E-MobilityE-RoamingOpen StandardsOCPI

EV roaming with open standards - OCPI and OCHP

02 APRIL 2021 • 12 MIN READ

Piotr Majcher



The introduction to open standards or EV roaming - OCPI and OCHP

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In a search for interoperability, the e-mobility market players need to speak the same language. Demand for coherent infrastructure is dictated by rapid EV penetration. Several factors, such as local policies and incentives, contribute to an enthusiastic approval of electrically-powered vehicles. Hence, the focus has been transferred to the network and its ability to create open, accessible infrastructure. To match the pace - resonate with market expectations and work together to create an accessible, open environment - the new order needs EV roaming.

EV roaming is something users cannot see but witness, and whether knowingly or not, appreciate. Open standards create the road to consistent and complete e-roaming. With a large pool of contributors, up-to-date and secure solutions are available at hand to any participant in the rapidly growing e-mobility market. To understand the role of open standards in e-mobility here are explanations for widely approved models.

Note: In the e-mobility world there are four main open standards facilitating e-roaming. Two are developed and maintained by non-commercial hub operator and independent knowledge board - OCPI Open Charge Point Interface and OCHP - Open Clearing House Protocol & OCHPDirect. Two others were developed by commercial roaming hub operators. These are OICP Open InterCharge Protocol designed by Hubject and eMIP - eMobility Interoperation Protocol maintained by GIREVE.

OCPI - Open Charge Point Interface

Originally developed by eViolin, a Dutch association of Charging Station Operators and eMobility Service Providers, that pursues national roaming with international connection, using open standards. In cooperation with ElaadNL -  the knowledge and innovation center in the field of Smart Charging and the charging infrastructure in the Netherlands - major Dutch grid operators. Initially governed by the Nederlands Kennisplatform Laadinfrastructuur (NKL) - Netherlands Knowledge Platform for Public Charging Infrastructure - a partnership of business organizations, governmental figures, and research institutes. From May 2020 the OCPI is managed and maintained by the EVRoaming Foundation. Open Charge Point Interface offers p2p and any roaming hub integration business model.

OCPI is registration-free, openly available at no cost. Published under the Creative Commons Attribution-NoDerivatives 4.0 International Public License. Hence, the distribution is free when given proper credit. Although blocks the distribution of the modified versions of the protocol. The most recent version (v2.2) was released in October 2019. Open Charge Point Interface offers a modular set-up, a very convenient way of deployment - it is up to the individual decision which modules to include. It also covers a variant check, a significant factor for peer-to-peer mutuality as there is no fundamental actor applying updates or completing to support previous protocol versions.

Open Charge Point Interface is the only, so far, set on JSON/rest and is a real-time protocol. It maintains synchronous and asynchronous operations.

Open Charge Point Interface carries multiple explications for Eichrecht (German calibration law for electric vehicle charging), as recommended by the top European e-mobility providers - Has-to-be, Alfen, eBee, and Mennekes. In March 2021 EVRoaming Foundation announced the start of the first independent Roaming Agreement pool. The organization aims to support setting up trusted agreements between parties, for either p2p or via a (virtual) roaming Hub. The pool is available for all Full Contributors (The foundation distinguishes the following membership classification categories: Full Contributor, Associate Contributor, Sponsors, and Managing Contributors).

The protocol’s documentation describes market roles as follows:

  • The EV user connects to a charge point in can be provided information from the MSP
  • The e-mobility service provider (eMSP), grants EV services to EV users. eMSP connects to Charge Point Operator (CPO) to offer e-roaming services.
  • The CPO manages, maintains, and operates charge points (charge stations), on the technical and administrative side. CPO is open to connecting to MSPs to offer roaming services.
  • The e-mobility service provider ensures charge point location information.
  • The eMSP influences smart charging sessions depending on extra sources of information.

The purpose of a roaming hub is to facilitate information exchange between market players. In this division Open Charge Point Interface supports:

