Roaming in electric vehicle charging networks

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Traditional vehicles, with combustion engines, can be fueled at public gas stations, which are operated by a variety of networks. Drivers can freely choose a more convenient gas station to fuel their vehicle.

For electric vehicles, we will also have networks of public electric charging stations, in which drivers will be able to recharge their vehicles. However, the creation of isolated solutions for these networks can fragment the market, making life difficult for drivers.

In this article, we will discuss how Roaming, a technique traditionally used for interoperability of mobile networks, can be used to solve this problem.

Recharging in electric mobility

An electric vehicle can be recharged at charging stations, also called charging points, connected to the power grid. There are fast charging stations, which usually work with direct electric current and high power, and slow charging stations, which work with alternating current and lower power.

In a slow charging station, the recharge time of a car can reach 8 hours. This time can be reduced to something around 20 or 30 minutes in a fast charging station. Thus, slow charging stations are usually installed in places where people stay for long periods of time (such as shopping malls parking lots, businesses etc.). Fast charging stations, on the other hand, are more interesting for highways or public charging stations.

The charging process is usually self-service, that is, the drivers themselves connect their vehicles to the station and charge their car. Driver Authentication and subsequent authorization for the station to release power is often done through a smartphone application or an RFID card (radio frequency — or “contactless” — identification card) made available by the charging station operator.

The driver is charged for the energy consumed to power their vehicle, according to the conditions of the contract that they have with the charging station operator. Pricing is usually proportional to the energy consumed, but the charging company can market the charging at market prices and is not required to follow the energy tariffs of the distributors in their immediate area.

What happens if a driver that has an application or RFID card from a certain charging station network tries to recharge their vehicle at a station from another network? That is where problems begin to arise. If the networks have their own independent solutions, the driver will not be able to recharge their car in another network’s station, since they will not be recognized by the network’s authentication and charging systems. This fragmentation of the market can complicate the lives of drivers greatly.

The roles of charging companies

To better understand the problem, let’s see how companies can act in this sector. There are two different roles that companies can take on:

eMSP (Electric Mobility Service Provider)

Electric Mobility Service Providers (eMSPs) are the companies responsible for providing charging services to end users — who may be individuals or companies that own electric vehicles.

The conditions for use of the charging services — including, for example, the cost of an electrical vehicle charge — are defined in an agreement between the user and the provider of the recharge service (eMSP). The eMSP offers recharge-related services such as locating charging stations in a given geographical area, user authentication, unlocking charging stations for use and the actual charging of vehicles.

EMSPs own the customer base, but do not necessarily have their own charging station infrastructure. For this, they can count on CPOs.

CPO (Charge Point Operator)

Charge Point Operators (CPOs) are companies that typically have their own charging stations, but may also be responsible for the operation of third-party stations. CPOs are responsible for the physical installation of the network’s charging stations, as well as their operation and maintenance (O&M).

Thus, CPOs manage the physical infrastructure of charging stations, making their network of stations available to end users through one or more eMSPs.

In a charging network, there can be a variety of companies acting in the roles of eMSP and CPO, as represented by the Companies “Company A” and “Company B” in the image below. However, some companies may act as both eMSP and CPO, as illustrated by “Company C” in the diagram.



As illustrated in the image above, a user can only use the charging stations of their network, that is, user1 can only use CPO1’s charging stations, made available by eMSP1. The same limitation occurs with user2, who only has access to CPO2 stations.

If user1 also wants to access CPO2’s stations, they would have to make an additional contract with eMSP2. The increase in the number of companies operating in the charging ecosystem can further increase this fragmentation. Thus, it becomes impractical for users to have contracts with all eMSPs in the market.

Roaming in electric charging networks

In the past, telecom operators faced a problem similar to the one described above, where users registered with one phone carrier were unable to use their mobile phones outside the coverage area of their carriers. The solution was to allow users to continue to use their mobile phones, but with the telecommunications infrastructure of other phone companies.

This solution, known as roaming, depends on commercial agreements between companies, which establish the conditions and costs associated with the use of service by users with contracts with another network. The solution also requires communication protocols that allow communication between the systems of the operators for the provision of services to end users.

Roaming can be applied to the electric mobility context, allowing users to charge their vehicles using the charging infrastructure of other CPOs. The figure below illustrates a roaming scenario between electric mobility companies (Company A, B and C), established through commercial agreements and through the interconnection of company systems via communication protocols.

Roaming brings direct benefits to drivers, who can count on a wider network of charging stations. In the example above, user1 has a contract only with eMSP1, but can access the charging stations of all carriers (CPO1 and CPO2).

Roaming also brings benefits to the companies involved. For instance, CPOs may increase the use rate of their stations, as more customers will have access to their infrastructure. eMSPs, in turn, will be able to rely on a wider network of charging stations, improving services for their users and preventing them from migrating to other eMSPs.

A key step for roaming services to be adopted on a large scale by companies in the electric mobility ecosystem is defining open communication standards and protocols that can be adopted by companies to ensure interoperability between their systems.

Currently, there are several roaming-related protocols under development. Among them, Open Clearing House Protocol (OHCP), Open Interchange Protocol (OICP), eMobility Inter-operation Protocol (eMIP), Open Charge Point Interface Protocol (OCPI), in addition to IEC 63119, a standardization initiative of the International Electrotechnical Commission’s group (IEC).

Although they present different solutions, all of these standards define protocols for communication between CPOs and eMSPs, seeking to enable interoperability between different recharge networks.

The large number of roaming protocol standardization initiatives shows that the industry and standardization bodies are sensitive to the importance of the topic. On the other hand, it also shows that there is still no consensus on the best solution to be adopted.

To enable roaming, a decision of which standards and protocols are to be adopted in each region is essential. This type of selection will probably be achieved as charging solutions continue to develop and mature.


In this article, we have presented how the fragmentation of the electric vehicle charging market in independent networks can bring complications to drivers, limiting their access to only the charging stations of certain networks.

Roaming, used to allow users access to telecommunications services even outside the coverage area of their phone companies, can be an alternative to enable the interoperability of charging networks, allowing users to access charging stations that may not belong to their CPO’s network.

To enable roaming solutions, it is essential to define standards and protocols that standardize communication between the parties of the electric charging ecosystem, such as CPOs and eMSPs.

Currently, there are several standards in development, proposing different roaming solutions and protocols. It is expected that the maturity of electric mobility will promote a consolidation of the standards and protocols adopted in a given region, ensuring interoperability among charging networks and making day-to-day life of electric vehicle drivers simpler.

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