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Why does my ev charger only load on one phase?

Updated

Why is my wallbox only charging on one phase?

If your wallbox is only charging on one phase, there can be several causes. Work through the following points step by step – from the simplest to the most complex.

1. App settings

Check phase configuration Is the wallbox set to 3 phases in the app? An incorrect base configuration will result in single-phase charging only.

Automatic phase switching & PV surplus Is the wallbox set to automatic phase switching? Three-phase charging requires at least approx. 4.1 kW of PV surplus. If less surplus is available, the system automatically switches to single-phase (from approx. 1.4 kW) to prevent the charging session from being interrupted. → Check the current PV surplus in the app.

Manual mode active? Check whether a manual charging mode with a fixed single-phase setting has accidentally been activated.

2. Charging cable check

Cable type Type 2 charging cables come in single-phase and three-phase versions. On a single-phase cable, the lower pins in the plug are "empty". Check the labelling or the data sheet:

  • "3.7 kW" or "7.4 kW single-phase" → single-phase cable
  • "11 kW" or "22 kW" → three-phase cable (required for 3-phase charging)

Extension or adapter cables If a three-phase charging cable is combined with a single-phase extension, the vehicle will only charge single-phase. Remove all adapters and extensions and test again.

Defective cable Loose contacts, damaged wires or oxidised pins can interrupt individual phases. As a test, connect another cable that is confirmed to be three-phase. If the wallbox then charges three-phase → the cable is defective.

3. Vehicle-side causes

Plug-in hybrids (PHEV) Plug-in hybrids can generally only charge single-phase, most of them with a maximum of 3.7 kW. This is not a fault, but a hardware characteristic of the vehicle. Examples: Opel Astra PHEV, Kia Niro PHEV, Mitsubishi Outlander PHEV, many BMW, Mercedes and VW hybrids.

Single-phase onboard charger (OBC) in EVs Some fully electric vehicles also have a single-phase OBC, e.g. Opel Corsa-e or Mazda MX-30. In this case, the vehicle will only charge on one phase by design – regardless of wallbox and cable. Check the OBC specification in the vehicle manual or data sheet.

4. Home installation & fuses

Check circuit breakers (MCBs) Are all three phase breakers for the wallbox switched on in the distribution board? A tripped breaker on one phase will result in only 1–2 phases delivering power.

Residual current device (RCD) Is the RCD of the wallbox switched on and not tripped?

Connection at the wallbox Some wallboxes are deliberately wired for single-phase operation only. Typical case with self-installation: only L1, N, PE have been connected. → This can only be verified by a visual inspection inside the opened device by a qualified electrician.

Grid type / house connection A three-phase wallbox requires a 400 V three-phase connection. On a pure 230 V connection, three-phase charging is physically not possible.

5. Wallbox configuration

Internal phase configuration Check the configuration menu of the wallbox (web interface, manufacturer app, DIP switches): Is the wallbox internally configured for three-phase operation? Some models have a switch or parameter that toggles between 1- and 3-phase operation.

Firmware up to date? Outdated firmware can cause faulty phase switching. Check the software version, install updates, and reset the wallbox if necessary.

6. Hardware defect of the wallbox

If all of the above points have been ruled out, the wallbox may be defective (e.g. a faulty phase contactor). In this case:

  • Contact your installer to measure the voltage on each phase (qualified electrician only, working with the system de-energised).
  • Contact the wallbox manufacturer (log files / diagnostics / replacement).