By Craig Cole, Senior Editor, EV Pulse
There are rules for everything. Pay your taxes… wear pants… don’t drive on the sidewalk … and if you own an electric vehicle, you need to be aware of the “80% rule.” Why is 80% an important number if you own an electric car, crossover, or pick-up?
There are two reasons: charging performance and battery longevity. Most of the time you should only charge an EV to 80% because charging rates slow down dramatically past the 80% mark. And two, the long-term health of your vehicle’s battery pack is improved when kept below 100%.
What does all this mean?
Concerning charging rates, a good example is the Hyundai Ioniq 5 with the optional, long-range battery. This hatchback-like crossover can DC fast charge from 10 to 80% in an incredibly quick 18 minutes. But it needs an additional 32 minutes to go from 80 to 100% - almost twice as long as it took to go from 10 to 80.
Why? Charging is not linear. Instead of batteries taking in energy at a constant, predictable rate, the rate actually changes based on a myriad of variables, though most importantly, the battery’s state of charge. Simply put, the fuller the battery is, the slower it absorbs energy. Imagine if a conventional car’s gas tank took longer and longer to fill up the closer it got to being full. It's kind of crazy.
The best analogy I’ve heard for why charging slows down is that batteries are like theater seating. When you’re one of the first people to enter, it’s quick and easy to find a chair – you can sit anywhere – but as the theater fills up, it takes a lot longer to snag a spot and sit down. In the Li-MAX Cineplex above, the electrons are climbing over each other and spilling popcorn everywhere!
It’s important to know about the “80 % rule” if you’re on a long-distance drive in an EV. When it’s time to charge, it’s often smarter to stop at 80% and then get back on the road, instead of waiting for the battery to completely fill up. Doing so maximizes your use of time.
For example, if your EV has 300 miles of range when fully juiced up, that means it can go about 240 miles with an 80% state of charge. (Obviously, you’re going to stop and power up before hitting zero miles, but let’s keep things simple and say 240.) If the 0-to-80% recharge time is 40 minutes, you can hit the road in little more than half an hour. If you want to fully replenish the battery, it could realistically take an additional 90 minutes to go from 80 to 100%. In the time it took you to gain that extra range, you could be a hundred miles or more down the road and in the vicinity of another charger. That’s why stopping at 80% usually makes the most sense (though that is something YOU have to determine).
There are, of course, instances where you’ll want to wait longer to hit 100%. Maybe there are huge distances between DC fast chargers, and you need every bit of range you can get. It could be the dead of winter and you have range anxiety about making it to your destination. Or you’re towing a car or boat, and the extra weight means you need the additional kilowatt-hours to get you to the next charging station.
The other reason to avoid going all the way to 100 is because it can help preserve battery life. Whether it’s a phone, cordless drill, or your car, batteries simply don’t like to be full. Keeping them topped to the brim means, over time, the maximum kilowatt-hours they can hold shrinks faster than it would otherwise. Always concerned about warranty costs, automakers even suggest limiting how much you charge. Car companies make this easy to do with an infotainment system that allows you to set your preferred charge level – even when you’re not at home.
It’s important to note that you can charge your EV to 100%, but it’s just that for optimal battery life over the long haul, charging to a lower percentage is a good idea. It’s like changing engine oil in an old-school vehicle. You can follow the manufacturer’s recommendation, but doing it more frequently is never a bad idea, especially if you plan on keeping your car or truck for years and years.
More related blog posts
How WiTricity Makes Charging EVs Easier
What's It Like to Charge an EV Wirelessly
The Role EVs Can Play to Save the Power Grid
Craig Cole is Senior Editor at EV Pulse. He brings 15 years of experience to EV Pulse and is a proud member of the Automotive Press Association and the Midwest Automotive Media Association. Check out the EV Pulse YouTube channel here.
FAQs
There are two reasons: charging performance and battery longevity. Most of the time you should only charge an EV to 80% because charging rates slow down dramatically past the 80% mark. And two, the long-term health of your vehicle's battery pack is improved when kept below 100%.
Is it better to charge EV to 80 or 100? ›
Never let your battery sit at 100% charge. Generally speaking, lithium-ion batteries do best when they operate in the 30%-80% charge range.
