How long will it take to charge your EV? 5 Things…

How long should I allow to charge?

Every electric car will take a different time to charge. Why? There are many factors. We’ll take a look at the Key Takeaways, and then those 5 factors. If you want to skip down to the 5 factors that affect charge, here they are:

Here are the Key Takeaways:

State of Charge or SoC. It’s a rookie error to imagine you’ll always be charging your EV from zero to 100%. It’s rare to discharge your car to 0%. The SoC is expressed as a percentage and is the amount of charge left in the battery. For best RATE of charge aim to maintain an SoC between 20 and 80%. You may have heard that the rate of charge is slower when you charge a battery from 80 – 100%. This is only true of very fast charge speeds (at public fast DC chargers). It’s not really a problem with at-home or slower public AC chargers.

Battery Temperature does affect battery health. In practical terms, there is a sweet spot for your car’s battery (at about 70F or 21C) and it does not like to operate in extreme cold (below 20F) or in extreme heat (above 90F). Extreme cold can really impact charge speed and that’s why battery preconditioning (where you heat the battery to optimize the speed and rate of battery charge) is useful.

Power implications. If there are other cars charging at the same time (and other electrical loads, say at peak hours of use compared with off-peak times) time to charge may increase. Cabin A/C, heating, lights, and any other car accessories being operated at the time of charging will decrease SoC and impact charge speed.  Battery degradation, voltage and current limits (of both the charger and the car) also affect the time.

To maximize charge speed and battery health, always use chargers that are compatible with your EV model. Rather than draining your battery to almost empty before recharging, consider more frequent charging. Avoid a full discharge followed by high-speed DC charging to 100%. If AC charging, it’s considered healthy to charge to 100% but it is recommended to limit charging to 100% with DC high speed charging.

Plan well to take advantage of best charging opportunities that suit your activity. Try to take advantage of charging when the car is not being used (while you’re at work, shopping, or sleeping) so that your charge costs are minimized and you and your car’s downtime are optimized.

Factors affecting EV charging duration

The time to charge Electric Vehicles (EVs) is influenced by several variables that can be grouped into three categories: the car's battery capacity, the type of charging used (whether AC level 1 and 2, or DC level 3 fast charging), and the charging station's specifications. Take a look at the following table. It depicts some of the factors that impact EV charging speed and the time required to charge the vehicle's battery completely.

Combine the different variables and you’ll have different charge-time outcomes (with some being more favorable than others). For example, for similar battery condition, to change the level of charge from 1 to 3 will result in faster charging rate.

A recent study conducted by the Union of Concerned Scientists (UCS) showed that faster (higher-powered) charging stations speed up the charging process up to 83%. You can save time on your travels and, by extension, the wait times at charging stations is shorter.

1. State of Charge 

The amount of charge remaining in an electric vehicle’s battery, or SOC, has an impact on the charging speed. SOC is the measure of how much charge is left in the battery as a percentage of its total capacity.

Roughly speaking, the time to charge a battery from 0% to 80% is about the same that it takes to charge from 80% to 100%.

The practical side of that is this: If you are on a long trip that requires charging en route, charge to 80% and stop every 2 – 3 hours and top up to 80%. You will never discharge your battery to zero in that time and you’re probably needing to stop anyway. The top up from say 40 or 50% back to 80% will take much less time and you’ll be on your way again. You might make an extra charge stop, but it will save you time and optimize battery health. If you charge to 100% on an ultrafast charger from time to time, that’s not going to have a significant effect.

You’ll hear the often-repeated myth that you should not discharge to below 20%, but that’s untrue. Keeping 20% in reserve is just a recommendation and you can safely discharge to a lower amount. Your car will even have a buffer of a few percent

Just as you shouldn’t drive until the fuel light switches on in an ICE car, you won’t be driving to zero% in an EV.

The long and the short of it is this: EV batteries have a robust battery management system which ensures your battery operates within certain limits of voltage, temperature, charge and discharge limits.

The following table shows the relationship between SoC and the charging period:

Charging speed also depends on the type of charger used (Level 1, 2 or 3), the temperature of the battery, and the power in kW of the charger. It is important to note that highspeed DC charging above 80% to reach 100% should be avoided regularly as it can reduce the lifespan of the battery.

2. Battery temperature

To ensure safe charging at optimal charging speed, (which also prolongs battery lifespan),  batteries are best charged within an optimal temperature range. Your BMS (battery management system) helps monitor that and with an understanding of the issues, you can create the right conditions to optimize your driving and charging experience.

Battery temperature is one of the most dominant factors that can significantly affect charging speed. Ambient temperatures and operating temperatures are important. When the battery is cold, it resists charging, which results in a slower charging process. On the other hand, when the battery is overly hot, it can damage the battery cells and negatively impact the battery’s lifespan. Extreme ambient temperatures may not affect you much, but it is important to know the definition of “extreme” to determine how it might impact your EV use. Extreme is defined as temps below 20F or -6C and above 90F or 35C.

