Are your EV charging solutions interoperable – or are you out?

Marc Mültin
Marc Mültin
December 14, 2021
• Updated
min read
Are your EV charging solutions interoperable – or are you out?

EV charging is evolving rapidly therefore its important to ensure you have a future-proof solution.

Electric vehicle (EV) charging is growing at an exponential rate, placing greater emphasis on the software that underpins the user experience. Over the next decade, the competitive advantage in the EV charging space will be increasingly software driven. Given that the mass market for EVs is around the corner, we must make sure that the software is ready to guarantee a seamless charging experience. 

In this article, you’ll get a short overview of the currently available charging standards, we’ll talk about the one with the biggest chances of success, and explain why it’s so important to bring mature software solutions to market. I’ll let you in on the biggest hurdles we’re currently facing and also present to you a solution called JOSEV that will help us get there quicker. Oh, and for those who wonder where Tesla might be headed regarding ISO 15118, I have some news for you, too.

The hardware issues for EV chargers are mostly solved

Software has transformed many industries in the past and Covid has accelerated that trend massively. One example are traditional banks: with a huge network of physical branches they were able to offer customer service to both young and old. But as soon as the lockdowns kicked in, the management teams of high-street banks quickly realised that the only way to keep business going is through their banking websites or apps. This was an uncomfortable truth for many banks as their online service was often subpar. They needed to up their game and make their services way more accessible and easy to use, especially for the non-tech savvy elderly people, if they wanted to retain their business. 

We can draw an analogy to the EV charging industry. For the past decade, this was a pure early adopter market. More often than not, EV drivers could call themselves lucky if they a) found a charging station on their way and b) one that actually works. Whether it was a hardware or software failure, the end result was a stranded, frustrated EV driver. Not really great to get the market up and running …

Now, fast-forward to 2021, the market of EV and charging stations manufacturers got a lot busier. We finally seem to have a wide array of options, both in terms of EVs for a variety of budgets and tastes as well as reliable and fast charging stations. The initial hardware issues are mostly solved and the Combined Charging System (CCS) has become the dominant standard. CCS specifies the hardware interfaces (e.g. plugs, sockets, vehicle inlet interfaces, power classes) for both AC charging and DC charging of up to 350 kW. CharIN, the organisation behind CCS, is currently also defining a Megawatt Charging System (MCS), which will allow heavy duty vehicles and also ships, for example, to be charged with power in the megawatt range. As you can see, CCS is one standard for all kinds of EVs, be it cars, motorbikes, buses, trucks, ships, or even (small) airplanes.

Source: Based on Enel X

CCS comes in two flavours, one for single-phase electricity grids like in North America (aka Combo1 or CCS1) and one for three-phase grids like in Europe (aka Combo2 or CCS2). Aside from CCS there is also the Japanese CHAdeMO standard with a huge installation base of CHAdeMO charging stations in many countries. However, its installation base is quickly losing ground to the dramatically growing number of CCS chargers worldwide. Nissan, the car manufacturer that basically helped make CHAdeMO mainstream since 2012, announced last year that they’ll stop producing CHAdeMO EVs for the North American and European market. Their next EV model will be the CCS-based Ariya.

China, on the other hand, has developed its own charging standard called GB/T, but this one is only relevant if you produce EVs and chargers for the Chinese market. 

And last but not least, there’s Tesla. While it made a lot of sense for Tesla to build their own closed system to get the market up and running, the tectonic market plates have shifted a lot since they first started out. Even though we may still be two to three years away from a mass market for EVs, the market in general became way more mature and charging station operators need to earn money with their infrastructure. Tesla recently announced that they are opening their charging network to other CCS-based electric cars for the first time with a pilot program in the Netherlands. Also, during the latest CharIN Testival (see further down for more details) in Newark, California this November, a Tesla engineer told me that they’ll eventually implement ISO 15118, the communication standard behind CCS that enables seamless charging. Although he wasn’t able (or allowed) to let me in on a more detailed timeframe, this is great news for the e-mobility industry in terms of interoperability!

