Offline Charging and Data Back-Fill: OCPP Reliability in the Real World
Basements, underground bike sheds and rural sites lose 4G signal. A charging station that simply stops when the network drops creates angry riders and lost revenue. OCPP hardware designed for operations handles offline periods deliberately.
Layer 1: Local Authorization
Wanlin sockets maintain a local authorization list (up to 500 cards, synchronized via Local Authorization List Management). When offline, whitelisted cards still start sessions; QR sessions use the platform's cached rules where applicable.
Layer 2: Session Continuation with Local Rules
Active sessions continue under the device's local strategy: last known TxProfile limits, per-socket maximums and all seven safety protections remain enforced. Charging does not stop because the network did.
Layer 3: Transaction Storage and Back-Fill
Session records, metering values and status changes are stored locally. On reconnection, the device back-fills the CSMS with the queued transaction data so billing, reporting and diagnostics stay complete — including StartTransaction/StopTransaction for sessions that began offline.
Layer 4: Time Integrity
Metering timestamps are device-side, so energy attribution survives temporary clock or connectivity issues; the station resynchronizes time with the platform after reconnect.
Conclusion: when comparing OCPP sockets, ask exactly what happens offline: can it still charge (yes), does it keep safety limits (yes), and does billing data survive (yes, with back-fill). WANLIN-002/010 are engineered to answer all three the way operators need.
