EV charging: IEC 61851, ISO 15118 and OCPP conformity
Guide, EV charging
Placing an electric vehicle charger or a charging station on the global market goes through a stack of standards that govern the physical interface, the digital communication and the back-office protocol. IEC 61851 (general requirements, AC and DC) defines the charging modes, connector behaviour and the control pilot signal. ISO 15118 specifies vehicle-to-station digital communication, including Plug and Charge identity over a V2G Public Key Infrastructure and, in ISO 15118-20, bidirectional power flow for V2G or V2H. OCPP, published by the Open Charge Alliance, structures the back-office link between charging station and central system. In North America, UL 2202, UL 2231 and UL 2594 take the lead, with CTEP and NIST Handbook 44 covering weights and measures. This page maps the standards, the certification routes (CE, UL, MID), the cybersecurity layer and the recurring field pitfalls.
Institutional and normative map
Section titled “Institutional and normative map”EV charging conformity sits at the intersection of electrical safety, automotive interoperability, telecommunications and metrology. Several bodies issue the applicable rules, each with a distinct scope.
| Body | Scope | Type of output |
|---|---|---|
| IEC TC 69 | Conductive charging systems, electrical safety, EMC | IEC 61851 series, IEC 61980 (wireless), IEC 62752 (IC-CPD) |
| ISO TC 22 SC 31 | Vehicle to grid digital communication | ISO 15118 series |
| CENELEC TC 69X | European adoption (EN IEC 61851, EN ISO 15118) for CE marking | EN harmonised standards under LVD and EMC Directive |
| Open Charge Alliance | Back-office protocol, charging station to central system | OCPP 1.6, OCPP 2.0.1, OCPI for roaming |
| UL | North American product safety | UL 2202, UL 2231-1, UL 2231-2, UL 2594, UL 2750 |
| NIST and CTEP | US weights and measures for billed charging | NIST Handbook 44, California Type Evaluation Program |
| CharIN | Industry interoperability, testivals, CCS architecture | Test protocols, certification programmes for CCS, MCS, Plug and Charge |
| Hubject and other PKI operators | V2G root of trust for Plug and Charge | V2G Root CA, sub-CAs, contract certificates |
The certification plan combines mandatory regulatory frameworks (CE marking under LVD, EMC Directive and RED if Wi-Fi or cellular is embedded; UL listing in North America; MID for billing in the EU) with industry conformity (CharIN, OCA, V2G PKI) that is contractually mandatory even though not legally required.
IEC 61851, the physical and electrical foundation
Section titled “IEC 61851, the physical and electrical foundation”IEC 61851-1 edition 3 (2017) is the base reference for conductive charging systems. It defines the safety, control and physical interface requirements common to all modes.
Charging modes
Section titled “Charging modes”| Mode | Definition | Typical use |
|---|---|---|
| Mode 1 | Connection to a standard household socket, no control pilot, no protection in the cable | Two-wheelers, light vehicles in residential context, often prohibited or restricted on heavier vehicles |
| Mode 2 | Standard household socket with In-Cable Control and Protection Device (IC-CPD) per IEC 62752, control pilot in the box | Emergency cable supplied with most vehicles, up to 13 to 16 A |
| Mode 3 | Fixed AC charging station with control pilot and protections in the station | Public and home AC charging, 3.7 to 22 kW |
| Mode 4 | Off-board DC charging, charger external to the vehicle, vehicle exposes only a DC connector and a digital communication interface | DC fast and ultra-fast charging, 50 kW to 350 kW and beyond |
Mode 3 and Mode 4 are the two modes that drive most certification work for public infrastructure. Mode 2 is covered by IEC 62752 for the in-cable box itself.
Control pilot signal
Section titled “Control pilot signal”The control pilot is a PWM signal on a dedicated wire (CP) between the station and the vehicle. It carries two functions: presence detection and current capability negotiation. The duty cycle encodes the maximum current the station is willing to deliver, the voltage level encodes the vehicle state (A: not connected, B: connected, C: ready to charge, D: ready to charge with ventilation, E: error, F: station not available). The signal integrity of this PWM is a recurring source of interoperability defects: amplitude drift, slow edges, ground bounce on multi-outlet stations.
