Plug and charge - a seamless charging experience.

21 JULY 2022 • 7 MIN READ

Grzegorz Bar



Plug and charge

In the last few years, there have been plenty of ameliorations introduced to ease the EV charging experience. Whether it’s hardware or software, major changes for the better can be observed even in places where eMobility does not have its wings spread with a full potential. Yet, even the major progress in EV charging technology, doesn’t stop frequent comparisons to what it looks like with maintaining an ICE car, which tends to be described as less complicated and simply easier.

Luckily, this view is being gradually changed by technologies implemented into the world of EV charging. In this article, we’ll take a closer look at one of the most promising charging-simplifying facilities.

Plug and charge - what is it?

In short, it’s a technology that allows for an EV charging event without the necessity of additional means, such as RFID cards or apps. With Plug and Charge, the data exchange between a charger and an electric vehicle occurs entirely automatically. This includes the authentication and authorization processes. It makes the charging process much more convenient for drivers. They don’t have to worry about connecting their vehicle to the charger or starting the charging process manually. In addition, Plug and Charge also offers improved security, as the data exchange between charger and vehicle is encrypted. It makes an EV charging experience more similar to fueling an ICE car, which does not require a sequence of minor actions to authorize a charging session.

How does it work?

The technology behind Plug and Charge is based on the ISO 15118 standard. This standard defines the communication protocols and data formats that are necessary for an automated, interoperable charging process (more about it in the next section).

In order to use Plug and Charge, an electric vehicle must be equipped with a so-called Charging Control Unit (CCU). The CCU is the interface between the vehicle and the charging station. It manages the data exchange with the charger and controls the charging process. What must be remembered is that plug and charge facilitates the communication between all parties involved in the charging process, that is:

  • electric vehicle
  • charging point
  • EMP

In simple words, with Plug and Charge compatible devices, the EV contains provisioning certificate and contract certificate (between the driver and EMP) and charging station contains EVSE certificate.User is identified by the ID called E-Mobility Account Identifier (eMAID) stored in the contract certificate. eMAID is also known to the eMSP for billing purposes. Thanks to that, eMSP knows which user has to be charged for the transaction started automatically just by plugging the cable. The moment an EV cable is plugged into the socket, the charging station identifies the car's certificates and vice versa.

When plugging in at a Plug and Charge enabled charger, the CCU will automatically initiate the data exchange with the charger. This includes exchanging information about the maximum current that can be drawn, the maximum voltage that can be applied, and the plug type.

Based on this information, the charger will adapt its settings accordingly. Once the connection is established, the charger will start supplying electrical energy to the vehicle. The entire process happens automatically and doesn’t require any interaction from the driver.

ISO 15118

ISO 15118 is a joint venture of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) and one of a group of standards for electric vehicles. It describes the communication between a vehicle and a charging point. It has few use cases and Plug and charge is one of them.

ISO 15118 use cases:

  • plug and charge
  • V2G
  • RFID based authorization
  • smart charging
  • cable charging
  • induction charging

Whole ISO 15118 is built upon Public Key Infrastructure. In Plug and Charge - The EV has the contract certificate stored (X.509 certificate). The certificate associates the end-user with the public key. Because the certificate is issued by a trusted Certificate Authority, the charging station is able to check it, and if it’s valid, the charging station believes that the user presented in the certificate is not fake. The standard ensures high security of the data exchange amongst all involved parties. The security is provided via authenticity (the verification of certificates) and confidentiality (data exchange happening via encrypted channels).

As it rapidly gains popularity amongst eMobility-related operators, ISO 15118 can be deemed one of the crucial means in ensuring the seamless operation in the world of EV charging.

In terms of its other use cases, we dive deeper into the smart charging and V2G functionalities and importance in our recent downloadable guide HERE.

Open Plug and Charge Protocol

OPCP is an open standard launched by Hubject. The launch of OPCP simplifies the process of adopting the Plug and Charge technology for developers and eMobility stakeholders looking to deliver the best solutions for EV users. Standardization of said technology is a great step towards increased interoperability and unification across the industry.

Being an open protocol, OPCP gives everyone interested the opportunity to utilize Plug and Charge technology. As stated by Hubject:

“This measure is particularly relevant because the rapidly growing market for Plug&Charge results in a range of very different processes from different manufacturers. After all, unhindered access without lock-in effects will be an essential criterion for Charging Station Operators and Mobility Service Providers, offering charging solutions. In addition, qualities such as the simple and secure authentication methods for different applications and the option for further joint development in cross-sector mode are convincing. Furthermore, the opportunity for multi-contract handling is given. Multiroot handling is also implemented and compliant with ISO15118-20.”

The protocol is constantly being developed and Hubject invites any feedback and improvement ideas.

OPCP is in productive use since 2019 and is gaining more and more users amongst Charge Point Operators, eMobility Service Providers and OEMs.

It’s to no surprise, as the launch of OPCP opens the door for many to enjoy the benefits of the technology., making the charging experience a lot more effortless for the end-customers - EV drivers.

The protocol covers the following use-cases:

  • independent Service Operation:
  • RCP Service (Root Certificate Pool: used for communication between the Root Certificate Pool and the various Certificate Authorities of ISO 15118 participants (V2G, OEM, MO, CPS)
  • PCP Service (The Provisioning Certificate Pool: providing interfaces to exchange Provisioning Certificates between OEMs and MOs)
  • CPS Service (Certificate Provisioning Service: providing interfaces for generating and signing contract data of MOs)
  • CCP Service (Contract Certificate Pool: stores the signed contract data from the MOs, and provides it for the CPOs and OEMs backend)
  • PKI Authorities
  • Authentication Method
  • Role specific authentication
  • Multiple Contracts (EMAIDs) for one Vehicle (PCID)
  • Standardized Event Service
  • Interoperability between Ecosystems, V2G Root Operators etc
  • Multi Root -> CertificateSigningCertificate ability
  • Pool collaboration
  • ISO15118-20 prepared (separate Namespace already in account)