The specification sheet says 150 kW, but the car shows only 70 kW at the fast charger. This does not automatically indicate a fault. Manufacturers generally state the maximum possible charging power. It is reached only with a suitable state of charge, an appropriate battery temperature and a sufficiently powerful charger.
What matters for journey time is not the brief peak, but the average charging power over the entire charging stop.
Charging power is not constant
During DC charging, the battery management system continuously controls how much power the battery can safely accept. This produces a charging curve. At a low state of charge, the power may initially rise, reach its peak and then fall again. Above around 80% in particular, the vehicle significantly reduces the power to protect the cells.
A car with a high charging peak therefore does not necessarily charge faster throughout the entire session than a model with a lower peak but a more stable charging curve. For a meaningful comparison, charging times from around 10% to 80% are more informative than a single kW figure.
The most common causes at a glance
| Cause | Typical behavior | What helps? |
|---|---|---|
| High state of charge | Power gradually falls from around 60% to 80% | On long trips, charge earlier and, if appropriate, end the stop before reaching 80% |
| Cold battery | Significantly lower power, especially shortly after setting off | Select the charger as the destination in the navigation system and use preconditioning |
| Very warm battery | Power is limited after high-speed driving or several charging stops | Allow the vehicle and battery to cool down if the thermal management system is insufficient |
| Charger limitations | Power remains below the vehicle’s maximum | Check the charger’s power rating or try a different charging point |
| Shared power | Charging speed falls when an adjacent connector is used | If possible, choose an available charging point that does not share power |
| Technical limitation | Unusually low figures repeatedly occur under favorable conditions | Have the software version, error messages and vehicle diagnostics checked |
Battery temperature and preconditioning
Lithium-ion cells charge fastest within a suitable temperature range. In winter, the battery is often still too cold after only a few miles or kilometers. The vehicle then limits the charging current. A warm cabin does not automatically mean that the battery is warm enough as well.
Many EVs can bring the battery to the right temperature before a fast-charging stop. This function often starts only when a compatible fast charger is selected through the built-in navigation system. Depending on the model, manually entering it as a regular address may not be sufficient. Cold battery → reduced charging power, even if the charger could deliver considerably more.
The charger can also limit power
The power stated for a charging station is also a maximum. It may be reduced by the station’s technical design, the available grid capacity or power sharing between several connectors. Voltage and current also interact: despite a suitable advertised kW rating, a vehicle may remain below its maximum at a particular charger if the charger cannot provide enough current at the battery’s voltage.
If the charging speed is unusually low, it is worth checking the charger display and charging app. If the station reports reduced power, the cause is probably not the car. Testing another fast-charging station usually provides more clarity than trying the same connector repeatedly.
AC charging has different limitations
When charging with alternating current, the car’s onboard charger determines the upper limit. For example, a home wall charger may be able to supply more power than the vehicle can accept. Single-phase charging, an incorrectly configured wall charger, building load management or an unsuitable cable may impose additional limits.
The amount of energy displayed in the vehicle may also be lower than the energy drawn from the grid. Charging electronics, battery temperature control and control units cause losses. Although this does not always affect the displayed kW figure, it extends the charging session and increases grid consumption.
How to identify the cause systematically
- Check the vehicle’s limit: Distinguish between its maximum AC and DC charging power.
- Note the state of charge: If possible, test fast charging with a low state of charge rather than an almost full battery.
- Prepare the battery: Start navigating to the charger in good time and activate preconditioning if available.
- Check the station: Verify its power rating, any connector power sharing and error messages.
- Make a comparison: Charge under similar conditions at another suitable station.
If the charging power repeatedly remains far below the usual figures for the model despite a low state of charge, a battery at the right temperature and a functioning station, a service center should check the fault memory, thermal management system and condition of the high-voltage battery. Individual slow charging sessions, however, can usually be explained by the conditions at the time.
