Audi e-tron charges on DC but not on AC

You can rapid-charge fine at a motorway station. You can rely on the car for long trips. But the home wallbox, or any AC point, refuses to start a session, or starts and quickly cuts out. That is a particularly frustrating split: the car works, just not in the place where you charge it 90% of the time.

The reason the split exists is that AC and DC charging take very different paths through the car, and a fault in just one of those paths can leave the other completely unaffected.

Why AC and DC behave so differently

• DC charging sends DC straight to the battery via the two large pins at the bottom of the CCS Combo 2 inlet. The on-board charger (OBC) is barely involved.
• AC charging comes in through the upper Type 2 pins, is negotiated by the OBC, converted to DC inside the car, and only then sent to the battery.

If DC works and AC does not, that almost always means the OBC or the AC handshake is the issue, not the battery or the inverter. The good news is that the most common causes are external to the car.

What to check, in order

1. Try a different AC charger. A public 22 kW station, a friend's wallbox, anything that is not your usual unit. If AC works there, the original wallbox is the cause (often earthing/PE, RCD configuration, or a faulty contactor).
2. Swap the cable. A worn or non-compliant portable Type 2 cable is by far the most common cause of "AC just stops." An Audi e-tron compatible Voldt® charging cable takes the cable out of the diagnosis in a single swap.
3. Look at temperature. Below about 4°C, AC charging can derate or refuse to start if the battery is very cold and very low. Drive a few kilometres to warm the pack, then retry.
4. Avoid deep discharges. A battery sitting at 0% in cold weather is the worst-case scenario for AC start-up. Try not to leave the car in that state.
5. Read the error code. If the car shows an error in the MMI or in the My Audi app, write it down. The exact code is what an Audi technician needs to map the fault to the right control unit.

The technical detail

The original e-tron 55 and the e-tron 50 accept up to 11 kW AC three-phase via the OBC, and up to 150 kW DC (50) or 150–155 kW DC (55) on a CCS station. The Q8 e-tron facelift pushes DC up to 170 kW. The OBC is a single failure point for everything AC: if it has a fault on one phase, the car will either drop to single-phase at a lower rate, or refuse the session altogether, while DC continues to work normally.

Bottom line

Rule out the cable and the wallbox first. If AC still fails on a known-good cable and a known-good charger while DC works, that points at the on-board charger, and that is a dealer job.