October 8th, 2021 | E-Mobility
Speedy EV Charging is always a hot topic. Any new EV driver is interested in how long it takes to charge their new vehicle. So, let’s break down some of the questions about what factors affect EV charging speed.
Charging speed is often expressed one of three ways:
Given that the potential distance on a charge changes based on terrain, towing, wind resistance, and a range of other factors, Rate isn’t the best way to think about charging. So that leaves two:
|7 kW||30 kW||60 kW||120 kW||180 kW||360 kW|
|EVs with a small battery||50 (kWh)||4.17||1||30||15||10||5|
|EVs with a standard-size battery||70 (kWh)||5.83||1.4||42||21||14||7|
|EVs with a large battery||90 (kWh)||7.5||1.8||54||27||18||9|
A more realistic way to speak of EV charging is by power or time. Power is a little hard to express because the amount of power flowing into the battery changes throughout the charging process. So perhaps time is the best middle ground for talking about charging. How long does it take to charge a battery from 20% to 80%? I know that leaves out 40% of the charge possible, but there are good reasons for measuring this specific range. Read on to learn more!
First, there’s the vehicle. Different EVs charge at different speeds. For example, the Nissan Leaf’s top charging speed is 46kW, whereas the Porsche Taycan charges at up to 225 kW. They can’t take in any more power than that at any time. However, a lot of the time, they won’t even take it in that quickly.
Second, there’s the charger. An AC charger might charge at 7kW, whereas a large DC charger could charge at 180kW or even more. Different chargers have different speeds, and both AC and DC chargers come in a wide range.
Finally, there’s the grid. When a business installs a public charging station, that station plugs into a grid that can provide the power to run whatever size the station is. However, home chargers are different. If the capacity is lower than that of the charger, the homeowner may not always choose to undergo electrical upgrades to ensure the fastest charge possible.
Chargers come in two types: AC and DC. But what’s the difference? AC power is the kind provided by the power grid. DC power is the kind in the battery. AC chargers supply AC power to the vehicle, but onboard rectifiers aren’t very big and thus aren’t very fast when converting that power. DC chargers, on the other hand, have converters built right in. The result? Faster EV charging speeds because the car isn’t busy converting that energy!
I’m sure it comes as no surprise that larger batteries take longer to charge. Our small battery EV has a 50 kWh battery, compared to the largest car with a 90 kWh battery. Charging with the fastest DC fast charger listed, that’s a difference of only 4 minutes. However, with the smaller AC charger, the difference is more than 3 hours. Topping up at an AC charger is useful when you’ve got some time on your hands – at a restaurant, a grocery store, or a shopping center. They are also common at business parks, hotels, and apartments/condos. The goal of charging isn’t always to walk away with a full battery. Sometimes, it’s just putting a little more juice in because it’s convenient to do so.
EV batteries do better when kept neither empty nor full. They experience less degradation over time (although what they do experience isn’t much). As such, EV drivers are encouraged not to let their batteries consistently fall or spend time under 20%. If the EV battery is too low, charging speed is slower to help protect the battery.
When manufacturers and other companies test vehicle charging time and charging speed, they traditionally do so by charging the battery up to 80%. Why not to full? It’s because when the last 20% of the battery capacity charges up, the internal system slows the charging speed. This keeps the battery temperature lower and protects the battery. If drivers want to charge from 80%-100%, it’s best to do so overnight when there’s a lot of time available.
Ambient temperature also plays a role in charging speed. Batteries are most efficient when the temperature is neither too hot nor too cold. If the battery itself is too warm or too cold, the vehicle’s safety systems will protectively slow down charging until it comes to an appropriate temperature.
A range of factors affects how long it takes to charge an electric vehicle battery. Those factors include the vehicle charging speed, the power of the charger, the state of the battery, and even the temperature! The more drivers and charging providers know about battery charging, the better they understand how best to take care of the vehicles involved.
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