Introduction
Many EV owners have experienced this situation: you park next to another electric vehicle at a public charging station, plug into the same type of charger, and start charging around the same time—yet the car beside you seems to charge much faster. While their charging power climbs quickly, yours appears to increase slowly or level off early.
This often leads to frustration and questions. Is the charging station unstable? Is the charger favoring another vehicle? Or is there something wrong with your car? In reality, in most cases, this difference in charging speed is completely normal. It is the result of how electric vehicles are designed to charge safely and efficiently under different conditions.

The Vehicle, Not the Charger, Sets the Real Charging Limit
A common misunderstanding is that charging speed is determined mainly by the charging station. In practice, the charging station only supplies available power—the vehicle itself decides how much of that power it can accept.
Every EV is designed with a specific charging capability based on its battery chemistry, battery pack design, voltage platform, and onboard electrical systems. These limits are set deliberately to balance charging speed, safety, and long-term battery durability.

Once connected to a charger, the vehicle continuously monitors key parameters such as battery voltage, current stability, temperature, insulation status, and overall system health. This is not a one-time check at plug-in, but an ongoing process throughout the entire charging session. If any condition moves outside the ideal range, the vehicle will automatically reduce charging power—even if the charger itself can deliver more.

This is why two different EV models at the same charger can behave very differently. One vehicle may quickly ramp up to a high charging power, while another maintains a more conservative level from the beginning. This difference does not indicate a better or worse vehicle; it simply reflects different design choices and safety strategies made by manufacturers.

Battery State of Charge: The Biggest Factor Most Drivers Overlook
Among all factors affecting charging speed, the battery’s current state of charge is often the most important—and the most misunderstood. Many drivers notice that charging starts fast but slows down significantly as the session continues. This is not a problem with the charger; it is an intentional charging strategy built into every modern EV.

At low battery levels, the battery can safely accept higher power, allowing the vehicle to replenish energy quickly. As the battery fills up, internal resistance increases, and continuing to charge at high power would generate excess heat and accelerate battery aging. To prevent this, the vehicle gradually reduces charging power as the battery level rises.

This explains why two vehicles at the same charging station may charge at very different speeds even if they are the same model. If one vehicle arrives with a low battery and the other is already near mid-charge or higher, their charging behavior will look completely different. In other words, charging speed is not fixed—it changes continuously depending on how full the battery already is.

Temperature Matters More Than Most Drivers Realize
Battery temperature has a major impact on charging performance, especially in very cold or very hot conditions. Batteries do not respond well to high-power charging when they are outside their optimal temperature range, so EVs actively manage charging speed to protect the battery.

In cold weather, part of the incoming energy may be used to warm the battery before full charging power is allowed. During this period, charging can appear slow, even though the system is working exactly as intended. In hot environments, the vehicle may limit charging power or extend charging time to prevent overheating and reduce stress on the battery.

These temperature-related adjustments happen automatically and often invisibly to the driver, but they have a direct effect on charging speed. When charging feels slow, it is often because the vehicle is prioritizing battery safety over speed.

Charging Station Load and Communication Also Play a Role
Charging infrastructure itself can also influence real-world charging speeds. When multiple vehicles are connected at the same time, some charging stations dynamically distribute available power among users, which can reduce the maximum power delivered to each vehicle.
In addition, stable communication between the vehicle and the charger is essential. If communication conditions are not ideal, the vehicle may intentionally lower charging power to ensure a safe and uninterrupted session.

Conclusion
Significant differences in charging speed at the same charging station are rarely caused by a single issue. Instead, they result from a combination of vehicle design, battery state of charge, temperature conditions, and charging station behavior. In most cases, slower charging does not indicate a fault—it is simply the system operating as designed.
Understanding these factors can help EV owners set realistic expectations, reduce unnecessary concern, and make better decisions about when and where to charge.