If you’re thinking about buying an electric vehicle, or you already own one, the EV charging curve has probably raised a few questions. It can sound quite technical. But in reality, understanding it can help you charge your vehicle more efficiently, save time… and even save money.
Today, we’ll explain exactly what an electric car charging curve is, how it works, and why not all EVs charge in the same way. We’ll also walk you through the factors that influence charging power -the ones that often make you glance anxiously at the clock while waiting at a charging station.
What Is the Charging Curve of an Electric Vehicle?
Imagina que la carga de tu coche eléctrico es como llenar un vaso con agua. Al principio, el agua cae con fuerza y llena rápido. Pero, a medida que se acerca al borde, la cosa va más lenta, como si cada vez saliera menos.
Imagine charging your electric car is like filling a glass with water. At first, the water flows quickly and fills the glass fast. But as it gets closer to the rim, the flow slows down—almost as if less water is coming out.
That’s more or less how an EV charging curve works. It’s not linear. In other words, your car does not charge at the same speed from minute one all the way to 100%. Instead, charging speed varies depending on your battery’s state of charge.
In more technical terms, the charging curve is the graphical representation of the power at which the battery is recharged as a function of time and state of charge (SOC). Understanding it is essential if you want to get the most out of your electric vehicle and avoid unnecessary waiting times.
How Does the Charging Curve Work?
Let’s look at a practical example.
Imagine you own an electric vehicle that supports a maximum charging power of 100 kW. You plug it into a fast charger and see that at first it’s charging at full speed, close to 100 kW. However, once the battery passes 50%, that charging power starts to drop.
This is completely normal. In fact, it’s designed that way.
- Initial ramp-up (up to 20%). The battery prepares to receive energy, and charging power increases progressively until it reaches its peak.
- Optimal zone (20% to 60%). This is the most efficient section. The car charges at the maximum power allowed by both the vehicle and the charger.
- Tapering phase (from 70% or 80%). As the battery approaches full capacity, charging power is gradually reduced to prevent overheating and protect battery health.
- Final stretch (90% to 100%). Charging power drops dramatically. Charging from 90% to 100% can take as long as going from 20% to 80%. That’s why many drivers typically charge only up to 80% for daily use unless they need the extra range for a long trip.
Do All Electric Vehicles Have the Same Charging Curve?
No, charging curves vary from one electric vehicle to another. One of the main factors is battery architecture and how it’s designed to manage energy flow.
Some vehicles, such as certain models from Tesla or Hyundai, maintain high charging power for longer periods. Others start tapering earlier. This is why sometimes a car with a smaller battery can charge faster than one with a larger battery: the charging curve makes the difference.
In addition, the vehicle’s onboard charging system and its communication protocol with the charging station also play a role. So it’s not enough to look at battery capacity in kWh, you need to dig a little deeper.
Factors That Affect Charging Power
Battery Percentage
The fuller the battery, the slower the charging speed. This basic principle applies almost universally. The fastest charging speeds occur when the battery is below 50–60%. So on long trips, it may be more efficient to make more frequent but shorter stops instead of waiting for a single full charge to 100%.
Vehicle Connector and Charging Station
Charging speed also depends on the type of connector your vehicle uses and the charging station you plug into.
Fast DC chargers (such as CCS or CHAdeMO) allow high-power charging – but only if the vehicle is compatible.
For example, a car that only supports AC charging at 11 kW will not benefit from a 50 kW charger. Conversely, if your car supports 150 kW but you plug it into a 22 kW charger, your charging curve won’t look very impressive either.
Battery Degradation
Over time, batteries degrade, like any other component.
This affects both total capacity and charging performance. A degraded battery may reach safety thresholds earlier, causing charging power to taper sooner.
In short, the more years and charging cycles a battery has experienced, the more sensitive the charging curve becomes, and the earlier power reduction begins.
Vehicle Limitations
Manufacturers set specific safety limits that determine how the charging curve behaves.
These limits are related to the vehicle’s electronics, cooling system capacity, and battery thermal management. That’s why two cars with the same battery capacity can charge at different speeds—one may simply have better cooling or a more advanced electrical system.
Temperature
Both battery temperature and ambient weather conditions play an important role.
A cold battery (for example, after a winter night) will not charge efficiently at first. It needs to warm up before it can accept high power levels. Some vehicles include battery preconditioning systems that heat the battery before arriving at a fast charger—especially if the charging stop is programmed into the navigation system.
On the other hand, extremely hot conditions can also limit charging power, as the system reduces output to prevent overheating.
How Can You Make the Most of the Charging Curve?
Here are some practical tips you can apply in your daily routine:
- Charge between 20% and 80% if you’re aiming for speed and efficiency.
- Avoid charging to 100% unless it’s necessary for your journey.
- Check your EV’s specifications to know its maximum charging power.
- On long trips, plan short stops at fast chargers instead of long full charges.
- Use battery preconditioning before arriving at a fast charger, if your car supports it.
- Avoid frequent consecutive fast charges, as they may accelerate battery wear over time.
Understanding the electric vehicle charging curve is key to optimizing your charging time, protecting battery health, and ultimately improving your overall EV experience.
While not all electric vehicles have the same charging curve, knowing how yours behaves will help you plan better trips, charge more efficiently, and get the most out of your investment.
