Why Your EV Never Hits Its Advertised Charging Speed: The Answer Is on the Charger
Volts, amps and the connector limit: a plain-language look at why an EV rated for 400+ kW charges slower at many European fast chargers, and what to read on an Alpitronic charger's label to know the power you can really expect.
New electric cars keep arriving with charging figures that look stunning on paper: 400, 450, even more than 480 kW. Then you plug into a fast charger labelled "300 kW" or "400 kW" and the screen shows far less. That is not necessarily a fault. In a video recorded right next to a charger for the Mașina Timpului YouTube channel, Andrei Petcu set out to explain the gap without heavy formulas. Here is the same explanation in writing, checked against the charger makers' official specifications.
Power is volts times amps
The core rule is simple: charging power in kilowatts equals the battery's voltage multiplied by the current flowing through the cable. If a car's battery sits at 700 V and the charger supplies 500 A, you get roughly 350 kW. To reach around 480–490 kW at that same voltage, you would need close to 700 A.
There is a catch many owners miss. An "800-volt platform" is a label, not a constant. Real battery voltage drops when the pack is low and rises as it fills. In the video, Andrei points to 800 V cars whose packs actually run at a little over 500 V. That matters a lot: at the same current limit, lower voltage means fewer kilowatts.
The connector and the charger cap the current
This is where the charger itself comes in. Every unit and every cable has a maximum current. The official data sheet for the alpitronic Hypercharger HYC300, a very common sight in Europe, lists an output range of 150 to 1000 V, up to 300 kW in total and a 500 A maximum with a liquid-cooled CCS2 cable. The newer HYC400 goes up to 600 A on its CCS2 connector.
In Andrei's experience, most fast chargers he finds on the road top out at 500 or 600 A. More powerful hardware already exists: for its HYC1000 system, alpitronic lists a single-connector CCS2 dispenser rated above 1000 A. Those sites are still rare, though, and what counts is the charger you actually stop at today.
There is a second ceiling: the charger's total power. The label filmed in the video read 150–1000 V and a 500 A maximum, but the unit was a 300 kW model. With a battery at 700 V, it cannot deliver the full 500 A without exceeding 300 kW, so it trims the current to about 430 A. Sometimes the grid connection at the site limits things further.
The Zeekr 7X and a 400 V Tesla
Zeekr's official 7X leaflet from October 2026 gives a peak DC rate of 420–450 kW depending on the version, but adds that reaching it requires compatible high-power chargers with improved cooling, which are expected to spread across Europe over time. In other words, the carmaker itself says the brochure number depends on the charger.
At the other end is a 400 V car such as Andrei's Tesla. If he arrives with a low battery at a 500 A charger and the pack sits at, say, 360 V, he cannot pull more than about 180 kW, even though the car is rated for 250 kW. On a Supercharger he has seen a 254 kW peak, which by his own calculation meant well over 600 A at the battery voltage at that moment. For its new V4 Supercharger, Tesla publishes up to 500 kW for passenger cars, 615 A continuous current and a voltage range up to 1000 V, so it is ready for 800 V cars too.
What it means for drivers
- Don't blame the car first. If you never see the advertised peak, the charger's or cable's current limit may be the reason, not your battery.
- Read the label on the side of the charger. It lists the voltage range and maximum current. Multiply the current by your battery's approximate voltage for a realistic estimate.
- Use the charger's session screen. Alpitronic units show session details, including live voltage and current.
- Arrive with a warm battery. Preconditioning and pack temperature still matter just as much; see our guide to the DC charging curve.
- Don't buy on peak power alone. When comparing cars, look at 10–80% times on typical chargers, not just a peak figure that needs infrastructure that is still rare.