If the battery is cold due to cold weather or prolonged vehicle inactivity, it might take longer to warm up before charging. Similarly, if the battery is hot due to sustained very high speeds coupled with extreme acceleration (as you might do on a racetrack), it might take longer to cool down before charging. It’s wise to adjust your charging habits accordingly to optimize charging speed and battery lifespan.

As technology evolves, more electric vehicles are coming equipped with advanced temperature management systems that can help regulate the battery temperature during charging and discharge. Here’s how you can avoid slower charging and potential battery damage due to extreme temperature: where possible, avoid rapid charging in extreme temperatures, park in shaded areas if very hot, and (if you have to cool or heat the cabin) don’t use the air-conditioning while you’re charging.

3. Other loads while charging

When you charge your EV, “other loads” (in and outside of the car itself) do have an impact on charging speed as they may draw power away from the charging process. These include other appliances or devices, such as air conditioning or headlights. To optimize charging time, avoid using other devices or appliances while charging your car.

So too, using heavy load devices at home (such as washing machines, dishwashers, and electric ovens) draw a lot of power. If you want to charge your EV more quickly choose a time when “other loads” are minimized.

A friend of mine was charging his EV while using the air conditioning, and he noticed that the charging speed was significantly slower than usual because the air conditioning was drawing power away from the charging process. Small adjustments to your charge routine help you optimize charging time and avoid unnecessary delays.

4. Battery deterioration

Electric Vehicle Battery Health Degradation

The performance of an electric vehicle (EV) greatly depends on the battery life and its degradation rate over time. Battery degradation is when there is a (significant) reduced capacity of the EV battery and resultant reduction in range. You might notice that over time you need to charge more frequently to achieve the same range.  The battery can deteriorate in health due to various factors such as overcharging, high temperatures, and continuous use.

To avoid battery deterioration, EV owners should monitor their battery health regularly and keep it within the recommended range of charge. Overcharging the battery (especially with DC ultrafast charging) can significantly impact its lifespan and performance, leading to slower charging times and shorter driving ranges.

Manufacturers offer guidelines on charging and maintenance which are worth following. When you take care of your EV’s battery health you will enjoy the full benefits of driving an electric vehicle.

5. Voltage and current limits

You don’t just plug into a charger and expect optimum charge rate. You have to consider the source of power and its capacity affects EV charging speed. The charging station provides electricity at a certain speed, and that level is determined by the station’s voltage and current limits (which may be subject to variations due to local demands and grid conditions). Understanding the voltage and current limits is crucial in determining the charging time and optimizing the process. Here are the essential details for the voltage and current limits that you need to know, to ensure efficient charging:

While higher voltage and current limits will result in faster charging times highspeed DC charging can also generate excessive heat and lead to battery degradation. This is why repeated frequent DC charging (especially from 80 to 100%) at ultrafast speeds is not recommended. Not all cars are able to receive an ultrafast charge (defined as over 150kW), but that is changing as technology and the industry matures.

Here’s a practical example:

Given the same conditions for a particular EV, the same car might take…

• 24 hours or more, to fully recharge with Level 1
• 8 hours with Level 2
• 30 minutes with Level 3 DC fast-charging

You can see how a Level 1 charger will suit drivers who only drive short distances for errands and commutes, and a Level 2 charger at home would be perfect for overnight charging for most drivers.

Conclusion and further resources

When you have an understanding of the factors that affect your electric car’s charging speed you’ll better be able to determine how long a charging session may take in different circumstances. And so, you can plan accordingly, optimize your charging experience and efficiently power up your vehicle.

Factors that impact charging speed include:

• the type of charging equipment used
• the capacity of the EV’s battery
• the car’s own onboard inverter and BMS
• the temperature of the battery, and very importantly…
• the charging network’s capacity

These days there are increasingly better apps that help you locate charging infrastructure at planned destinations. When you understand your car’s capabilities, you can better predict charging times and avoid overextending charging sessions. These apps are incredible tools that not only navigate you to public chargers—at highway stops, cafes, restaurants, shopping centers, hotels and more—they offer shared insights from other EV drivers who have used those chargers. They offer information such as whether chargers are available, what speed (level) they are, whether they are in service, or out of order and other useful titbits.

Five Facts About How Long It Takes To Charge Your EV:

✅ State of Charge (SoC) affects how fast your EV charges. Batteries charge fastest when emptier, and slower as they approach full. 

✅ The temperature of your battery affects your charging speed. Batteries like the temperature to be just right, and extreme temperatures can impact battery lifespan.

✅ Other loads in use while charging, such as cabin air conditioning or heating, can divert some of the energy destined for your battery.

✅ Batteries deteriorate over time and lose their charging capacity, particularly with frequent ultrafast DC charging. While charging to 100% on an AC charger is acceptable, with DC it’s a good idea to end charging around an 80-85% SoC to keep the battery from getting too hot and prolong its lifespan.

✅ Charging speed is determined by a negotiation between your EV’s voltage and current limits and the charger’s voltage and current limits.