Reference

Every EV charging term, defined plainly.

From OCPP to ISO 15118 to sanctioned load. Written and reviewed by RIOD engineering, so the definitions match how the terms are actually used in the field.

A B C D E G H I M N O P R S T U V

AFIR

Alternative Fuels Infrastructure Regulation. EU regulation (from 2024) mandating public charging targets, ad-hoc payment (contactless card at 50kW+ stations) and price transparency across the EU.

Autocharge

A pre-standard authentication method that uses the EV's MAC address (present on any ISO 15118-capable vehicle) as an identity token. Simpler than PnC to deploy but not cryptographically secure. Common in fleets and closed networks.

BLE

Bluetooth Low Energy. Used in EV chargers to authenticate drivers over their phone (basement scenarios), to configure the charger locally, and as a fallback when no cellular or WiFi is available.

BootNotification

The first OCPP message a charger sends on connecting to the CSMS. Includes vendor, model, firmware version and returns the heartbeat interval the charger should use.

CMS

Charging Management System. The backend software that monitors, controls, authorizes and bills EV chargers over OCPP. Also called CSMS or CPMS depending on context.

Control Pilot (CP)

The signaling line between an EV and an EVSE defined by IEC 61851. A PWM signal on the CP wire tells the vehicle how much current it may draw; the vehicle's response on the same wire indicates its state (A through F).

CP State (A-F)

The IEC 61851 vehicle states signaled on the control pilot: A (not connected), B (connected, not ready), C (charging), D (charging with ventilation), E (short to PE), F (fault). Most AC charging cycles between states A, B and C.

CPMS

Charge Point Management System. Commonly used interchangeably with CMS and CSMS. Some vendors distinguish CPMS (charger-facing operations) from CSMS (broader network management).

CPO

Charge Point Operator. The entity that owns and operates a network of EV chargers. In roaming contexts, the CPO provides charging service that eMSP customers can access.

CSMS

Charging Station Management System. OCPP 2.0.1 terminology for what earlier versions called the Central System, the backend that manages a fleet of chargers.

DISCOM

Distribution Company. The Indian utility responsible for last-mile electricity distribution. Sanctioned load, ToD tariffs and connection categories all come from the local DISCOM.

Dual-Partition OTA

A firmware storage design where the charger holds two firmware slots. OTA writes the new image to the inactive slot, verifies its signature, then boots into it. Failed boot rolls back to the previous slot automatically.

Dynamic Load Management

Software that continuously reallocates available site power across active charging sessions, so total draw stays within the sanctioned demand while maximising throughput. Essential for depots and multi-charger sites.

Eichrecht

German metering-law framework requiring signed, tamper-evident billing data for public EV charging. Charger firmware must digitally sign meter values so drivers can independently verify the energy they paid for.

eMSP

E-Mobility Service Provider. The entity that maintains the driver relationship, issues the app, RFID or contract, and handles billing to the end customer. May or may not own chargers.

Gireve

A French-origin roaming hub competing with Hubject, widely used in Western Europe for CPO-eMSP interconnection.

Hubject

A major EU-based roaming hub connecting CPOs and eMSPs across networks via OCPI. Also operates the V2G root PKI for cross-network Plug and Charge.

Idle Fee

A charge applied to a driver whose vehicle occupies a bay after the session has completed. Encourages bay turnover at busy sites. Enforced via CMS tariff engine and often confirmed by vision monitoring.

IEC 61851

The international standard defining conductive EV charging: physical connector types, control pilot signaling, safety states (A-F), and interlocking. IEC 61851-1 is the general requirements; -21 and -22 cover EV-side and DC-side respectively.

ISO 15118

The vehicle-to-charger communication standard that enables Plug and Charge (automatic authentication) and, in 15118-20, bidirectional charging (V2G). Uses TLS-secured PLC (power-line communication) between EV and EVSE.

MeterValues

The OCPP message that reports energy, current, voltage, temperature and other measured values during a session. Sampling interval and precision are configured per network.

NEVI

National Electric Vehicle Infrastructure. The US federal program funding highway EV charging deployment, with requirements including 97% uptime, ad-hoc payment support and standardised reporting.

OCPI

Open Charge Point Interface. A protocol between charge point operators (CPOs) and e-mobility service providers (eMSPs) that enables roaming, a driver on one network being able to charge on another and be billed correctly. Current major version is 2.2.1.

