ISO 15118, Authocharge, and Plug & Charge

ISO 15118 enables communication between the EV and the Charge Controller beyond basic charging. It provides the foundation for features such as Plug & Charge and also enables the vehicle identification used by Autocharge.

This page explains the concepts, the relevant configuration, and what operators can expect during charging sessions.

1 Concepts

Feature	What it does	Main purpose
# ISO 15118	Enables advanced communication between the EV and Charge Controller	Foundation for Plug & Charge and other vehicle communication
# Autocharge	Automatically identifies a compatible EV and uses that identity for authorization	Simple automatic authorization without certificates
# Plug & Charge	Automatically authenticates the EV using certificates	Standardized automatic authorization
# Basic charging	Charges without ISO 15118 communication	Standard charging and fallback

1.1 ISO 15118

Aspect	Details
# What it is	Communication standard between the EV and Charging Station
# When it is used	When the EV and Charging Station support ISO 15118 communication
# What the Charging Station does	Establishes advanced communication and exchanges information beyond basic charging
# What to know	ISO 15118 support does not mean Plug & Charge is being used

1.2 Autocharge

Aspect	Details
# What it is	Automatic authorization using the EV’s Autocharge ID
# When it is used	When Autocharge is enabled and the EV provides a usable Autocharge ID
# What the Charging Station does	Identifies the EV and uses its Autocharge ID for authorization
# What to know	Autocharge is separate from Plug & Charge and does not use Plug & Charge certificates

1.3 Plug & Charge

Aspect	Details
# What it is	Certificate-based automatic authorization defined by ISO 15118
# When it is used	When Plug & Charge is enabled and the EV, Charging Station, certificates, backend, and charging service are compatible
# What the Charging Station does	Receives the EV’s Plug & Charge identity and forwards the authorization request to the backend
# What to know	ISO 15118 communication can succeed even when Plug & Charge later fails

1.4 Basic charging

Aspect	Details
# What it is	Default charging mode according to IEC 61851
# When it is used	During standard charging and as the fallback for ISO 15118, Autocharge, and Plug & Charge
# What the Charging Station does	Starts and manages the charging session
# What to know	Another configured authorization method may still be required before charging starts

2 Configuration parameters at a glance

All ISO 15118, Autocharge, and Plug & Charge settings are available under Authorization > ISO 15118 Configuration.

Parameter	Applies to	Values	Info
# Mode for ISO 15118 vehicle communication	ISO 15118 Plug & Charge	Off On (With PlugNCharge) On (No PlugNCharge)	Enables ISO 15118 communication and determines whether Plug & Charge is supported. Use On (With PlugNCharge) when Plug & Charge is required.
# ISO 15118 Vehicle Detection Time [s]	ISO 15118	Numeric default: 7	Defines how long the Charge Controller waits for compatible vehicle communication before fallback. Longer values can improve compatibility with slower EVs but increase the wait before fallback.
# ISO 15118 Connection Security	ISO 15118 Plug & Charge	Standard All ciphers	Controls accepted TLS versions and ciphers. Use Standard; use All ciphers only for compatibility issues.
# ISO 15118 Diagnostic Logging	ISO 15118	Off On	Creates the detailed 15118_log.csv communication log. Normally only required for troubleshooting or support.
# ISO15118 Session Info via OCPP DataTransfer		Off On	Sends ISO 15118 session and transaction information to the backend for correlating vehicle, charging, and backend sessions.
# Autocharge Authorization	Autocharge	Off On On (Fixed ID)	Enables Autocharge authorization. On (Fixed ID) additionally provides a fallback ID if the vehicle's Autocharge ID cannot be obtained.
# Fixed ID for Autocharge (Fallback)		Identifier	Defines the authorization ID used when the vehicle's Autocharge ID cannot be obtained.
# Autocharge ID Prefix		String e.g. BENDER-	Adds a prefix to the vehicle's Autocharge ID to make Autocharge authorizations easier to identify and manage in the backend.

info

Some Autocharge settings are only shown when they are relevant:

• Autocharge ID Prefix is shown when Autocharge Authorization is set to On or On (Fixed ID).
• Fixed ID for Autocharge (Fallback) is shown when Autocharge Authorization is set to On (Fixed ID).

