Chargers
Understand charger objects and how Joulo represents your EV chargers
A charger in Joulo represents a physical EV charging station linked to your account. Joulo supports chargers from multiple manufacturers, all accessible through a unified API.
Charger object
{
"id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
"nickname": "Garage",
"connection_type": "easee",
"status": "online",
"mid_certified": true,
"is_charging": true,
"current_session": {
"id": "f0e1d2c3-b4a5-6789-0abc-def123456789",
"started_at": "2026-04-09T08:15:00Z",
"kwh_so_far": 12.45
},
"latest_meter_wh": 5432100,
"meter_updated_at": "2026-04-09T10:30:00Z"
}Fields
| Field | Type | Description |
|---|---|---|
id | string (UUID) | Unique identifier for the charger. |
nickname | string | User-defined name, set in the Joulo app. |
connection_type | string | How the charger connects: easee, wallbox, zaptec, enphase, ocpp, smappee, v2c, or other. |
status | string | Current connection status of the charger. |
mid_certified | boolean | Whether the charger has a MID-certified energy meter for official metering. |
is_charging | boolean | Whether the charger currently has an active charging session. |
current_session | object | Active session details. Only present when is_charging is true. |
latest_meter_wh | number | Latest OCPP meter reading in watt-hours. Present when meter data is available. |
meter_updated_at | string (ISO 8601) | Timestamp of the latest meter reading. |
Connection types
Offline behaviour
Connecting a charger to Joulo never makes charging depend on the internet. The CSMS is a read path for metering data, not a gatekeeper for authorization:
- On every
BootNotification(and periodically on reconnect) Joulo pushes an OCPP configuration that makes the charger autonomous:AuthorizationCacheEnabled=true,LocalPreAuthorize=true,LocalAuthorizeOffline=trueandAllowOfflineTxForUnknownId=true. - Chargers with a vendor-specific autostart key (for example Peblar / Prodrive
AuthorizeMode=Automaticwith a localAutoAuthorizeIdtoken) are configured to self-start on plug-in, so charging never waits for aRemoteStartTransactionfrom the CSMS. Authorizerequests that do reach the CSMS are accepted by default, unless you enabled the RFID whitelist for your charger in the dashboard.- Transactions started while the charger is offline are delivered when the WebSocket reconnects (standard OCPP 1.6 offline transaction queuing), so no session data is lost.
Configuration is pushed with a diff against the charger's own GetConfiguration answer, and the accepted values are stored per charger. The Joulo dashboard shows a "works without internet" confirmation on chargers that confirmed all four offline keys. Brands that don't expose these keys but support the OCPP Local Authorization List instead get their approved RFID tags pushed as a local list for the same offline resilience.
Already connected to another OCPP backoffice? If the charger is already configured to an existing OCPP backoffice (its installer, a CPO / charge-card provider, or an energy supplier), be careful when changing the settings. A charger usually connects to one backoffice at a time, so pointing it at Joulo disconnects that link and stops the services relying on it (public charging, expense reimbursement, monitoring). Confirm you're allowed to change it before you do.
You can register OCPP chargers programmatically using POST /chargers. The response includes the WebSocket endpoint and password to configure on your charge point:
{
"id": "b2c3d4e5-f6a7-8901-bcde-f12345678901",
"nickname": "Oprit",
"connection_type": "ocpp",
"status": "offline",
"ocpp": {
"identity": "CHARGER-001",
"endpoint": "wss://ocpp.joulo.nl/CHARGER-001",
"password": "a8f3b2e1c4d5"
}
}The OCPP password is only returned once when the charger is created. Store it securely.
Cloud-connected chargers (Easee, Wallbox, Zaptec, Enphase, Smappee, V2C) must be linked through the Joulo dashboard by signing in with your manufacturer account.
Enphase support is currently limited by Enphase API coverage and data granularity. Joulo syncs all data the API provides, but timing and session detail can differ from direct OCPP integrations.
MID certification
Chargers with mid_certified: true have a MID-certified (Measuring Instruments Directive) energy meter. This means the kWh readings are legally verifiable and can be used for official ERE-credit registration.