By Craig Cole, Senior Editor, EV Pulse
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This blog was originally posted two years ago, yet it continues to garner enormous attention and visits. In fact, it's our most visited blog post! Why? As interest in electric vehicles continues to grow, fleets and consumers are looking for clear and concise articles that help them understand how to manage the transition from gas to electric. From the initial consideration to transition to EV to the buying process, and then to the day-to-day implementation, there are a lot of decisions to be made. This article helps EV owners understand how to get the most from their battery and extend its life. We hope it helps you.
Let us know if there are other areas of EV ownership you'd like us to uncover.
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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 , 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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Let's face it ' for many people, when it comes to charging electric vehicles, there is a whole lot of confusion.
When it comes to installing electric vehicle charging equipment, there are many things to plan and consider. For instance, you'll need charge points, branch circuits, circuit breakers, and more. Then there's the issue of responsibility. Who is actually in charge of electrical systems? Who is testing the hardware and setting standards for 'behind-the-meter' installations?
The good news is ' it doesn't need to be confusing.
This article will help you cut through the information overload out there and answer the critical questions.
If you want to learn more about energy management and smart charging, download our new report, "Energy Management 101: How to Efficiently Charge Electric Fleets".
What is The National Electric Code (NEC)
In the US, the NEC provides useful guidance on electric vehicle charging. The NEC started as a very broad description of how to design electrical systems. It didn't venture into installation and operation guidance, especially not when it comes to electric vehicle charging.
Fast forward to today, and the NEC has been adopted in all 50 states of the US and has become one of the most important benchmarks for electrical design, installation, and inspection to protect people.
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Why the NEC standards matters for your EV charging project
So, what has made the NEC a key part of the safe installation and operation of EV charging projects? The NEC introduced a new section that specifically describes how to install charge points and Electric Vehicle Supply Equipment (EVSE).
'The electrical conductors and equipment, external to an electric vehicle, that connects an electric vehicle to a supply of electricity by conductive or inductive means, and the installation of equipment and devices related to electric vehicle charging.'
- NEC part 625 (Electric Vehicle Charging and Supply Equipment Systems), edition
Ok, so that's a long sentence and may seem a bit confusing. But what the NEC is trying to say is that Part 625 of the code describes the standards on how to connect EVs and charging stations.
This is especially relevant to the design of a charging location, fleet depot, or any location to charge up your electric vehicles.
It doesn't tell you which equipment to use. You'll need to decide which equipment works together and strictly follow the NEC rules.
80% vs. 100%-rated Circuit Breakers
The NEC code is massive. Luckily, we're not interested in the whole thing!
We're going to focus on the sections that are relevant to EV charging stations, specifically sections 625.40 and 625.42, which set out rules on how to apply load management with EVs. Section 625.40 states that each outlet used to charge EVs needs to be connected by an individual branch circuit. A branch circuit is an electric circuit extending beyond the last circuit breaker. The branch circuit starts at the breaker box and runs to the EVSE (charging station).
Up until , the NEC required that every charge point has a dedicated circuit rate of 100%. 'Oversubscription' was not permitted. But, as charging points don't usually require full power, the rule was changed in . This gave rise to the additional section 625.42 with revised guidance.
The 80% rule and why it matters for EV charging
Section 625.42 describes how to rate the load of EV charging. This is relevant if you plan to install more chargers than technically 'possible.'
It states that
'Electric vehicle charging loads shall be considered to be continuous loads.'
Continuous load means that the maximum current is expected to continue for 3 hours or more. Therefore, non-continuous applies to everything else. In other words, anything less than 3 hours.
This is the tricky part of figuring out.
If all your EV loads are non-continuous, you wouldn't need to worry about oversubscribing, and you can just size your breakers for 100% of your load. But, if your EV loads are continuous, you need to follow the 80% rule. This states that continuous load must be 20% below the breaker capacity.
Why can you oversubscribe charging stations on breakers?
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If you have to treat EV load as a continuous load, how can you install more EV capacity than 80% of your panel breaker? Wouldn't that violate the rule?
No. Here the next paragraph is important.
Section 625.42 also states:
'Where an automatic load management system is used, the maximum equipment load on a service and feeder shall be the maximum load permitted by the automatic load management system.'
In other words, when you want to run charging stations above 80% of line capacity, you must have an intelligent load management system to maintain control of the loop/loads. This load management system sets limits on the charge point (EVSE) and thereby ensures the 80% rule. You can now oversubscribe breakers.
The good news is that power management software such as Ampcontrol can be set to intelligently split the power at a circuit, panel, site, or transformer level.
Software like Ampcontrol can also combine any of those elements, in which case it will ensure that the load limit is never exceeded at any level. This ensures that the '80% rule' is always followed.
To select your breaker for continuous loads, you need to determine the load on each branch circuit, then calculate the required ampere.
But, you can't just take 100%. You always need to follow the '80% rule.'
The upshot of all this is that, with Ampcontrol, you can install an average of 40% more electric vehicles and EV charge points per location.
Summary
Hopefully, this article has cleared up some of the confusion surrounding EV charging. To wrap up, here are the main points again:
- EV charging installation can be confusing, especially when it comes to an understanding of the standards, best practices, and responsibility for testing.
- In the US, the NEC's latest version includes a comprehensive section on EV charging installation and maintenance ' section 625.
- Sections 625.40 and 625.42 describe the conditions for installation for continuous and non-continuous loading.
- The 80% rule is the one you should try to follow for EV charging.
- When the load is managed by smart charging software such as Ampcontrol, you'll be able to install 40% more EVs and charging points per location.
- Load management like Ampcontrol allows you to oversubscribe charge points on breakers.
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Read more about smart charging here: What is Smart Charging for Electric Vehicles?
For more Ev Solutions Charging Stationinformation, please contact us. We will provide professional answers.
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