What happens
The car charged, but on the platform the session shows 0 kWh, no meter values during charging, or it never closes or bills at all.
Check it in two minutes
Run a short session with the charger on the test server: it tells you whether meter values carry the energy register, how often they arrive and whether the charger closes in the right order. Those are exactly the three warnings we've seen most. Open the OCPP test server →
The causes, most likely first
1. The charger says “available” before closing the session
A charger we tested sent StatusNotification Available one second before StopTransaction. A platform that treats the session as lost when the connector frees up no longer waits for the closing message, which is the one carrying the energy. That's how 3 of 4 sessions in its test were lost.
How to fix it: Ask the manufacturer for the right order (close first, then status). askacharge.com completes the session if the closing message arrives late.
2. Meter values lack the energy register
OCPP lets you choose what is measured (MeterValuesSampledData). If the charger only sends power or current and not Energy.Active.Import.Register, the platform has no kWh until the end.
How to fix it: Add Energy.Active.Import.Register to MeterValuesSampledData.
3. It sends meter values every 15 minutes
A charger we tested shipped with MeterValueSampleInterval=900: a ten-minute session showed no energy until it ended.
How to fix it: Set it to 60 seconds. askacharge.com does it automatically on connect when it's 0 or above 300.
4. The meter resets
Some chargers start every session at 0 instead of sending the cumulative register, or lose it after a restart. Energy comes out negative or absurd.
How to fix it: Check that meterStart and meterStop are the meter's cumulative register, in Wh.
What askacharge.com does
Each session's energy is split by the meter readings, and if the closing message arrives after the “available” notice (within 24 h and from the same charger), the session is completed with its energy instead of being left orphaned.
Frequently asked questions
Why doesn't my OCPP charger send kWh while charging?
Usually because MeterValuesSampledData doesn't include Energy.Active.Import.Register, or because MeterValueSampleInterval is too high (900 s) or set to 0.
What is Energy.Active.Import.Register?
The cumulative reading of delivered energy, in Wh. It's the measurement a platform needs to bill per kWh.