Getting the hardware issues solved is a necessary first step to enter the mass-market. Thanks to the ever growing charging station networks of IONITY, Gridserve, Electrify America, Allego, and EnBW Hypernetz, to name just the biggest ones, long-distance traveling with EVs is becoming really convenient. With the recent announcement from Stellantis, there’s going to be a new (big) kid on the block that will spice things up even more. I’m sure by 2025 at the latest no-one in their sane minds will buy a gasoline car. Simply from an economical standpoint it won’t make any sense, both in terms of total cost of ownership and capital expense. The battery prices will drop below a level that will make EVs the more affordable, more fun, and - lastly but most importantly - more environmentally friendly choice. The climate clock is ticking loudly, and it’s already 10 minutes past 12 …

Let’s focus on software interoperability to make charging a truly seamless experience

Let’s get to the nitty gritty of this article: software interoperability. What do I actually mean by that?

Remember the Combined Charging System (CCS) I mentioned above? The future-proof communication protocol behind CCS (and the new MCS) is called ISO 15118. In a nutshell, ISO 15118 is an international standard that describes how the EV and the charging station need to communicate with each other to enable a truly seamless charging experience. That seamless experience is commonly referred to as Plug & Charge. Actually, ISO 15118 is about so much more than just Plug & Charge. For example, it also enables the EV to act as a power bank on wheels, we call this feature Vehicle-to-Grid (V2G). See this article on V2G services for more information. V2G enables a smarter way of charging an EV, one that makes sure we can charge (and discharge) the EV’s battery in a way that helps the energy grid to remain in a stable state instead of EVs becoming a burden to the grid. The best part? We can even do so by making use of excess renewable energy that would otherwise go to waste. Here’s an interesting, recent article telling the story of wind farms getting paid nearly £2m to switch off – even as customers face soaring energy bills. This bizarre scenario can lead to situations where energy prices fall below zero, so you even get paid to use electricity – or feed energy back to the grid when needed. Either through your (costly) stationary battery at home or … your mobile battery aka electric vehicle sitting in your garage. This is not science fiction. Big car manufacturers like Volkswagen are committed to make this a reality from 2022 on. Have a look at VW's announcement from December 15, specifically the section on "Thinking beyond the car". Innovative energy providers like Octopus Energy already provide energy tariffs to incentivise a more flexible energy usage through variable tariffs that reflect wholesale prices.

OK, I’m getting a bit carried away with all the benefits ISO 15118 can unlock, so let’s get back to the point. 

ISO 15118 is actually a family of standards (more details here) with the most important part being ISO 15118-2. That’s the document that describes all the messages the EV and charger need to exchange, from starting a charging session to exchanging the charging parameters and controlling the energy flow to successfully stopping the charging session. If you want to dive deeper into the topic, I can recommend the ISO 15118 Manual. There’s also a free extract available to get a taste of the content.

To make the charging process of an EV a truly seamless experience, every manufacturer of EVs and charging stations must correctly implement this protocol. This means that they need to make sure that their software conforms to the hundreds of technical requirements defined in ISO 15118-2. If the implementation of every vendor conforms to the official standard, then this automatically guarantees interoperability among all vendors, which is key for user acceptance and economies of scale. At the same time, this also poses a major technical challenge due to the huge number of different implementations, individual use cases, and requirements on a diverse global market.

To ease the interoperability testing and bring everyone in the e-mobility industry together, CharIN decided to organise the CharIN Testivals. Actually, the very first interoperability testing event was organised back in 2014 by the founders of Verisco. In 2019, CharIN took over organising these two day hands-on testing events during which software engineers dig deep into implementing and testing their solutions for interoperability. It’s also a great networking opportunity with international technology experts in the smart charging communication community. 

These CharIN Testivals take place three times a year, alternating between the three key regions North America, Europe, and Asia. The last event took place mid-November this year in Newark, California, hosted by Lucid Motors. Here is a short video showing the highlights, as well as some pictures showcasing some of the EVs and chargers on site. 

On CharIN's website, you can find more images from this event.

By the way, one piece of advice before you attend those Testivals: check your implementation with one of the CCS test system providers to make the most out of your testing experience. Comemso, Verisco, and Keysight Technologies are your go-to providers for interoperability testing. They put in the hard work to implement all the happy flow and unhappy flow test cases that uncover any issues with your ISO 15118 implementation. The Korea Electrotechnology Research Institute (KERI) and DEKRA are now also the first two test houses officially appointed by CharIN as recognised test laboratories.

