How to calculate the charging time of your electric car

If you own an electric vehicle, you’ve probably wondered how long it will take to recharge your battery. The time it takes to recharge an electric car can vary depending on several factors. In this article, we’ll explain how to calculate your electric car’s recharge time and give you tips on how to optimize that time.

Your vehicle’s battery stores direct current (DC) energy, but the electrical grid provides alternating current (AC) energy. Your vehicle can convert AC power to DC, to recharge its battery, with its built-in charger. When you use a household plug adaptor, or a “Type 2” cable (either or both of which are often supplied with your vehicle), it puts a strain on your built-in charger. However, this charger is an expensive component and is often limited to 7kW (single phase) or 11kW or even 22kW (three phase). It is thus intended for auxiliary recharges or of long duration (at home the night or at destination).

To recharge more quickly (during a break or during a leisure activity), we use charging stations that integrate more powerful chargers, in order to recharge more quickly, with more power. In this case, the charging station can use a dedicated cable that charges your battery directly without going through the vehicle’s built-in converter.

The choice of the charging station

Not all fast charging stations are created equal. Power is expressed in “kW”: the higher the number, the faster the station can theoretically charge your vehicle. But this depends on several factors that we will explain here, in order to better estimate the time and cost of charging.

The capacity of the battery

Battery capacity is one of the most important factors in determining the recharge time of an electric car. The higher the capacity, the longer the recharge time. To get an idea of how much energy is delivered in an hour, you can take into account the power of the charging station.

For example, if you connect your vehicle to a 25kW charging station, in one hour your battery can store up to 25kWh. However, this calculation must be qualified by the choice of cable or the level of charge of the battery which can reduce the power.

Tolerated load power

Every electric car has a maximum allowable charging power. This means that even if you plug into a charging station that delivers more power, your car won’t be able to take advantage of it if it’s not designed for it. To find out the maximum charging power tolerated by your vehicle, refer to its documentation. Please note that the maximum charging power is most often only reached when the battery is at a low level of charge.

The cable used

The type of cable used will often influence the charging time. If you are using a charging station where you plug in your own cable, it is the charger built into your vehicle that may limit power and increase charging time. Fast charging stations have their own built-in chargers, which are more powerful, and can reduce charging time. However, your vehicle must be able to tolerate this power.

When you use your own cable, your vehicle and its built-in charger can impose its own limits. Thus, if your vehicle is only equipped with a single-phase charger, the recharge will not exceed 7kW even if a three-phase charger can reach 22kW on this same terminal. To avoid these limits, choose an attached cable (CCS or CHAdeMO, depending on the vehicle).

The battery level

Le niveau de charge de la batterie peut également influencer le temps de recharge. En règle générale, la batterie charge plus rapidement lorsque son niveau se trouve dans la plage de 20% à 80%. Cependant, au-delà de 80% de chargement, la puissance de charge a tendance à se réduire progressivement. Ainsi, vous optimiserez vos temps de recharge (et la durée de vie de votre batterie) si vous limitez vos recharges au quotidien à 80%.

Sur un long trajet, pensez à recharger à 100% juste avant le départ, puis recharger à 80% à chaque pause ; il est alors plus efficace (moins de temps perdu) de repartir et continuer jusqu’à la suivante, ou jusqu’à votre destination.

The climatic conditions

Temperature extremes can also affect the charging speed of your electric vehicle. Batteries like moderate temperatures, ideally between 20°C and 25°C. In periods of extreme cold or heat, it will be necessary to plan a longer recharging time.

Your consumption can be reduced by a headwind, by rain, by the use of heating or air conditioning (although these devices are less energy consuming than we imagine). Cold air is harder to “break through” because it is heavier (aerodynamic vehicles do better), and even your tires can increase your energy consumption outside the expected season. Note also that these observations are also largely true for a combustion vehicle, but you will be more careful with an electric vehicle.

By following these tips, you can reduce the time it takes to recharge your electric car. We invite you to use the Stations-e network of charging stations to recharge your electric car. With this information, you can now better understand the charging time of your electric car and optimize this step of your journey.

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