OCPP and OCPI are frequently discussed as alternatives and they are not. OCPP is how a charger talks to its own backend. OCPI is how that backend talks to other operators' backends so a driver from one network can charge on another.
Confusing the two produces requirements documents asking chargers to support OCPI, which is not where it lives.
The two roles in roaming
A charge point operator owns physical infrastructure. A mobility service provider owns the driver relationship, issuing the card or app. Roaming is the arrangement that lets a provider's driver use an operator's charger and the money find its way back.
One organisation can be both, which is common, and the roles remain distinct even when they sit in the same company.
What roaming interfaces actually exchange
- Location and connector data, so drivers can find and filter chargers.
- Real-time availability, so an app can show whether a bay is free.
- Authorisation, so an operator can confirm a driver from another network may charge.
- Session and charge detail records, so the session can be billed between parties.
- Tariff information, so the driver can be shown a price before starting.
Data quality becomes an external problem
Once locations are published to roaming partners, errors in them are visible to drivers who have no relationship with you. A wrong coordinate, a connector type that does not match reality, or an availability feed that lags produces a driver who arrives and cannot charge.
Internally that is a data quality issue. Externally it is a review, and it affects the partner as much as you.
Availability accuracy is the hard part
Publishing that a connector is available commits you to it being usable. The gap between what a charger reports and what a driver experiences, which exists in every network, becomes commercially visible once it is exposed to roaming partners.
Networks that have not solved session success before joining roaming tend to discover the gap through partner complaints.
Settlement is not instantaneous
Charge detail records flow between parties on their own schedule, disputes happen, and reconciliation is a finance process rather than a technical one. A network joining roaming acquires an accounts function it may not have had.
The volume is small at first and grows with roaming traffic, which is precisely when it becomes difficult to do manually.
Direct connections versus a hub
You can connect to each partner individually, or through a roaming hub that aggregates many. Direct gives better commercial terms and more integrations to maintain. A hub gives reach with less engineering and a party taking a margin.
Most networks start with a hub and add direct connections to significant partners later, which is a reasonable sequence.
What to establish before committing
- Whether your platform supports the interfaces the partner requires, at the versions they run.
- Whether your location and availability data is accurate enough to publish.
- Who reconciles charge detail records and handles disputes.
- What tariff information you are obliged to publish and how quickly changes propagate.
- What happens commercially when a roaming session fails.