Instead of reinventing the wheel, let’s innovate based on a bulletproof foundation

These hands-on testing events are for me the most exciting industry happenings. This is the moment of truth (in contrast to the shiny marketing communications), here you can see the latest state of the art. I have been at every one of these 13 Testivals so far. As it turns out, after all these years there are still massive interoperability issues. Yes, the standard itself is not perfect and does come with some degree of ambiguity, which is part of the reason for non-interoperable implementations. However, we see a repeating pattern of faulty implementation issues, some of which could easily be avoided if the software engineers would actually read the specs properly. I’m not sure if it’s due to a lack of resources and rushed implementations, or a complete lack of a QA team or both. Here are some examples: 

  • Sending (or accepting) messages in the wrong sequence, although ISO 15118-2 clearly defines the sequence of messages
  • Timing requirements being ignored, which instantly lead to a communication session failure
  • Wrong response codes being sent, which inevitably leads to an instant shutdown of the communication
  • Conditional optionality: some message parameters seem to be optional at first sight, but certain requirements define that some parameters are only optional under specific conditions. A thorough study of the specification could avoid such errors.

Plug & Charge has a huge potential to get petrol heads to shift over to EVs – but we need to make the experience AT LEAST as seamless as refuelling a gasoline or diesel car at a gas station. Think about it: at a gas station, you put the nozzle into your car and then wait for minutes until the tank is full. With Plug & Charge, you can plug in the charging cable and instantly walk away to either go to the bathroom, get a coffee, or maybe go to a book shop (Gridserve forecourts are a great example) to beat the time until the battery is fully charged. BUT … the EV driver needs to be sure that the charging process will be successful. Anything below 100% interoperability is hardly acceptable, and this industry still has a long way to go to get there. If you had a gadget that only works 80% of the time, you’d probably not use it anymore after a short while, would you? 

A major reason for why we’re facing the same implementation issues over and over again is the fact that many vendors are basically trying to reinvent the wheel. EV charging station manufacturers are experts in hardware, but rarely in software. 

As a charging station manufacturer, you need to ask yourself this question: which part of your technology is going to be a commodity, and should be bought, and which innovations are the differentiators between you and your competition?

We at Switch believe that it’s tough enough for charger manufacturers to stay on top of the game and comply with ever-evolving regulations and communication standards. You shouldn’t have to worry about setting up a big team of software engineers to implement a standard like ISO 15118 and constantly worry about interoperability testing as the standard evolves. Your money is better spent on the innovations (your USP) that set you apart from your competitors. 

When pitching a business plan to investors, you also don’t go and implement your own version of PowerPoint first, do you? 

A unified operating system for all Type 2 and CCS-based chargers is available - it’s called Josev

As a co-author of ISO 15118 and author of the ISO 15118 Manual, I know the standard inside out. I know how confusing and tiring it can be to read and fully understand a standard as complex as ISO 15118-2 (I fell asleep more than once when I started getting into it 12 years ago). But I mastered it and used my knowledge to train other companies around the globe to better understand the implications of this future-proof technology to their business. After five years of consultancy, I decided to take matters into my own hands. So I started Switch and hired a great team of hand-picked engineers to help me build a single operating system for all CCS-based EV chargers. The result is Josev, the Joint Operating System of EV chargers. It’s meant to be a flexible, bulletproof foundation for EV charger manufacturers to go and build innovative solutions on top of it.

It completely takes away the software risks, significantly lowers your implementation costs, and accelerates your route to market – from 2 years of implementation and testing (yourself) to just one month of integration (with Switch). We not only take care of the communication with the EV (via ISO 15118) but also to the back office system in the cloud (via OCPP 2.0.1) – with lifetime support from the co-authors of these standards.

JOSEV will also come pre-installed on our own charge communication controller soon, reducing the integration effort even more. In case you’d like to learn more, send us an email at Together, we can create the ultimate charging experience for EV drivers and accelerate the transition to a sustainable transport.

Marc Mültin
Marc, the Founder and CEO of Switch, has over 13 years of experience in the e-mobility space and holds a PhD in Computer Science. He is the leading global expert and co-author of international EV communication standards (ISO 15118 & OCPP 2.0.1) that underpin the Switch platform.
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