How long does it take to charge an electric car? Depending on your charger type and battery, it can take anywhere from 1 to 72 hours.
The great thing is, you can do the charge time calculation yourself, which I’ll go over.
Because charging time is a huge factor when it comes to EVs. It’ll definitely test your patience when you’re used to pumping gas in five minutes tops.
Surprisingly, many new EV owners quickly realize charging is super convenient. Even more so than going to their local gas station. You can charge your battery as you sleep in bed or sit back in your office.
It’s important to note though, the charge time of your battery depends on many variables. Just think of your phone battery. I’m sure you’ve found the charge time for your phone is never a constant.
Factors that affect an EV’s battery charging speed
The below 6 factors affect the time it takes to charge your EV’s battery.
#1 Battery size
The larger your battery, the longer your charge time. You measure your battery’s capacity in kilowatt-hour (kWh).
#2 Current battery charge level
Charging your battery from empty takes longer. If you’re topping up your battery from 50%, you’ll find the charge time greatly decreases.
#3 Max electric vehicle charge rate
Every electric vehicle has a max charge capability. When you connect your EV to most chargers, you provide Alternating Current (AC) to your car. While noting, your EV stores energy as Direct Current (DC) in your battery.
To convert AC power to DC power, your car uses an onboard charger (AC to DC converter). Different EVs have different rated onboard chargers. Let’s say your onboard charger has an 11kW rating. As a result, you can’t charge your car any faster by plugging it into a 15kW rated Level 2 charger.
Your onboard charger limits your charging capabilities with Level 1 and 2 chargers. And to keep cost and weight low, the onboard chargers of EVs always have limited power ratings.
Another way to view the max charge rate is in terms of amps, which is a function of power. For the Tesla Model 3, Tesla states,
“Maximum charge rate for Model 3 Standard Range is 32A (7.7kW) – up to 30 miles of range per hour.”
Important Note: DC Fast chargers charge fast. You’re no longer converting AC to DC using your car’s onboard charger. Instead, you use the charger’s industrial-rated AC to DC converter to charge your car.
But, there are still limits. Every EV has a BMS, Battery Management System. The BMS controls your charging session and tells the charger how much power to supply.
#4 Max charging rate of the charger
Different charger types have different power output ceilings. Let’s say your EV has an onboard charger rated 15kW. But if your charger’s power rating is 10kW, the peak charge will be no greater than 10kW.
#5 Battery tapering
The charge from low battery capacity to 80% is fast. But from 80% onwards, the charge slows down to protect the battery. This is because of the inherent characteristics of batteries. Even more, this battery charging profile is entirely controlled by the EV.
To visualize this charging profile, let’s use a crude water example.
Think of filling up a glass of water. Say you want to fill the glass to the brim without overflowing even a single drop. To pull this off, you’ll first turn the water faucet on full blast. Then, as the glass fills up, you slowly turn the faucet down to only get the last few drops of water you need.
#6 Weather conditions
Cold temperatures lead to longer charging times. This is because the electrochemical reactions in batteries are temperature-dependent.
Important Note: many EVs can combat the effects of cold weather. Some clever engineers designed in the warming of batteries before you charge. This allows for faster charging.
Learning the car charging units
Understanding the basics of electricity when it comes to charging is critical. More specifically, learning about kW and kWh.
These two acronyms you’ll see a lot when it comes to EVs. Where the k, kilo, is 1,000. So kW is 1,000 watts.
W = watts is a measurement of power. A watt is 1 joule of energy used or produced per second. If you turn on a 100-watt bulb, it’ll draw 100 joules of energy every second it’s on. So a 50,000-watt battery charger will charge a battery faster than a 10,000-watt battery charger.
kWh = kilowatt-hour is a measurement of energy. You can use kWh to show how much stored energy a battery has. For example, you can light a 1,000-watt bulb for 1 hour using a battery with 1 kWh of capacity.
The charge time calculation for an EV’s battery
The capacity of an EV battery we measure in kilowatt-hours of energy it can hold. For example, when you shop for an EV, you may see the following specified:
New vehicle model with the 82 kWh battery pack
Next, the rated charging power of a charger will allow us to determine the speed of a charge. The charging power we measure in kilowatts (kW).
Given this information, we can now calculate the approximate charge time for an EV. We’ll use the following formula:
Charge time =
Reviewing this equation, the charge time is equal to the battery size in kilowatt-hours divided by the charger’s power. The 0.87 is an approximation of an EV’s charger’s efficiency.
Tesla Model 3 Long Range charging calculation using a Level 2 charger
Let’s calculate the charging time for a Tesla Model 3 Long Range with an 82 kWh battery. We’ll charge the Model 3 using a Level 2 charger rated 7 kW.
Charge time = = 13.5 hours
Thus, charging the battery from empty to full capacity will take 13.5 hours.
Tesla Model 3 Long Range charging calculation using Tesla’s V3 Supercharger
According to Tesla,
V3 is a completely new architecture for Supercharging. A new 1MW power cabinet with a similar design to our utility-scale products supports peak rates of up to 250kW per car.
You’re never going to get the peak power of 250kW over your entire charge. The power naturally tapers off as the battery charge increases. So, the 250kW peak may only last for a few seconds.
To illustrate this charging profile, the below table shows the data for peak power versus charging time. I used data of charging using a 250kW DC fast charger. You can see how over time as the EV charges, the peak power decreases. This is a very typical charging profile.
|Charging Time||Peak power|
|5 minutes||245 kW|
|15 minutes||225 kW|
|20 minutes||200 KW|
|30 minutes||135 kW|
|40 minutes||85 kW|
|50 minutes||50 kW|
|60 minutes||35 kW|
Now for sake of simplicity, let’s assume an average peak demand of 100kW over the entire charge. This is a reasonable estimate.
Charge time = = 0.94 hours
Thus, charging the battery from empty to full capacity will take almost 1 hour.
Important Note: the peak power output varies on your charger. The following are the peak power values from chargers you’ll commonly come across:
- Level 1 charger: 1.92 kW
- Level 2 charger: 12 kW
- DC fast charger (Level 3 charger): 250 kW
Each charger type will have a varying charging cost too.
“How long does it take to charge an electric car?” wrap up
Many factors affect the charging time of EVs. No different than charging your smartphone.
By using the charge time calculation though, you can ballpark your EV’s charging time. This way, you can properly plan ahead on when and where to charge.
Plus, you’ll better know what type of charger to install in your home, given your driving habits.
What EV do you have and how long does it take you to charge? What tips do you have for charging your EV?
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Koosha started Engineer Calcs in 2020 to help people better understand the engineering and construction industry, and to discuss various science and engineering-related topics to make people think. He has been working in the engineering and tech industry in California for over 15 years now and is a licensed professional electrical engineer, and also has various entrepreneurial pursuits.
Koosha has an extensive background in the design and specification of electrical systems with areas of expertise including power generation, transmission, distribution, instrumentation and controls, and water distribution and pumping as well as alternative energy (wind, solar, geothermal, and storage).
Koosha is most interested in engineering innovations, the cosmos, our history and future, sports, and fitness.