What happens
You want to limit a charger's power (load sharing, your electricity contract, a test) and send it a SetChargingProfile. It answers Rejected, or answers Accepted and keeps charging at the usual power.
Check it in two minutes
On the test server, “Read configuration” returns the keys that decide this: whether the charger has the SmartCharging profile, how many profiles it allows and in which unit it wants them. If it says 0 profiles or W only, you know why it rejects. Open the OCPP test server →
The causes, most likely first
1. Amps to a charger that only understands watts, or the reverse
A charging profile is in A or in W. DC chargers usually accept only watts, and many AC ones only amps. A DC charger we tested rejected every profile because the platform always sent them in A.
How to fix it: Read ChargingScheduleAllowedChargingRateUnit (1.6) or the equivalent variable in 2.0.1 and send the profile in that unit.
2. The firmware allows zero profiles
If MaxChargingProfilesInstalled is 0, or in 2.0.1 the charger answers TooManyElements with a maximum of 0, the firmware doesn't have charging management enabled. On the charger we tested, a firmware update fixed it.
How to fix it: Ask the manufacturer for a firmware with Smart Charging and check that SupportedFeatureProfiles includes it.
3. The purpose doesn't match what's happening
A TxProfile only applies to a transaction in progress, with its number; with no active session it's rejected. A ChargePointMaxProfile only goes to connector 0.
How to fix it: With no session running, use TxDefaultProfile (it applies to the next ones). To limit the whole unit, ChargePointMaxProfile on connector 0.
4. It accepts but doesn't limit: another profile wins
The profile with the highest stackLevel of the same purpose wins. If there was already one with a higher level, or yours starts in the future (or the charger's clock is off), the new one sits underneath.
How to fix it: Request GetCompositeSchedule to see which limit it's really applying, and clear the old ones with ClearChargingProfile.
5. The limit is below what the car accepts
Below about 6 A per phase, many cars stop charging instead of charging slowly. It looks like the profile doesn't work, when in fact charging has stopped.
How to fix it: Don't go below 6 A per phase (about 1.4 kW single-phase, 4.1 kW three-phase).
What askacharge.com does
The profile is sent in the unit you choose (A or W) and the panel accepts “10 kW” directly; if the charger rejects it, we show the reason it gives. There's also a per-location limit, to share power between several chargers without writing profiles by hand.
Frequently asked questions
Why does SetChargingProfile return Rejected?
The most common causes: the unit (A or W) isn't the one the charger accepts, the firmware doesn't have charging management enabled (0 profiles), or the purpose doesn't fit (a TxProfile with no session in progress).
What's the difference between TxProfile and TxDefaultProfile?
TxProfile applies to a specific transaction that's already running. TxDefaultProfile applies to transactions that start from now on.