Charging Session Integration

Important considerations for consistently configuring the central system and the charger to provide reliable session tracking, enabling management operations, user experience and preventing undesired outcomes.

Topics in this document:

Session Start Timeout

Please ensure to configure the session start timeout period on charger side. It covers the time available to start the session, since the acceptance of remote start request or driver authorization.

Remote session start and authorization timeout on charger side represents the time since OCPP RemoteStartTransaction/Authorization acceptance, after which session must be started. If this time is breached, the charger should prevent any session start without the next OCPP RemoteStartTransaction or Authorization operation acceptance.

To avoid fraudulent usage, we suggest using preventive measures by configuring the charger’s timeout period in which the session is expected to start. OCPP 1.6 has a ConnectionTimeOut setting, which can be used, as described below.

Charger may also have other settings which are not part of OCPP 1.6 to handle other preventive scenarios - to tackle those, please check the charger’s specific manual or consult with the manufacturer.

OCPP 1.6 requires support for ConnectionTimeOut setting: Interval in seconds from beginning of status: ‘Preparing’ until incipient Transaction is automatically canceled, due to failure of EV driver to (correctly) insert the charging cable connector(s) into the appropriate socket(s). The Charge Point SHALL go back to the original state, probably: ‘Available’.

Session timeout section is related to ready-session-expiration settings of the central system, as it closes inactive sessions based on the expiration settings and idle job configuration. Make sure to use the consistent ready-session-expiration time on the central system, so it works aligned with the charger.

Driver Authorization

As the drivers/customers who intend to charge the vehicle may use the payment types of prepaid, postpaid or pay-now, each session charging needs to be first authorized by the Tridens EV Charge’s central system to verify the driver’s fund sufficiency for beginning the charging session. Thus, charger’s local and offline authorizations lists and caches need to be disabled, to propagate all the authorizations to the central system.

Below is the list of OCPP 1.6 and OCPP 2.0.1 standardized authorization settings. Note that the chargers may have their own customized list of configuration settings, out of standardized scope. As a CPO, please review the charger specific implementation for any additional settings that need to be managed.

Configuration Attribute Name
Description
Restriction
OCPP 1.6 Variable Name
OCPP 2.0.1 Variable Name
Authorize Remote Session RequestsIndicates whether remote start requests need to be authorized by the charger before proceeding to charge.Set to true, to ensure that the session is still authorized to start.AuthorizeRemoteTxRequestsAuthorizeRemoteStart
Authorization Cache EnabledIndicates whether the charger supports the authorization cache for the driver’s identifiers.Set to false, to prevent using charger’s local authorization caches.AuthorizationCacheEnabledAuthCacheEnabled
Local Offline AuthorizationIndicates whether the charger, when offline, will start a transaction for locally authorized identifiers.Set to false, to prevent using charger’s local authorization caches.LocalAuthorizeOfflineLocalAuthorizeOffline
Allow Offline Session of Unknown DriverIndicates whether the charger allows authorizing any unknown identifiers that cannot be authorized by local authorization list or authorization cache.Set to false, to prevent any unverified sessions.AllowOfflineTxForUnknownIdOfflineTxForUnknownIdEnabled
Central Contract ValidationIndicates whether the Charge Point can provide a contract certificate that it cannot validate to the Central System for validation as part of the authorization.

Used in the scope of ISO 15118’s Plug & Charge.
Set to true, so the central system’s verification is used.CentralContractValidationAllowedCentralContractValidationAllowed
Offline Contract ValidationIndicates whether the charge point will try to validate a contract certificate when it is offline (not connected to the central system).

Used in the scope of ISO 15118’s Plug & Charge.
Set to false, so the central system’s verification is used.ContractValidationOfflineContractValidationOffline

Table: List of authorization settings to manage in OCPP 1.6 and 2.0.1.

Offline Sessions

Disable the charger to start the charging sessions without allowance of the central system, as it would result in non-customer public sessions.

Make sure to disable LocalAuthorizeOffline and AllowOfflineTxForUnknownId settings of OCPP 1.6 on the charger side.

