Do fast chargers stop at 80%?

09 Apr.,2024

 

Ever plugged in your EV and returned later to find it's still only 50% charged? Us to. It can be frustrating when your EV is charging slower than it used to. You may also worry about damage to the battery or the charger. While that's a possibility, there are several other reasons why you're previously super-fast charging is getting slower.

Here are 6reasons why your EV isn’t charging as fast as before (and how to fix them).

Cause #1 - Battery degradation

Like the battery in your phone or laptop, your EV battery can degrade over time. This means that it's unable to cope with the high charge rate, which results in slower charging times. While this is fine if you're leaving your vehicle overnight, it can cause problems when you want a rapid roadside top-up.

Solution: EV battery degradation is normal. The more times that you charge your EV car battery, the less efficient it is. While there's no way to fix the issue (aside from replacing the battery), there are ways to maximize your EV battery lifespan. You should follow the recommended charging processes and avoid deep discharges (where you almost empty your battery of charge).

Cause #2 - State of charge

Your battery's state of charge (SOC) can determine how quickly it charges. When your battery is empty, your battery will charge the fastest. As it gets fuller and fuller, the charge rate slows down. For example, it can take as long to get from 0-50% as it can to get from 50-75% charge.

You may find your battery only charges to 80% and then stops (or creeps up very slowly). This is because it can take as long to charge from 80-100% as it does getting from 0-80%.

Solution: Lithium-ion batteries don’t like to be fully charged or fully discharged. Instead, they’re at their most efficient in the mid-range. If your battery isn't getting to 100%, don't worry. Instead, aim to keep your battery mid-range for optimum performance and longevity. Sometimes, it can't get to 100%, and that's just fine.

Cause #3  - Charging infrastructure issues

Not all charging stations are equal. If your EV is charging quickly at home but not at work, it could be because the station isn't as efficient. In some cases, the charging station's power output may be lower than your EV's maximum capacity, which can mean slower charging.

You may also find that charging speeds can drop when multiple vehicles are connected to a charging station.

Solution: Unfortunately, you can do little to improve charging station efficiency. You will simply have to find somewhere comfortable to sit and wait. If you are going to have to use a less-efficient charger, or one with multiple connections, plan ahead and give yourself some extra time to top-up

Cause #4  - High temperatures

We all love the sun, but sadly our EV batteries don’t! Extreme heat can have a massive impact on battery performance and limit its ability to accept a high charger ate. Why? It's all about safety. The intelligent charging system inside your EV constantly monitors its battery's health, stability, and safety. Rapidly recharging a warm battery could lead to overheating and an incredibly dangerous phenomenon known as thermal runaway, where the battery pack combusts.

Solution: You can't control the weather but can control where you park your car. Leaving it in a shady spot(under a tree or in a garage) can help lower battery temperatures. In sweltering temperatures, you may want to consider pre-cooling the battery before charging.

Cause #5  - Software limitations and upgrades

EVs are packed full of technology that is responsible for managing charging and maintaining the battery. Manufacturers regularly update their software to optimize how their vehicles operate, and you don't have a choice whether you want it or not.

Sometimes, EV builders will change the charging algorithms, affecting recharge speed. The updated software may prioritize battery health over charging speed, for example.

Solution: Stay up to date with all details on your EV software! While you don’t have any choice in the software your vehicle runs, they may provide information and advice along side details of updates that can help you to improve your vehicle’s charging performance.

Cause #6  - Faulty charging equipment

Yes, it can happen that you plug your EV into a charger that’s broken or faulty. Common causes of slow charging are damaged cables and connectors. It’s more likely to happen in high-use charging stations, such as those at offices or at service stations.

Solution: EV charging stations are complex pieces of machinery that deal with huge amounts of electrical power. If you notice a damaged charging station, safely unplug your car and inform someone. If a station is broken, the simple solution is to find another one (we hope you've got enough charge left to get there!).

Protecting your battery

The battery in your car is the most expensive component in your EV and one of the most fragile. After investing in an EV, you must learn how to care for your battery, optimizing its charging for maximum efficiency. Understanding the factors that can affect charging speed is essential for diagnosing the problem and finding a solution. In many cases, you'll simply have to wait a little longer for an EV charge, but we think it’s worth waiting for.

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.


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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.

 

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Do fast chargers stop at 80%?

The 80% rule: Why you shouldn't charge your EV to 100%

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