2.1 Vehicle detection time and delay behavior

The ISO 15118 vehicle detection time setting defines how long the Charge Controller waits for ISO 15118 communication after plug-in.

• Default: 7 seconds
• Configurable by the operator
• Applies to every charging session

important

Even if a vehicle does not support ISO 15118, the system always waits for the configured detection time before starting charging.

2.2 OCPP DataTransfer

ISO 15118 exposes additional session and vehicle information through OCPP.

OCPP interface	Key / information	Purpose
# DataTransfer	ISO 15118 session ID Transaction ID EV identifier Charging Station identifier	Correlate the ISO 15118 session with the backend transaction
# StatusNotification	Energy amount	Reports the energy amount provided or updated by the EV
# StatusNotification	Departure time	Reports the departure time provided or updated by the EV
# GetConfiguration	EAmount	Read the latest energy amount
# GetConfiguration	DepartureTime	Read the latest departure time
# GetConfiguration	EVMACAddr	Read the EV's Autocharge ID

DataTransfer session information is sent when ISO15118 Session Info via OCPP DataTransfer is enabled.

3 Autocharge

Autocharge is the simpler, lower-cost alternative to Plug & Charge. It is not standardized like Plug & Charge; instead, the Charge Controller identifies the vehicle using an EV-provided identifier and uses that for authorization. It does not use certificate-based authentication, making it easier and cheaper to deploy, but less secure.

3.1 Configuration

Parameter	Location in Config UI	Values	Info
# Autocharge Authorization	Authorization > ISO 15118 Configuration	Off On On (Fixed ID)	Enables Autocharge authorization. On (Fixed ID) additionally provides a fallback ID if the vehicle's Autocharge ID cannot be obtained.
# Fixed ID for Autocharge (Fallback)		Identifier	Defines the authorization ID used when the vehicle's Autocharge ID cannot be obtained.
# Autocharge ID Prefix		String e.g. BENDER-	Adds a prefix to the vehicle's Autocharge ID to make Autocharge authorizations easier to identify and manage in the backend. Example: RFID- to distinguish RFID-based Autocharge IDs.

info

Some Autocharge settings are only shown when they are relevant:

• Autocharge ID Prefix is shown when Autocharge Authorization is set to On or On (Fixed ID).
• Fixed ID for Autocharge (Fallback) is shown when Autocharge Authorization is set to On (Fixed ID).

3.2 How Autocharge sessions behave

When Autocharge is enabled, the Charge Controller attempts to identify the connected EV and use that identity for authorization.

For operator-facing behavior, use the system boundary they actually interact with:

1. The EV establishes a connection with the Charging Station.
2. The Charging Station identifies the EV using its Autocharge ID.
3. The Charging Station sends the Autocharge ID to the configured authorization source.
4. The authorization source accepts or rejects the ID.
5. If authorization succeeds, the Charging Station starts the charging session.

The authorization source can be:

• An OCPP backend
• A local whitelist
• An Energy Manager

3.3 Fixed-ID fallback

With Autocharge Authorization = On (Fixed ID), the controller first attempts regular Autocharge identification.

If that identity cannot be obtained, the configured Fixed ID for Autocharge (Fallback) is used for the authorization request instead.

This is useful for environments such as company fleets where charging should still be authorized even if individual vehicle identification is unavailable.

3.4 Vehicle identity is not guaranteed to remain stable

Autocharge relies on an identifier provided by the EV.

Some vehicle manufacturers change or randomize this identifier for privacy reasons. Such vehicles may therefore:

• Work inconsistently with Autocharge.
• Appear as a different vehicle later.
• Not be suitable for Autocharge at all.

Do not treat an Autocharge ID as a universally permanent vehicle identifier.

4 Plug & Charge

4.1 Prerequisites

Plug & Charge requires certificates issued by an OCPP Backend. Refer to your Backend provider for more information.