CPO needs to review the charger specific implementation and configuration, as other settings out of standardized scope may apply.

Meter Values Reporting

Configure session meter values report interval on the charger, so the session’s progress will show up. We advise using a 15 seconds interval. You can usually configure this on the charger’s own dashboard, or use EV Charge dashboard, which can do it by OCPP.

To access this section in EV Charge, from the Menu, click Stations. A paginated list of all stations is shown in a tabular format. Click Actions for the specific station. On the station’s page, click Configuration on the top right corner to access Configuration page, the click Custom tab.

Example of Setting Interval

Figure: OCPP 1.6 example of setting the interval in the Station’s Configuration form on Tridens EV Charge dashboard.

To show active power measurement in mobile app, CPO needs to configure the charger to send the certain measurements in scope of the charging session (usually at least kW for power and kWh for energy). Once again, this is usually doable by the charger’s dashboard or EV Charge dashboard, where OCPP’s MeterValuesSampledData setting can be used.

To navigate to this area in EV Charge, go to the Menu and select Stations. You’ll see a paginated list of all stations in a tabular format. Click on Actions for the specific station. Once on the station’s page, access the Configuration page by clicking on Configuration at the top right corner, then navigate to the Custom tab.

Example of Setting Measurands

Figure: OCPP 1.6 example of setting measurands in the Station’s Configuration form on Tridens EV Charge dashboard.

Important measurands to cope with:

NameDescriptionOCPP 1.6 NameOCPP 2.0.1 Name
Energy ImportInstantaneous imported energy (Wh or kWh) to the vehicle.Energy.Active.Import.IntervalEnergy.Active.Import.Interval
Power ImportInstantaneous power (W or kW) import to the EV.Power.Active.ImportPower.Active.Import
Current ImportInstantaneous current (A) import to the EV.Current.ImportCurrent.Import
VoltageInstantaneous voltage (V) supply between grid and EV.VoltageVoltage
Battery State of ChargePercentage representing the vehicle’s battery state of charge.SoCSoC

Table: List of measurands settings in OCPP 1.6 and 2.0.1.

System is using the following energy consumption detection for a session, as there are different varieties of reporting by chargers:

  • Chargers reporting an absolute energy meter values at session start, intermediate, stop. Energy of all the sessions on the charger so far.

  • Chargers reporting the session relative energy meter values at session start, intermediate, stop. Energy of the latest session.

  • Chargers reporting an absolute energy meter value at the start and stop of session, but in the intermediate time, they are sending relative session values.

Tridens EV Charge also checks the time of meter value reports and ignores the obsolete reports. Meter value report is obsolete when its reported time is older than the last successfully processed report’s time.

Meter values which are related to the specific charging session and representing measurands related to it.

Session Meter Values Interval

Interval in seconds, by which the charger will send the meter value reports to the central system during the charging session. Suggested interval is 10-15 seconds.

Refers to MeterValueSampleInterval of OCPP 1.6 and SampledDataTxUpdatedInterval of OCPP 2.0.1.

Session Meter Values Measurands

Measurands which the charger will send on ‘Session meter values interval’. Suggested: power, energy, state of charge, voltage, current.

Refers to MeterValuesSampledData of OCPP 1.6 and SampledDataTxUpdatedMeasurands of OCPP 2.0.1.

General Meter Values

General meter values are reported independent of the session and may be required in the scenarios of the sessions which are being terminated by the final parking.

General Meter Values Interval

Interval in seconds, by which the charger will send regular meter value reports to the central system during the charging session.

Refers to ClockAlignedDataInterval of OCPP 1.6 and AlignedDataInterval of OCPP 2.0.1.

General Meter Values Measurands

Measurands which the charger will send on ‘General meter values interval’. Suggested: power offered.

Refers to MeterValuesAlignedData of OCPP 1.6 and AlignedDataMeasurands of OCPP 2.0.1.

Session Event Retry

Retry to send the event in case of failure. Suggested value is 3.

Refers to TransactionMessageRetryInterval of OCPP 1.6.