Connector types
Section titled “Connector types”| Type | Standard | Regional dominance |
|---|---|---|
| Type 1 | SAE J1772, single-phase | North America (AC) |
| Type 2 | IEC 62196-2, single or three-phase | Europe, much of Asia (AC) |
| CCS Combo 1 | IEC 62196-3, Type 1 plus DC pins | North America (DC) |
| CCS Combo 2 | IEC 62196-3, Type 2 plus DC pins | Europe (DC) |
| CHAdeMO | IEEE 2030.1.1 and IEC 61851-23 references | Japan, declining elsewhere |
| GB/T | GB/T 20234, GB/T 27930 | China |
| NACS | SAE J3400, formerly Tesla connector | North America (emerging standard) |
| MCS | Megawatt Charging System, in standardisation | Heavy duty vehicles, IEC 61851-23-3 in progress |
IEC 61851-21-2 EMC
Section titled “IEC 61851-21-2 EMC”IEC 61851-21-2 (2018) specifies EMC requirements for off-board chargers, that is the station side. It covers conducted and radiated emissions, conducted RF immunity, ESD, surge, burst, voltage dips, including specific test conditions reflecting the high power and high switching frequency of modern chargers. The vehicle side is covered by automotive EMC standards (CISPR 25, ISO 11451, ISO 11452). The two sides meet at the charging cable, where common-mode currents on the high-voltage DC bus are a known source of radiated emissions.
IEC 61851-23 for DC fast charging
Section titled “IEC 61851-23 for DC fast charging”IEC 61851-23 (2014) targets DC fast charging stations. It adds specific requirements on top of IEC 61851-1: isolation monitoring before energising the cable (Insulation Monitoring Device per IEC 61557-8), contactor welding detection, sequence of voltage rise and current ramp, cable temperature monitoring on cooled connectors above 200 A, and the test plan for the DC current control loop. Edition 2 work is in progress to align with ISO 15118-20 and high-power MCS systems. The 2014 edition remains the certification reference for most CCS chargers currently on the market.
ISO 15118, the digital communication layer
Section titled “ISO 15118, the digital communication layer”ISO 15118-2 (2014) defines the application protocol between the vehicle Electric Vehicle Communication Controller (EVCC) and the station Supply Equipment Communication Controller (SECC). It uses PowerLine Communication (PLC) over the control pilot wire (Green PHY HomePlug GP), an XML schema serialised in EXI (Efficient XML Interchange) format and a TLS 1.2 transport layer for Plug and Charge.
Plug and Charge
Section titled “Plug and Charge”Plug and Charge is the user-facing function: the driver plugs the cable in, the vehicle and the station negotiate identity and authorisation over ISO 15118-2, and the charging session starts without an RFID card, app or payment terminal interaction.
Behind that experience, four building blocks are needed.
- V2G Root CA: the root of trust of the Plug and Charge PKI. Several operators run their own V2G Root (Hubject, others) and the chains are mutually trusted via a trust list.
- Contract certificate: provisioned in the vehicle by a Mobility Operator (eMSP), tied to a billing contract.
- Charging station with TLS server certificate: signed under a sub-CA of a recognised V2G Root, and able to perform OCSP checks on the contract certificate.
- Certificate Provisioning Service (CPS): back-office service for installing, updating and revoking contract certificates.
A failure on any of the four (expired root, wrongly-signed sub-CA, certificate chain truncated in the EXI message, OCSP server unreachable) breaks Plug and Charge silently: the user sees a session refusal without a clear error code on the dashboard. PKI hygiene is therefore a critical part of the conformity work.
