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Performance and charging time: how to avoid unpleasant surprises?

Just as there are different types of fuel for internal combustion engines, electric vehicle charging stations deliver different levels of power. However, the power and charging time are not the same for all vehicles at the same charging station. Chargemap gives you an overview of what you need to know to avoid unpleasant surprises at the charging station.

A few basic skills



What is the difference between kW and kWh?

This confusion is common, but it is easy to fix. To simplify things to the extreme, let's take the bathtub comparison:

Educational Visualization - Bathtub Analogy to Explain the Difference Between kW and kWh
  • The flow rate of the tap water corresponds to the current power of the charging station in kW.
    –> example: A three-phase11 kW AC charging station.

  • The bathtub corresponds to the capacity of the battery in kWh. The amount of water that is fed into the bathtub corresponds to the amount of energy supplied to the electric vehicle in kWh.
    –> example: If I connect my vehicle to an 11 kW AC charging station for an hour, I have theoretically recovered 11 kWh.

In other words: kw measures the instantaneous power of the charging station, while kwh measures the energy consumed by the charging station or delivered to the vehicle.


What is the difference between AC and DC charging?

Alternating current (AC) charging

Alternating current is the current that flows through the electrical grid. The battery of an electric vehicle can only store electricity in the form of direct current (DC).

An AC/DC converter under the hood of the vehicle converts the alternating current into direct current before it is stored in the battery. This conversion in particular requires additional charging time. AC charging stations generally offer normal to accelerated charging (up to 22 kW), but can sometimes go up to 43 kW.

Direct current charging (DC)

DC charging stations offer fast to ultra-fast charging (up to 350 kW). Here, the charging station is directly equipped with a powerful AC/DC converter, so that a DC power supply is possible and the vehicle battery can be charged immediately.


Do you know the technical characteristics of your electric car?

Newly minted e-car drivers are opening up a new world: charging. It is essential to know the technical characteristics of your vehicle in order to master its charging. When buying from a car dealership, it is very rare that the driver is trained to handle these new topics. This often leads to incomprehension and frustration among new e-car fans.

There are at least 4 things you need to know to understand how to charge your electric vehicle:

1. The capacity of the battery

This is the amount of energy, expressed in kWh, that the battery can store and feed to the engine when charging. It varies between 15 and 200 kWh. It should be noted that the larger the capacity of the battery, the longer the charging time at a particular charging station.

2. The type of internal charger

It is important to know the characteristics of the internal charger (single-phase or three-phase) in the vehicle, as it determines the charging power tolerated by the vehicle at AC and DC.

For alternating current, the tolerated power generally varies between 3 and 22 kW. With direct current, it can reach up to 270 kW today.

To put it simply: With a charging station that emits more kW than the vehicle can handle, the charging speed is adapted to the vehicle and limited.

Let's take two theoretical examples:

  • Sarah drives a Tesla Model 3 and connects it to a three-phase 22 kw AC charging station. After an hour, she expects to have charged 22 kWh, but finds that it is only 11 kWh.

    Sarah's first thought is to blame the charging station, which states more power than it actually delivers. However, the problem here is not the infrastructure, but the vehicle. Sarah is unaware that the TM3 only accepts a maximum of 11 kW of alternating current (AC).

  • Paul drives a Renault Zoé R110 (latest version). He connects his e-car to the same charging station as Sarah and charges 22 kWh in one hour.

    Here, Paul's Zoé can absorb the maximum power from the charging station and charges faster, as its internal charger accepts 22 kW alternating current.

Easily determine the charging time required for your vehicle depending on the charging station with the Free recharge time simulator available on Automobile Propre (translated from French using Google Translate).

3. Charging cables adapted to the vehicle

If the cable used for charging (for charging stations over 22 kW, a cable must be attached to the column) is not suitable, the power can also be throttled. 

It is therefore important that you familiarize yourself with charging cables that connect to your electric car and the preferred charging type are adapted.

4. Temperature and battery level

Additional factors (these are the last ones, I promise!) 😅 affect the amount of energy emitted by a charging station at a time T. A battery management system (BMScommunicates with the charging station and adjusts the power according to the battery's state of charge and temperature.

As long as the optimal conditions are not met, the maximum power delivered by the charging station and tolerated by the vehicle will not be reached.

To note:

  • If the battery level is less than 10% before recharging, the charging power will be limited.
  • From an average of 80%, the time to reach 100% will take at least as long as from 20% to 80%. As a general rule, it is not advisable to charge your vehicle to 100%, except before a long journey.
  • The ideal battery temperature is between 20 and 25 degrees Celsius. For this reason, the charge will take longer on hot or cold days.

Summary

Before you buy an e-car, you should be informed about at least the following points:

  • the power tolerated by your electric car with AC and DC charging, expressed in kW,
  • the battery capacity, expressed in kWh,
  • additional factors that may affect charging, such as the temperature inside and outside the vehicle, the type of cable used, or the battery's state of charge.

Once you are familiar with the characteristics of your electric vehicle and the basics of charging, you can Choose the charging stations that best suit your vehicle. This allows you to optimize the loading time and avoid unpleasant surprises on the bill.


souce :Performance and charging time: how to avoid unpleasant surprises? (chargemap.com)

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