  • Roaming via hub - OCPI facilitates data exchange between eMSPs and CPOs via hubs, for this operation, the protocol offers a separate hub supporting module.
  • Roaming peer-to-peer (p2p) - Both eMobility Service Providers and Charge Point Operators can correlate immediately via OCPI. Separate interfaces are designed for eMSPs and CPOs.
  • Roaming with mixed roles
  • Authorization - The token module in the OCPI architecture supplies Charge Point Operators with the knowledge of any token information of eMSP. There are two ways to execute authorization, which could be real-time or via a whitelist.
  • Reservation - On the eMSP side, the OCPI offers to make and cancel a reservation.
  • Billing - OCPI supports the basis for invoicing - sending CDRs - Charge Detail Records.
  • Tariff information - The protocol supports the exchange of the key details related to energy tariffs. Complex tariff calculations depend on the time charged and energy. All this information is included in the tariff module.
  • Static charge point information - This covers: IDs, CPOs, charge point site, host, charge point name, charge point location details (name, address, geocode, type, image, platform level, directions), nearby facilities, link to a website, time zone, opening times, current availability status, scheduled availability status, accessibility, tariffs, authorization modes, payment methods, terms and conditions, charge mode, connector type, maximum power, voltage, amperage, energy mix, remote start/stop, reservation, smart charging support, and the last update mark.
  • Real-time charge point information - Stats: available, blocked, charging, inoperative, out of order, planned, removed, and reserved.
  • Session information (real-time & static) - Covers: sessions ID, start time, end time, energy consumed, CDR ID, authorization method, location, charge point ID, meter ID, currency, charging periods, total cost, sessions status, and last update. The same information can also be in real-time.
  • CDR information - CDR IDs, time, duration, finish status, and more.
  • Callibration law (Eichrecht) support - OCPI maintains the exchange of signed meter data which can be used to conform to Eichrecht - German calibration law.
  • Remote start/stop - The start and stop of any charging session can be done remotely via the eMSP app.
  • Smart charging - Several charging profiles are supported by OCPI: the cheapest charging, the fastest charging, the most environmentally-friendly charging, or no particular choices. The preferences can be registered per session by the user. The CPO can accept or decline the option. Although the smart charging profile module does provide certain options, these cannot be ensured, since other factors influence the charging session.
  • Platform monitoring

OCPI’s ultimate goal is to allow any EV driver to charge at any charging station in the EU. In fact, the protocol is used intensively throughout Europe (Netherlands, Belgium, Luxembourg, UK, Germany, France, Spain, Italy, Denmark, Austria, Poland), but not limited. It also gains recognition, among others, in the USA, Canada, South Africa, and India. The protocol is gaining acceptance in ever-widening circles and the number of countries is steadily increasing.

OCHP - Open Clearing House Protocol and OCHPDirect

OCHP is the second protocol that offers a hub or p2p connection. Integration with hubs is done via OCHP, and the direct peer-to-peer connection is possible with OCHPDirect. The solution is maintained and expanded by Smartlab Innovationsgesellschaft GmbH.

and ElaadNL (ElaadNL also supports aforementioned OCPI), organizations established by German and Dutch entities. OCHP is used by the roaming hub e-clearing.net (e-clearing.net also offers connectivity via mentioned above OCPI) operated by Smartlab and owned by Smartlab and ElaadNL. As a not-for-profit platform, the main interest of e-clearing.net is to develop the e-mobility market. Both available current versions OCHP v1.4 and OCHPDirect v0.2.6 were released in August 2016 (In October 2020 OCHP introduced to members the newest update 1.5, but no further public information was provided, the valid version remains 1.4).

The OCHP documentation is free to download and does not demand registration. Thanks to the MIT license, the protocol allows for open distribution and alteration. The administration of the OCHP lies on the Smartlab/ElaadNL side, which has the remaining right to apply and execute edits to the protocol. Prior and complete implementation testing needs to be conducted before a participant gains access to the e-clearing.net roaming platform. To support a coherent development of the OCHP protocol each year developers collect user feedback.

The Open Clearing House Protocol is based on the SOAP (Simple Object Access Protocol) computer protocol. It largely relies on asynchronous communication (opposed to real-time communications, as for OCPI). For instance, e-clearing.net does not store transaction data. Instead of real-time authentication, OCHP forms lists of users who are allowed to authenticate. This approach allows avoiding a single point of failure (SPOF) - if the roaming hub breaks down, charging sessions remain active.

The OCHP protocol documentation describes the following market roles:

  • The EV user, that has a direct or indirect contract with an eMobility Service Provider, charges an EV at a charge point/charge station.
  • The eMSP grants access to charge points/charge stations to the EV owner. The eMSP provides the EV user access via an RFID card or certificates. The service is supported by CPOs. The CPO operates charge points and acts as a contract agent for the eMSP. Each charging session is settled between the eMSP and the CPO under agreed conditions.
  • The parking spot operator (PSO) owns and operates the parking spots with access to the charging infrastructure operated by the CPO. The PSO offers a parking spot where a charge point is located and can supply information on location and availability to the CPO.
  • The clearinghouse operator (hub operator), runs a software platform to enable data exchange between MSPs, CPOs, and NSPs*.