ISO 15118-20 and bidirectional charging
Section titled “ISO 15118-20 and bidirectional charging”ISO 15118-20 (2022) is the successor application protocol. It introduces bidirectional energy transfer (V2G for grid services, V2H for home backup, V2L for accessory load), wireless power transfer, scheduled and dynamic charging modes, and several cybersecurity reinforcements (TLS 1.3, additional cipher suites, certificate enrolment improvements). ISO 15118-20 is intended to coexist with ISO 15118-2 for a transition period: most stations announced as bidirectional today implement ISO 15118-20 on a vehicle and station pair, while continuing to support ISO 15118-2 with other vehicles.
A bidirectional claim that is not backed by an ISO 15118-20 test campaign is a hidden non-conformity: the firmware may advertise V2G capability, but without protocol-level interop testing the safety supervision and the certificate handling have not been validated.
ISO 15118-3 physical layer
Section titled “ISO 15118-3 physical layer”ISO 15118-3 (2015) covers the PLC PHY on the control pilot, including coupling network, frequency band (1.8 to 30 MHz) and coexistence with the IEC 61851-1 PWM. Interference between the PWM duty cycle modulation and the PLC carrier is a known integration risk: poor coupling design produces bit errors on the PLC and forces the station to fall back to basic IEC 61851-1 signalling, which silently disables Plug and Charge.
OCPP, the back-office link
Section titled “OCPP, the back-office link”OCPP (Open Charge Point Protocol), published by the Open Charge Alliance, is the protocol between a charging station (Charge Point) and the central back-office (Central System). It is independent of IEC 61851 and ISO 15118 in scope: OCPP handles operator-level functions (authorisation against a token database, transaction reporting, firmware update, configuration push) while ISO 15118 handles the local vehicle-to-station exchange.
OCPP 1.6
Section titled “OCPP 1.6”OCPP 1.6 (2017) is the de facto baseline in deployed fleets. It uses JSON over WebSocket (the SOAP variant exists but is rarely used in new deployments), supports a minimal authorisation scheme based on RFID tags, transaction start and stop messages, and basic smart charging primitives. Its security model is light: authentication is by client-side credentials in the WebSocket handshake, TLS is recommended but the standard does not enforce mutual TLS.
OCPP 2.0.1
Section titled “OCPP 2.0.1”OCPP 2.0.1 (2020) is the modern version, and the version that aligns the OCA stack with ISO 15118 and modern operator expectations.
Key additions over 1.6.
- ISO 15118 integration: tunnelling of Plug and Charge authorisation requests through OCPP, central management of contract certificates and OCSP responses.
- Smart charging v2: complete charging profile management, schedules, priorities, demand response interface.
- Device management: structured firmware update, log retrieval, diagnostics retrieval, monitoring of variables on the station.
- Display messages and tariff information: standardised display content on the station HMI.
- Reservation v2: reservation tied to user identity rather than to a connector slot.
- Three security profiles:
- Profile 1: HTTP Basic over TLS (transport encrypted, lightweight credential).
- Profile 2: HTTP Basic over TLS plus server certificate validation by the station.
- Profile 3: Mutual TLS, the station presents a client certificate signed by an operator CA.
Public procurement (Distribution System Operators in Europe, large mobility operators, public administrations) increasingly mandates OCPP 2.0.1 with Profile 2 or 3, in particular when Plug and Charge is in scope or when the charging station is connected to a distribution grid management platform.
OCPI for roaming
Section titled “OCPI for roaming”OCPI (Open Charge Point Interface) is a complementary protocol between back-offices: Charge Point Operator (CPO) to electric Mobility Service Provider (eMSP), for cross-operator roaming. OCPI does not touch the station directly, but a station deployed under a roaming agreement needs to expose OCPP fields consistent with the OCPI data model on the back-office side.
Certification routes by region
Section titled “Certification routes by region”European Union, CE marking
Section titled “European Union, CE marking”A charging station placed on the EU market typically claims conformity under:
- LVD (Low Voltage Directive 2014/35) for electrical safety, applying EN IEC 61851-1 and EN IEC 61851-23 as harmonised standards;
- EMC Directive 2014/30, applying EN IEC 61851-21-2;
- RED 2014/53 if the station embeds Wi-Fi, Bluetooth or cellular (most public chargers do, for OCPP backhaul);
- MID 2014/32 annex MI-003 if the station is used for billed energy (see MID guide);
- Machinery Directive only in edge cases (automated motorised cable management);
- RoHS 2011/65 for restricted substances.
