era, vehicle to grid is seen as an enabler for coping with the challenges when it comes to matching energy supply and demand. While you can quickly ramp up and down a gas power plant to respond to changes in energy demand, this is hardly possible with renewable energy resources.

A vehicle grid integration is in short bidrectional charging. So not only using power from the grid to charge a battery, but also use the energy stored in a battery and discharge it into the net. Especially DC charging is suitable for facilitating this since it requires the off-board charger to be bidirectional. In case of AC based V2G it would require chargers installed in vehicles to be bidirectional.

V2G (to grid), V2H (to home), V2B (to building)

The bidirectional integration could be implemented at multiple levels. To grid (V2G) where the battery is discharging into the net, but also on smaller scales such as to home (V2H) or to buildings (V2B). In that case while combining with for example solar or wind, houses or even villages could be self-sufficient.

V2G protocols

CHAdeMO already supports bidirectional charging and CCS is expecting to support it from 2025 onwards.

V2G in DIY?

Personally I’m not sure whether vehicle to grid is going to be very popular and widely adopted among EV drivers. Who is going to risk the possible battery degradation or reduced state of charge when you need the car? Perhaps if there is an incentive it might work. I think this is particularly true for do-it-yourself EV conversions where the battery often is the main investment for a project.

For energy storage solutions it is a different story though. I can imagine DIY powerwalls using second-life batteries from production EV’s becoming big.

Standardization?

With the different protocols that emerged, an interesting question is, will there be one dominating standard? From the below graph (courtesy of ABB, source: Presentation on EV Infrastructure by Cristian Martin (ABB Chile), June 2019 we can see a shift towards CCS.

Car and protocol overview ABB

CCS emerges as leading standard in Europe and US

Tesla had chosen CCS in their Model 3 and even manufacturers that were part of the early days of CHAdeMO like Kia have switched to CCS. So in 2020 only Nissan and Mitshubishi were still using CHAdeMO in their European and US models. However since the newly announced Nissan Ariya also has CCS instead of CHAdeMO it seems CCS will be the leading standard.

This does not imply that all CHAdeMO chargers will be gone soon, but I do expect in Europe and the US in the end only the CCS charging infrastructure will improve.

Any future for CHAdeMO?

What does that mean for CHAdeMO? At the moment (September 2020) there are 32.300 CHAdeMO chargers worldwide. About 50% in Europe and the remaining distributed 1/3 each over North America, Asia and Japan. I think the whole EV community, including the CHAdeMO association saw this one coming. Recently (June 2020) the CHAdeMO 3.0 or ChaoJi development update was announced. CHAdeMO teamed up with the China Electricity Council. The payoff for the ChaoJi Standard is “Faster, Safer, and Compatible to All”. While it is yet another physical connector they are looking for ways to still make it backward compatible with at least CHAdeMO and GB/T and possibly even CCS by the use of adapters. It is summarized in these two sheets in the “Update on the ChaoJi Project and the way forward”.

Status of charging standards
CHAdeMO and GBT moving into ChaoJi

With CHAdeMO and GB/T moving into ChaoJi the coverage multiplies. Already in 2018 there were 127.434 GB/T charging stations according to the China Electric Vehicle Charging Infrastructure Promotion Alliance (source: ‘Plug wars: the battle for electric car supremacy‘, Reuters).

Due to the differences in the communication protocol and other parameters making ChaoJi into the ‘grand overall standard’ might be a challenge. In the presentation “A Unified Future-Oriented Charging Programme” a deep-dive on the technical side of ChaoJi, they have ideas on all kinds of adapters, though.

Implications for DIY

Despite the ChaoJi / CHAdeMO 3.0 development I think the main protocol for Europe and the US will be CCS. So for now CHAdeMO still is a great solution for DIY, but in the end we are probably better off with CCS. Keep an eye on my blogposts!

Blog series on DC fast charging

  1. DC fast charging, an introduction
  2. CHAdeMO fast charging in DIY
  3. CCS Combo fastcharge in DIY

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