Understanding EV Charging Speeds by Battery Size

EV charging speed is determined by two things: the power the charger can deliver and the maximum rate your car can actually accept. A larger battery pack generally takes longer to fill from empty, but cars with larger batteries often accept higher charging power too, which partially offsets that. The key is understanding that the car is always the limiting factor, not just the charger. Before anything else, make sure you have the right charging cable for your car, as using the wrong connector type will prevent charging entirely regardless of the speed available.

Why does battery size affect charging time?

Think of a battery like a tank of water and charging like filling it with a hose. A bigger tank takes longer to fill at the same flow rate. If two cars are both charging on a 7 kW wallbox but one has a larger battery, the larger one simply takes more time to reach full. This relationship is direct: charging time is roughly proportional to battery capacity divided by charging power. The calculation gives you an approximate number of hours, not a precise figure for any specific model, because real-world factors like temperature, battery management systems, and the state the battery is already in all affect the actual rate.

What limits AC charging speed?

When you charge using AC power, whether from a home wallbox or a public AC point, the rate is limited by the car's onboard charger. This is a component built into the vehicle that converts AC electricity from the grid into the DC power the battery stores. If your car's onboard charger is rated at 7 kW, it will draw at most 7 kW even if you plug into a 22 kW public charger. The extra capacity of the charger is simply unused. This is why upgrading your wallbox beyond your car's onboard charger rating gives you no speed benefit, though it can be worth doing if you plan to own a future car with a higher AC acceptance rate.

• A car with a 7 kW onboard charger: charges at up to 7 kW on AC, regardless of what the charger provides.
• A car with an 11 kW onboard charger: charges at up to 11 kW on AC, provided the supply can deliver that.
• A car with a 22 kW onboard charger: relatively rare, but charges at up to 22 kW on a compatible three-phase supply.

What limits DC rapid charging speed?

DC charging bypasses the onboard charger entirely. The charger delivers DC power directly to the battery. The limiting factor here is the car's maximum DC charge rate, which varies considerably between models. Some cars accept around 50 kW; others accept 100 kW, 150 kW, or considerably more. Plugging a car into a charger that exceeds its maximum DC rate simply means the car draws its maximum and the charger's extra capacity is unused. Conversely, plugging a car capable of 150 kW into a 50 kW charger limits it to 50 kW. Always check the charger power and your car's maximum DC rate before estimating how long a rapid charging stop will take.

What is a charging curve and why does it matter?

A charging curve describes how the rate of DC charging changes throughout a session. Most EVs start at their maximum DC rate when the battery is relatively low, then taper the rate as the battery fills. This happens because the battery management system reduces charge rate to protect cell health as capacity approaches its upper limit. Some cars maintain a high rate for a large portion of the charge, while others taper earlier and more steeply. A car with a flat charging curve will generally spend less time at a rapid charger for the same amount of energy added, even if its maximum rate is similar to another model. The charging curve is worth researching for any EV you are considering buying.

Why do most discussions focus on 10 to 80 percent?

Charging from 10% to 80% is the commonly quoted range for fast charging for one main reason: that is the window where most cars charge at or close to their peak rate. Above 80%, the battery management system typically slows the charge rate significantly to protect the cells. Filling the final 20% can take nearly as long as filling the first 70%, depending on the car. For long journeys, stopping to charge to 80% and then continuing is usually faster overall than waiting for a full charge. Most rapid charger pricing is also calculated per minute or per kWh, so understanding this helps you charge more efficiently.

How do I roughly estimate how long a charge will take?

A useful rule of thumb: divide the battery size in kWh by the charging power in kW to get a rough time in hours. For example, a 60 kWh battery on a 7 kW wallbox would take roughly eight to nine hours from empty to full. A smaller battery on the same wallbox would take proportionally less time. This is a general calculation to help you plan. Real-world times will vary based on starting state of charge, temperature, the car's charging curve, and how the battery management system behaves. Never rely on this estimate as a precise figure for any specific model. Consult the manufacturer's own charging data for accurate times for your car. If you need a wallbox-compatible cable, our range of Type 2 charging cables covers most home and public AC charging needs, and if you want a solution that travels with you, see our portable EV chargers.

Frequently asked questions

Does a bigger battery always mean slower charging?

Not necessarily. A larger battery takes more energy to fill from empty, but cars with larger packs often accept higher charging power too. The time to charge depends on the ratio of battery size to charging rate. A large battery on a high-power DC charger can sometimes charge faster in practice than a smaller battery on a slower charger, especially when you compare energy added per minute of charging time.

Will my car charge faster if I buy a more powerful wallbox?

Only if your car's onboard charger can accept a higher rate than your current wallbox supplies. If your car is rated at 7 kW AC and your wallbox is already 7 kW, upgrading to a 22 kW wallbox will not increase speed. However, a higher-rated wallbox may be worthwhile if you plan to buy a future EV with a higher AC acceptance rate, as you will not need to replace the wallbox again.

What is an onboard charger?

An onboard charger is a component built into the car that converts AC electricity from the grid into DC power the battery can store. Every EV has one. Its rated capacity, typically measured in kW, is the maximum AC charging speed the car can achieve. It has no effect on DC rapid charging, where power is delivered to the battery directly by the charger unit.

Why does charging slow down above 80 percent?

The battery management system deliberately reduces the charge rate above around 80% to protect the long-term health of the battery cells. Charging lithium-ion cells at high rates when they are nearly full causes accelerated degradation. The slowdown means the final 20% can take disproportionately long compared to the first 80%, which is why rapid charging sessions are usually planned to stop around that point on longer journeys.

Does cold weather affect how fast my EV charges?

Yes, significantly. Lithium-ion batteries charge less efficiently at low temperatures, and the battery management system will often limit charge rate to protect the cells when they are cold. Many EVs include a battery pre-conditioning feature that warms the battery before a rapid charging session. Using this feature, typically by setting a destination in the car's navigation, can meaningfully reduce charging time in cold conditions.

What is the difference between kW and kWh when talking about charging?

kW (kilowatts) is the rate of power flow, meaning how fast energy is being delivered. kWh (kilowatt-hours) is a measure of energy, meaning how much total energy is stored or transferred. Charging speed is measured in kW. Battery capacity is measured in kWh. To estimate charging time, you divide energy (kWh) by rate (kW), which gives you time in hours. The distinction matters when reading charging specs or comparing tariffs at public chargers.

Getting the most from your EV's charging capability starts with the right equipment. Browse our Type 2 charging cables for compatible home wallbox and public AC charging, or check out our portable EV chargers if you want a flexible option for charging away from a fixed wallbox. Not sure which cable fits your car? Use the reg checker on our home page to find the correct cable for your make and model, or visit our charging guides for more advice on getting the most from your setup.