In Germany, the additional Eichrecht layer requires a signed measurement record and a PTB type approval on the metrology chain. Most pan-European operators implement Eichrecht by default even outside Germany, to simplify their fleet.
United States and Canada
Section titled “United States and Canada”In North America, the safety listing references:
- UL 2202, Electric Vehicle Charging System Equipment, for AC and DC charging stations as system equipment;
- UL 2231-1 and UL 2231-2 for personnel protection systems for EV supply circuits;
- UL 2594, Electric Vehicle Supply Equipment, for the EVSE itself;
- UL 2750 for wireless power transfer EVSE;
- NEC Article 625 as the installation framework in the National Electrical Code.
The product carries a Nationally Recognised Testing Laboratory (NRTL) listing mark (UL, Intertek ETL, CSA). For Canada, the SCC (Standards Council of Canada) recognises NRTL certifications under the bilateral agreement, but a separate Canadian certification (CSA) is often easier for distribution.
For weights and measures in the US, billed public charging falls under state law, most states adopting NIST Handbook 44 specifications. California adds the California Type Evaluation Program (CTEP), which is the de facto reference for US public charging since California concentrates a large share of the deployed network.
Japan, China, other markets
Section titled “Japan, China, other markets”| Market | Connector | Charging standards | Certification |
|---|---|---|---|
| Japan | CHAdeMO | JEVS, IEC 61851-23 references | PSE mark, METI registration |
| China | GB/T | GB/T 20234, GB/T 27930, GB/T 18487 | CCC if applicable, China EV charging interoperability programme |
| Korea | CCS Combo 1, dual standard transitioning | KS C IEC 61851 alignment | KC mark, KATS |
| Australia | Type 2 (AC), CCS2 (DC) | AS/NZS adoptions of IEC 61851 | RCM mark |
Cybersecurity layer
Section titled “Cybersecurity layer”EV charging concentrates two distinct cybersecurity exposures: the local vehicle-to-station communication (ISO 15118 over PLC) and the back-office connection (OCPP over WAN). Both must be considered together because an attacker who compromises one side can pivot to the other.
ISO 15118-2 TLS and V2G PKI
Section titled “ISO 15118-2 TLS and V2G PKI”ISO 15118-2 mandates TLS 1.2 for Plug and Charge sessions, with cipher suites restricted to a list specified in the standard. The PKI hierarchy is:
- V2G Root CA: top of the chain, operated by a trust ecosystem (Hubject, others).
- Sub-CA: operator or manufacturer level.
- End entity certificates: station TLS certificate, vehicle OEM provisioning certificate, contract certificate.
Certificate lifecycle handling (renewal, revocation, OCSP, certificate transparency where applicable) is part of the conformity. A station that does not check OCSP because the back-office is unreachable cannot safely default to accepting the certificate: this is an integrity gap that auditors catch on Plug and Charge campaigns.
OCPP 2.0.1 security profiles
Section titled “OCPP 2.0.1 security profiles”The three security profiles (HTTP Basic over TLS, TLS plus server certificate validation, mutual TLS) define the minimum protections on the WAN link. Profile 3 (mTLS) is the recommended target for public infrastructure. Certificate enrolment on first connection (manual provisioning versus EST or SCEP) is a critical configuration decision: a fleet deployed with shared credentials cannot be revoked granularly.
Alignment with CRA and IEC 62443
Section titled “Alignment with CRA and IEC 62443”The EU CRA (Cyber Resilience Act) applies to charging stations as products with digital elements, with full obligations from December 2027. IEC 62443-4-2 is the underlying product cybersecurity reference for industrial automation, applicable by analogy to charging station controllers. The intersection of ISO 15118-2, OCPP 2.0.1 security profile and IEC 62443-4-2 is the recommended baseline for new designs. See CRA guide for the CRA scope.