Is 80% better than 100% charging? ›
No batteries last for ever, of course, but staying proactive and aiming for 80% charge can help them last longer. This is because the battery finds it easier to charge when it is slightly empty, rather than nearly full, and therefore has less stress within its charging cycle.
What is the 80% rule for EV charging? ›
The 80% rule for EVs suggests that it's often recommended to charge electric vehicle batteries up to 80% of their full capacity. This is because charging speeds significantly slow down beyond the 80% mark.
What is the best charging percentage for EV? ›
Simply, the 20-80% rule suggests keeping the battery of an electric vehicle charged between 20% and 80% of full capacity.
Why shouldn't I charge my EV to 100%? ›
There are two reasons: charging performance and battery longevity. Most of the time you should only charge an EV to 80% because charging rates slow down dramatically past the 80% mark. And two, the long-term health of your vehicle's battery pack is improved when kept below 100%.
Should I charge my Tesla to 80 or 100? ›
Recurrent always recommends keeping lithium ion batteries between 30% and 80% state of charge, regardless of their specific battery chemistry.
Should I charge my EV every night? ›
Keeping the charge between 20% and 80% is often recommended to extend battery life. Charging your EV every night regardless of the battery's remaining charge means more frequent use of electricity.
Should I run my EV battery down before charging? ›
If needed, use a level 2 or level 3 fast charging station to supplement your charge on the go. You might also be wondering, “Should I run my EV battery down before charging?” In short, no. Like gas-powered cars, electric vehicles should never “run on fumes” as it can reduce your EV battery lifespan.
Is charging a battery to 85 or 100 better? ›
Most people charge it up to the max 100% as it's intended to do, charging only to 85% means you get less hours to compared to %100 and need to recharge sooner. The more you charge the more life of the battery goes down which isn't good.
Typically, public rapid chargers offer between 43kW and 350kW. A rapid charger of 50kW would take 30 minutes to charge a 42.2kWh BMW i3 from 20% to 80% – adding 72 miles. If your car has a larger battery, for example a 77.4kWh KIA EV6, it would take 54 minutes to get up from 20% to 80% – giving you roughly 150 miles.
What is the etiquette for EV charging? ›
Instead, only park at a charging station when you're actively charging, and move your car off the station once your app tells you that charging is complete, or you've reached your targeted level of charge. Resist the temptation to think of an EV charger as an open parking spot.
Why does ChargeNet only charge to 80? ›
ChargeNet offers the choice to only fill to 80% as the default option because the slower you charge, the more it will cost you. ChargeNet does not allow you to charge over 95% because that last 5% may take as long as the first 95%, for only a few kilometres' gain.
Should I charge my EV to 80 or 100? ›
And while it's perfectly safe to charge your electric car to 100%, the Lithium-Ion batteries that power most electric cars are most efficient working in ranges from roughly 20 to 80%.
What is the most efficient way to charge an EV battery? ›
Fully charging your battery every so often doesn't cause an issue. But regularly charging to 100% will affect long-term battery health. Instead, the best way to extend EV battery life is by depleting it to 20% and then charging it up to 80%. This is because of the way the battery works.
What is the best battery percentage for charging? ›
So at what percentage should you charge your phone? The best practice for preserving phone battery health is to plug it in at around 20% and charge it up to 80-90%. This is especially important if you use fast charging, as charging from 0% will cause a lot of heat, and from 80% up, fast charging becomes less efficient.
Is it better to charge to 80% or 100% on an iPhone? ›
Battery Health Catch 22
You want your battery to last for as long as possible before you have to replace it, but the best way to do that is to only charge the battery to 80 percent.
Is charging EV to 90% OK? ›
It's all to do with keeping your battery as healthy as possible, for as long as possible. And while it's perfectly safe to charge your electric car to 100%, the Lithium-Ion batteries that power most electric cars are most efficient working in ranges from roughly 20 to 80%.
What level of EV charging is recommended? ›
We recommend the use of a Level 2 charging station for all electric vehicles and plug-in hybrids, to enable you to charge faster and get the most out of your EV's charging capacity.
What is the best voltage to charge an electric car? ›
If you own or plan to own an EV you'll be wise to consider having a 240-volt Level 2 charging solution installed in your home. A typical Level 2 connection is 240 volts and 40 to 80 amps.