*The documentation of OCHP protocol also distinguishes the role of the Navigation Service Provider (NSP), similar or equivalent to the role of Charge Point Operator. It applies to service towards the EV user for searching, locating, and routing to charge points. The party may have contracts with CPOs or MSPs.

Open Clearing House Protocol supports:

  • Roaming via hub - Hub’s roaming platform connects the associated partners. OCHP is used by the roaming hub e-clearing.net, but the documentation does not specify if the roaming hub should necessarily be run by e-clearing.net.
  • Authorization - EV owners are recognized by tokens. The eMSP supplies a list with contract IDs of registered EV users to the hub, that can later be downloaded by CPOs. If an EV is charged at a CPO, the operator’s system checks the ID against the roaming authorization list downloaded from the roaming hub.
  • Billing - Charge detail records (CDRs) collect charge data, hence CDRs describe the billing. The CPO exports the CDRs to the roaming hub. The hub performs a basic plausibility check. Correct CDRs are forwarded to the eMSP. In case the CDRs fail the validation of reliability check, are sent back to the CPO for the fixing. Besides, the roaming hub also archives CDRs.
  • Static charge point information - OCHP can be applied to show the charge point ID, CPO, charge point site owner, charge point location (name, address, geocode, type, image), nearby facilitates, link to a website, time zone, current status, scheduled availability status, accessibility, tariffs, authorization forms, payment options, charge mode, connector type, maximum power, guaranteed power, voltage, support phone number, reservation possibility, the maximum time for the reservation, languages of the interface, user feedback form, and the time of the last update. Besides, the tariff model can handle complex advanced tariff schemes based on time of the day, date, charged energy, charging speed, and duration based on input from CPO. The CPO supplies static charge point information to the roaming hub, which can be then processed and transferred to contracted EV owners by eMSP.
  • Real-time charge point information - OCHP provides the current status of a charge point (available, reserved, occupied, blocked, out of order, unknown). OCHP divides real-time from static data. The dynamic data is stored in a separate database, dedicated to this kind of access. Real-time charge point information is sent to the roaming hub, then is transferred to the signed users of an eMSP.
  • Session information - refers to CDR ID, charge point ID, token ID, contract ID, CDR status, start time, end time, duration, charge point address, charge point type, connector type, tariffs, meter ID, total cost, and currency.
  • Remote start/stop - Charging sessions can be controlled via an eMSP app.

The OCHPDirect (dedicated for p2p connections) supports the following functionalities:

  • Roaming peer-to-peer - Achieving e-roaming is possible without a connection with a hub.
  • Authorization - Charging sessions can be controlled via an eMSP app.
  • Real-time sessions information - Start of a charging session, end of a charging session, metering information, power management information, handy invoicing.
  • Remote start/stop - The charging process can be controlled when stationary started via the eMSP application.

E-clearing.net, unlike commercially orientated hubs, is an open platform that facilitates the exchange of roaming authorization, charge transaction, and charge point information data (all transactions are free). At the moment, e-clearing.net requires only a fee for joining the platform.

Open EV roaming charging software

Why apply at least one open standard? To save time and open your network to a larger number of users, increase opportunities and reap profits. Or, in other words, applying open EV roaming charging software protects against being excluded from the market. Both, Open Charge Point Interface and Open Clearing House Protocol & OCHPDirect are classified as stable, reliable, and secure solutions. The growing number of countries that support the development and promotion of both solutions indicate openness, independence, and royalty-freedom. Open and modern approach contributes to fast penetration and enthusiastic approval. Many countries are in the early phase of charging infrastructure development. Open standards are meant to facilitate rapid growth and ensure up-to-date functionality.

OCPI and OCHP support installing a public open charging network

Open Charge Point Interface and Open Clearing House Protocol are developed and supervised by non-commercial organizations. Demand for roaming includes cross-border connectivity. The future of the open network will largely depend on the willingness of partners to collaborate and regulatory guidance. For instance, some countries already established conditions for operation on the domestic market. Slovakia requires new parties within three months of the commissioning of the recharging points, to be connected to any roaming platform that connects more than 80 operators. In Norway, Oslo authorities formed an open policy for sharing with third parties. Berlin expects every Charge Point Operator operating a recharging point in the public domain to register it in a central authentication platform managed by the city, offering access to the customers of each eMobility Service Provider under comparable conditions. To meet the conditions, it is necessary to open a network. Following the 2050 EU strategy, soon it might be mandatory to provide seamless connection on large networks in the Union.

An extensive scientific analysis of the four most commonly developed protocols in terms of the search for the ideal protocol can be found here.