Functional safety on the station and vehicle sides
Section titled “Functional safety on the station and vehicle sides”A DC fast charger has multiple safety functions that combine to prevent electric shock, fire and battery damage.
| Safety function | Reference | Typical realisation |
|---|---|---|
| Residual current detection on mains side | IEC 61851-1, RCD Type B for DC residual current | Type B RCD or equivalent monitoring (RCM-DD) |
| Isolation monitoring on DC output before contactor close | IEC 61557-8, referenced by IEC 61851-23 | IMD measuring insulation resistance, threshold typically 100 ohm per volt |
| Contactor welding detection | IEC 61851-23 | Voltage measurement across open contactor, cross-check before each session |
| Cable temperature monitoring | IEC 61851-23, cooled connector requirements | NTC sensors in the connector, current derating at threshold |
| Emergency stop | IEC 60204-1 (when applicable) | Hardwired button cutting station contactors |
| Overvoltage and overcurrent on DC output | IEC 61851-23 | Software limits plus hardware crowbar |
A SIL claim under IEC 61508 is not legally required but is often part of operator qualification packs. SIL 2 on the isolation supervision and contactor chain is a common target. On the vehicle side, ISO 26262 applies to the onboard charging controller (see ISO 26262 guide). The two safety frameworks (IEC 61508 station side, ISO 26262 vehicle side) meet at the connector and must agree on the failure detection time budget.
CharIN, testivals and interop campaigns
Section titled “CharIN, testivals and interop campaigns”CharIN (Charging Interface Initiative e.V.) is the industry association that owns the CCS architecture, the Megawatt Charging System, and many of the interop programmes for ISO 15118 and Plug and Charge.
Testivals
Section titled “Testivals”Testivals are organised interop events where vehicle manufacturers and charging station manufacturers bring equipment and execute a structured test plan. A typical testival covers:
- IEC 61851 control pilot conformity,
- ISO 15118-2 application protocol coverage,
- Plug and Charge end-to-end with multiple PKI roots,
- ISO 15118-20 sessions if applicable,
- repeated start and stop cycles, error injection, cable swap.
Passing a testival is not a formal certification but produces a participation report that operators recognise. CharIN also runs a CCS Certification Programme (CCS-Cert) for components and systems, which is closer to a formal scheme.
V2G PKI interop
Section titled “V2G PKI interop”Plug and Charge PKI operators run their own interop events: a vehicle is enrolled with a test contract certificate, plugged into stations from various manufacturers, and the certificate validation path is traced end to end. The failure modes are subtle (intermediate CA missing from the EXI chain, OCSP responder slow, clock skew on the station) and only surface in interop testing.
Step-by-step certification plan
Section titled “Step-by-step certification plan”The typical sequence for a new public DC fast charger targeting the EU and US markets.
- Freeze the architecture: connector types, output power, communication stack (IEC 61851-1 PWM, ISO 15118-2 PLC, ISO 15118-20 if bidirectional), back-office protocol (OCPP 2.0.1 with Security Profile 2 or 3).
- Map the applicable standards per target market: EN IEC 61851-1, EN IEC 61851-23, EN IEC 61851-21-2, EN ISO 15118-2 for the EU; UL 2202, UL 2231, UL 2594 for North America; GB/T for China; PSE for Japan if relevant.
- Pre-compliance EMC on conducted emissions, especially on the DC output side, before formal lab.
- Run safety lab at an accredited body: IEC 61851-1 and IEC 61851-23 test programmes, including isolation, RCD/RCM-DD, contactor welding, cable temperature.
- Run EMC lab: IEC 61851-21-2 full programme.
- Run ISO 15118 conformity: typically at a CharIN-recognised lab, then participate in at least one CharIN testival.
- Run OCPP conformity: through the Open Charge Alliance certification programme.
