The energy window

Before power flows, the car tells the charger what it wants and when it is leaving, and the charger answers. In ISO 15118-20 that happens in the schedule exchange, which comes in two forms, the Dynamic and the Scheduled control mode, and a session uses one. In the Dynamic mode the car states its needs and the charger answers with only optional extras: a departure time, state-of-charge limits and a price schedule. In the Scheduled mode the charger answers with schedules to choose from.

In the Dynamic mode the car must give a departure time and three energy requests, a minimum, a target and a maximum, and it may add two V2X energy requests, a minimum and a maximum, along with state-of-charge limits. The V2X pair exists only in Dynamic contexts: the schedule exchange, and the bidirectional charge loops in both DC and AC. The charger’s answer carries no power schedule. The chart draws the three requests as three levels, with the V2X pair as optional extra lines; that drawing is this page’s reading, not something the schemas say.

In the Scheduled mode the charger offers one to three schedule tuples. Each holds a required charging schedule and an optional discharging schedule, and a schedule is a list of up to 1024 entries, each a duration and a power value. The car’s departure time and energy requests are optional here, and the V2X energy requests do not exist. The table shows which fields belong to which mode, read from the same data the chart uses.

The values on the chart are an illustration, and the page says so wherever they appear. What the sources give is the field names, which mode has which field, and whether it is required or optional. They state no unit for an energy request, a power value, a duration or the departure time, so the axes are relative. They also do not say how the V2X requests relate to the other three, or how a charger should turn a request into power: the path and the schedules are there to show the idea, not a rule.