4.2 Configuration

Plug & Charge is enabled through Mode for ISO 15118 vehicle communication under Authorization > ISO 15118 Configuration.

Use:

On (With PlugNCharge)

The shared ISO 15118 settings such as vehicle detection time, connection security, diagnostic logging, and OCPP DataTransfer also apply.

4.3 How Plug & Charge sessions behave

When Plug & Charge is enabled, the EV identifies itself using its contract certificate and the backend determines whether charging is authorized.

1. The EV establishes a connection with the Charging Station.
2. The EV provides its Plug & Charge identity using its contract certificate.
3. The Charging Station sends the authorization request to the OCPP backend.
4. The backend validates the Plug & Charge identity and returns the authorization result.
5. The EV and Charging Station confirm that they support a compatible charging service.
6. If authorization and service negotiation succeed, the Charging Station starts the charging session.

For Plug & Charge to succeed:

• The EV must establish ISO 15118 communication with the Charging Station.
• The EV must provide a usable Plug & Charge contract certificate.
• The backend and certificate infrastructure must be able to validate it.
• The EV and Charging Station must support a compatible charging service.

4.4 Plug & Charge service mismatch

ISO 15118 support does not guarantee that Plug & Charge can be used for the current charging service.

1. The EV establishes ISO 15118 communication with the Charging Station.
2. The Charging Station offers its available charging service.
3. The EV does not support Plug & Charge for that service, for example AC charging.
4. Service negotiation fails.
5. The Charging Station falls back to basic charging and another configured authorization method.

5 Using Plug & Charge and Autocharge together

Plug & Charge and Autocharge can both be enabled.

1. The EV establishes a connection with the Charging Station.
2. The Charging Station attempts Plug & Charge authorization first.
3. If Plug & Charge does not succeed and Autocharge is enabled, the Charging Station attempts Autocharge authorization.
4. If neither method succeeds, the session falls back to standard charging.

Result	What happens next
# Plug & Charge succeeds	The Charging Station starts the charging session.
# Plug & Charge fails and Autocharge is enabled	The Charging Station attempts Autocharge authorization.
# Plug & Charge and Autocharge both fail	The Charging Station falls back to standard charging.

6 Frequently Asked Questions

6.1 ISO 15118

• The Charging Station first attempts ISO 15118 communication. If the EV does not support it, the station waits until the configured detection time expires before falling back to basic charging.

• Possibly. Some EVs need more time to establish communication.

  Increasing the timeout can improve compatibility, but EVs that do not support ISO 15118 will also wait longer before fallback.

• Depending on the EV, ISO 15118 can provide information such as:

  • Requested energy amount.
  • Planned departure time.

  Some EVs only provide static energy values, and state of charge is not provided during AC charging.

  If ISO15118 Session Info via OCPP DataTransfer is enabled, the Charging Station can also send session and transaction identifiers to the backend.

• The Charging Station can communicate charging limits received from the backend to the EV.

  The EV can then optimize charging within those limits using information such as required energy amount and planned departure time.

• When enabled, the Charging Station sends:

  • ISO 15118 session ID.
  • Transaction ID.
  • Vehicle identifier.
  • Charging Station identifier.

• Use Standard.

  Use All ciphers only to resolve compatibility problems with older EVs.

6.2 Autocharge

• Some EVs change or randomize the identifier used by Autocharge. If that happens, the existing whitelist or backend assignment may no longer match the EV.

• If Autocharge Authorization is set to On (Fixed ID), the Charging Station uses the configured Fixed ID for Autocharge (Fallback) for authorization instead.

  Otherwise, Autocharge cannot provide authorization and another configured authorization method is required.

• Yes. With OCPP 1.6, the complete idTag, including the prefix, is limited to 20 characters.

6.3 Plug & Charge

• The Charging Station establishes ISO 15118 communication and attempts Plug & Charge. During service negotiation, the EV rejects the AC charging service because it only supports Plug & Charge for DC charging. The Charging Station then falls back to basic charging.