Electric car charging curve: complete guide to times, power, and battery

Electric mobility is no longer a future promise: it is the present. However, anyone who drives an electric vehicle (or is thinking about purchasing one) soon finds themselves dealing with a concept as technical as it is crucial: the charging curve.
Understanding how it works, what factors influence it, and how to make the most of it can make the difference between a quick stop and an endless wait.

This comprehensive guide will analyze in detail what the charging curve is, how it behaves under different conditions, what the most common myths are, and how future technologies are already changing the rules of the game.

What is the charging curve of an electric car and how is it measured

Technical definition and references to charging power

The charging curve represents the trend of power transferred to the battery of an electric vehicle during the entire charging process. It is therefore not a constant line, but rather a graph that shows even significant variations based on the state of charge (State of Charge – SoC), the vehicle technology, and operational conditions.

Explanation in simple words

If we wanted to simplify, we could compare it to filling a glass: at first, the water is poured quickly, then it slows down to avoid spilling. Similarly, the battery receives a lot of power at the beginning, but as it approaches full, the speed decreases.

Why it is a key concept

Knowing how your car behaves during charging helps plan trips better, avoid downtime, and even extend the battery life. It’s not just a technical detail: it's a practical tool for managing an electric vehicle effectively.

How the charging curve works during the EV charging process

The three phases of battery charging

1. Initial phase – Rapid charging at maximum power
   Here the battery accepts the maximum power that the charging station (and the vehicle) can supply. This is the fastest and most efficient phase in terms of time.

2. Intermediate phase – Stabilized power
   The charging speed remains high, but a slight decrease begins as the battery approaches a certain charge level.

3. Final phase – Reduction for battery protection
   Once a threshold is exceeded (usually between 80% and 90% of SoC), the power drops drastically to avoid overheating and stress on the cells.

Differences between direct current (DC) and alternating current (AC)

• DC Fast Charging: the initial power is very high (up to hundreds of kW) but decreases more quickly. Ideal for short charging during travel.

• AC Charging: the power is lower and constant, often limited by the vehicle's onboard charger, with less "drastic" curves.

The role of the Battery Management System

The BMS is the brain that manages the charging, monitoring temperature, voltage, and current. It decides when to reduce power to preserve the health of the battery.

Factors that influence charging speed and the shape of the charging curve

Maximum power of the charging station or wallbox

The power delivered cannot exceed the limit of the charging point. An ultra-fast station at 350 kW will be useless if the vehicle accepts a maximum of 120 kW.

Battery capacity and cell technology

• NMC: excellent performance in fast charging, but with sharper drops in the final phase.

• LFP: more thermally stable, with less pronounced curves but lower peak powers.

Initial state of charge

Charging from 10% to 80% is generally faster than continuing to 100%. After that threshold, the curve inevitably becomes flatter.

External temperature and weather conditions

• Cold: slows down the chemical reaction, reducing the maximum power accepted.

• Heat: can cause overheating and thermal protection interventions.
  
  
  

Software limitations

Many manufacturers impose power limits to protect the battery, sometimes adjustable via OTA updates.

Real examples of charging curves for popular models

Comparison between models

• Tesla Model 3: high peaks and maintenance of power up to 50% SoC.

• Volkswagen ID.3: lower maximum power but a more regular curve.

• Hyundai Kona Electric: optimized for AC charging, with effective thermal management.
  
  
  

How to read a charging graph

On the horizontal axis, we find time or SoC, and on the vertical one, the power (in kW). The point of maximum efficiency is usually found between 10% and 60–70% charge.

Difference between 10–80% and 80–100%

Going from 80% to 100% can take almost the same time as the 10–80% stretch, often making it less convenient to aim for a "full" charge while traveling.

How to reduce charging times and improve efficiency

Plan stops

Knowing your vehicle's curve allows you to stop only when the charging speed is optimal, avoiding unnecessary waits.

Utilize the optimal battery level

Starting the charge with a low SoC (but not critical) and stopping at 80% maximizes the average speed.

Use of apps and tools

• Official apps from car manufacturers to monitor power in real time.

• Third-party apps like ABRP or EVNotify for detailed analysis and charging planning.

Battery preconditioning

Heating the battery in winter or cooling it in summer before fast charging can significantly reduce times.

Innovations and future trends

Ultra-fast charging stations

New infrastructures promise power up to 600 kW, capable of charging in a few minutes, provided the batteries support it.

Solid-state batteries

They offer "flatter" curves, reducing power drop in the final phase.

Artificial intelligence

Predictive algorithms will adjust power based on climate, destination, and vehicle conditions, optimizing charging times and battery life.

Frequently asked questions (FAQ)

What is the charging curve?

It is the graph that shows how the charging power of the battery varies over time.

Why does charging slow down after 80%?

To protect the cells and prevent overheating.

Is the curve the same for all charging stations?

No, it depends on both the vehicle and the power of the charging station.

How to monitor it?

With dedicated apps or diagnostic tools connected to the vehicle.

Can it be kept constant?

Not at the moment, but new technologies are approaching this goal.

The charging curve is not a concept for professionals but a practical tool for every electric driver. Knowing it means optimizing trips, reducing stop times, and preserving the battery.
With upcoming innovations, charging will soon be even faster, more efficient, and more predictable.