- Plug and Charge PKI enrolment: contract with a V2G Root operator, integrate sub-CA signing and OCSP.
- MID and Eichrecht if billed energy, through a notified body for MID and PTB for Eichrecht.
- UL listing for North America, in parallel with the EU stream.
- CTEP type evaluation if California is a target market.
- First field deployment, monitored, with a structured field issue log feeding back into the firmware lifecycle.
For cross-cutting orders of magnitude per phase, see certification timeline and certification costs.
Common pitfalls
Section titled “Common pitfalls”| Pitfall | Consequence |
|---|---|
| Control pilot PWM amplitude or timing out of IEC 61851-1 tolerance | Vehicle and station disagree on current capability, charging derated or refused |
| Insufficient pre-compliance EMC on the DC output side | Conducted emissions fail formal lab, schedule slips by weeks for redesign |
| Mode mismatch (Mode 3 station with a Mode 2 vehicle configuration, or Type 1 plug on Type 2 station) | Mechanical or electrical incompatibility, surface defect blamed on the station |
| Plug and Charge certificate chain truncated in the EXI message | TLS handshake fails, session refused without clear user feedback |
| OCSP responder unreachable, station configured to fail open | Integrity gap flagged by auditors, Plug and Charge claim refused |
| OCPP 1.6 deployed where the tender required OCPP 2.0.1 Security Profile 3 | Disqualification at procurement stage, late and costly stack rewrite |
| ISO 15118-20 firmware activated without re-running interop tests | Bidirectional sessions fail silently, energy not exported, operator credibility hit |
| Missing isolation monitoring threshold or wrong setpoint | IEC 61851-23 lab rejection, full electrical redesign |
| No CharIN testival participation | Operators refuse the charger in their qualification pack, market access blocked |
| MID and Eichrecht ignored on a public station billed by kWh | Metrology violation, legal block of the station for billed transactions |
| Vehicle ISO 26262 ASIL allocation incompatible with the station IEC 61508 SIL assumption | Safety budget mismatch at the connector, deadlock between vehicle and station OEM |
Going further
Section titled “Going further”- MID, Measuring Instruments Directive: metrology rules for billed energy in the EU
- IEC 61010, laboratory and measurement safety: related electrical safety reference for measurement devices
- ISO 26262, automotive functional safety: vehicle side functional safety, the counterpart to IEC 61508 station side
- Cyber Resilience Act: horizontal EU cybersecurity obligation for connected products
- EN 303 645, IoT cybersecurity baseline: consumer cybersecurity baseline, useful for home charging units
- Certification timeline and certification costs: cross-cutting orders of magnitude
- Glossary: definitions of EVSE, EVCC, SECC, V2G, V2H, Plug and Charge, OCPP, OCPI
See also
Section titled “See also”- Solar PV modules: IEC 61730 safety and IEC 61215 performance
- EN 50128 and EN 50657: railway software assurance
- DO-178C and DO-254: avionics software and hardware
- DO-326A and ED-202A: avionics cybersecurity airworthiness
- MIL-STD-461 and MIL-STD-464, defense EMC standards
Sources and references
Section titled “Sources and references”Sources & references
- IEC 61851-1, Electric vehicle conductive charging system, Part 1: General requirements , IEC webstore.iec.ch/publication/33644
- IEC 61851-23, DC electric vehicle charging station , IEC webstore.iec.ch/publication/6588
- ISO 15118 series, Vehicle to grid communication interface , ISO www.iso.org/standard/77845.html
- Open Charge Alliance, OCPP 1.6 and OCPP 2.0.1 specifications , Open Charge Alliance www.openchargealliance.org/protocols/
- UL 2202, Electric Vehicle (EV) Charging System Equipment , UL Standards www.shopulstandards.com/ProductDetail.aspx?productId=UL2202
- CharIN, Charging Interface Initiative , CharIN e.V. www.charin.global/
- NIST Handbook 44, Specifications for Weighing and Measuring Devices , NIST www.nist.gov/pml/owm/publications/handbook-44