OCPP

Open Charge Point Protocol. The industry-standard messaging protocol between an EV charger and its central management system, over WebSocket. Current major versions are 1.6J and 2.0.1.

OCPP 1.6J

The JSON-over-WebSocket variant of OCPP 1.6, the most widely deployed version in commercial networks today. Supports optional profiles including Smart Charging, Remote Trigger and Firmware Management.

OCPP 2.0.1

The successor to 1.6J, adding a formal device model, richer security profiles, ISO 15118 support and improved smart charging. Adoption is growing; many new networks specify 2.0.1 as the minimum.

OCPP Heartbeat

A periodic OCPP message a charger sends to keep the CSMS connection alive and time-synchronise. Missing heartbeats indicate connectivity loss, not necessarily a broken charger.

OTA

Over-The-Air. A firmware update delivered remotely to a charger without physical access. OCPP's Firmware Management profile is the standard channel; secure OTA requires signed images, dual-partition rollback and staged campaigns.

Plug and Charge (PnC)

An ISO 15118 flow where the EV and charger authenticate each other via X.509 certificates over TLS, so the driver plugs in and charges without any card, app or RFID. Requires PKI infrastructure both sides trust.

Proximity Pilot (PP)

A resistor-encoded signal on the charging cable that tells the EVSE the cable's maximum current rating. Prevents a 32A cable from carrying 63A.

RCD

Residual Current Device. A protective device that trips when it detects imbalance between line and neutral currents (i.e. current leaking to ground). EV chargers typically use Type A or Type B RCDs; Type B detects DC residuals as well.

Roaming

Cross-network charging: a driver whose contract is with one eMSP charging on a CPO's network they don't have direct account with. Enabled by OCPI, usually via hubs like Hubject or Gireve.

Sanctioned Load

The maximum kW a site is contractually allowed to draw from the DISCOM (in India). Exceeding it triggers penalty tariffs or supply disconnection. Depot charging plans are constrained by sanctioned load, not transformer capacity.

Self-Resettable RCD

An RCD design that automatically retests and resets after a trip, distinguishing transient faults from persistent ones. Reduces truck rolls for nuisance trips on unattended chargers. RIOD ships a self-resettable RCD hardware module.

Session Success Rate

The percentage of attempted charging sessions that successfully deliver energy. A better uptime metric than ping-status, because a charger can respond to pings while failing every session.

SLAC

Signal Level Attenuation Characterization. The pairing handshake in ISO 15118 that binds the EV to the correct EVSE via power-line signal attenuation. Prevents cross-talk in multi-outlet DC installations.

Smart Charging

OCPP profile that lets a CSMS send ChargingProfiles to chargers, defining maximum current or power over time. The basis for load management, tariff-aware charging and grid-services participation.

StartTransaction / StopTransaction

OCPP messages that bracket a charging session. StartTransaction opens the session with meter start reading and driver ID; StopTransaction closes with meter stop reading and reason.

StatusNotification

The OCPP message a charger sends when its connector state or fault code changes. Reading these correctly is the difference between real fault detection and treating error codes as opaque strings.

ToD Tariff

Time-of-Day tariff. Electricity pricing that varies by time slot, typically cheaper at night and expensive in evening peaks. Depot charging schedulers shift load into cheap windows to minimise cost.

Truck Roll

A field-service visit to a charger site. Truck rolls are the single biggest operating cost for public networks; predictive maintenance and remote diagnostics exist primarily to reduce them.

Type B RCD

An RCD that detects both AC and DC residual currents (down to 6mA DC per IEC 62955). Required or recommended for EV charging where the vehicle's onboard charger can leak DC to ground, which Type A RCDs miss.

UPI

Unified Payments Interface. India's instant bank-to-bank payment system. For EV charging, UPI is the dominant public payment method: scan QR, pay, charge. Autopay mandates support recurring subscriptions.

UPI Autopay

The RBI-regulated recurring-payment framework on UPI. Used for EV charging subscriptions (fleet driver plans, apartment resident plans) so monthly debits happen automatically within mandate limits.

V2G

Vehicle-to-Grid. Bidirectional charging where the EV exports energy back to the grid or the building. ISO 15118-20 defines the protocol; grid-code compliance and utility programs define whether it's economically useful.