EV charging stations are becoming more commonplace. Most charging stations you see are AC chargers. Until recently, AC chargers have been the only option. But in recent years new technology known as DC Fast Chargers has been developed allowing companies to apply a different type of technology to charge vehicles faster than the standard AC chargers
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The proportion of DC fast chargers to AC chargers is growing. But for many people, the question remains AC vs DC EV charging, which charging station should be used for fleet vehicles? Should companies with depots install AC chargers or DC chargers? That’s the question we’ll seek to answer in this article.
To help introduce you to the world of AC vs DC and their differences, there are two key things to remember:
AC and DC operate differently. They flow in different ways, serve different purposes, and impact charging speed and efficiency in unique ways.
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Alternating current (AC) power can be described simply as the standard electricity that comes out of power stations and travels along power lines to homes and other buildings, sometimes referred to as mains or utility power.
Direct current (DC) power, as the name suggests, is the electric current that moves in a straight line.
Direct current can come from multiple sources, including batteries, solar cells, fuel cells, petrol generators, and some modified alternators. DC power can also be "made" from AC power by using a rectifier that converts AC to DC.
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Your outlet delivers AC power, and your vehicle battery needs DC power.
The only way to achieve this is to convert AC power into a DC power output. This is what we call an AC to DC converter (AC-DC converter).
AC EV Chargers require you to build this converter into your vehicle. This means that the vehicle has its own small AC-DC converter. So, the vehicle receives AC power from the charge point, then the vehicle converts it to DC power.
DC EV Chargers require you to build this converter into your charge point. This means the chargers have their own built-in AC-DC converter, and the vehicle receives DC power directly. No conversion is required inside the vehicle.
The key difference between AC and DC charging curves lies in how much power the battery can accept over time.
AC chargers rely on your car's built-in converter, which typically handles a constant power level. This translates to a flat charging curve on a graph. The car steadily charges the battery at a set rate until full.
DC fast chargers have a more powerful converter and deliver DC power directly to the battery. However, for battery health reasons, the ideal charging rate isn't constant. DC charging curves typically start high, allowing for rapid initial charging. As the battery fills up, the curve slopes downward, reducing the power input to prevent overheating. This creates a decreasing, curved line on a graph.
Batteries need DC power. And there is a simple reason. Just like any other battery - a car battery uses and provides DC power. This means the load flows in one single direction and is stored using a chemical process.
As mentioned, AC current changes direction periodically. To store AC, a battery’s terminal needs to change polarity (+ and -) at the same speed, which is not possible. Connecting an AC supply to a battery to store AC power means the battery charges only during the positive half-cycle and then discharges during the negative half cycle.
In other words, there is no way a car can store AC power in a battery.
The faster you want to charge a battery - the more power you need to provide. Fast charging is usually above 50 kW, and slow charging typically between 1-22 kW to provide more power when charging a battery, you need a much larger AC-DC converter.
The problem is - converting high power from AC and DC is expensive. A large converter easily costs USD 10,000.
This high-power charging is best carried out with the converters built into the charging station rather than the vehicles so you’re not dragging around heavy and expensive converters dragged around with you in your car.
That’s the main reason why DC chargers appear to be faster than AC chargers. They aren’t really any faster; it’s just much easier and cheaper to generate high-power DC output within the charger rather than convert the output from an AC charger in the vehicle itself.
AC charging is best for regular charging needs such as:
DC chargers cost a lot more than AC chargers. DC chargers require more space and require much more complex spare parts to facilitate processes such as active cooling.
In addition, high power charging requires a high power connection to the grid. With a typical residential grid connection, you won’t be able to install a DC charger.
DC fast charging is best for situations where time is tight such as:
The rule of thumb is: Install DC chargers when you need fast charging and install AC chargers when you don’t.
DC fast chargers are ideal for charging EVs that need to be back on the road quickly. But they are more expensive to install and maintain than AC chargers.
If time is of the essence for your fleet, then DC chargers are going to be the best option.
If you have a mixed fleet of vehicles - i.e., some that need fast charging and some that don’t, then a mixture of AC and DC chargers is best.
Either way, smart charging software for electric vehicles can help fleet managers to offset some or all of the extra initial outlay by reducing ongoing energy costs.
Read more about AC and DC charging here: How to mix AC and DC charging stations?
10 Min. Read
Are you considering purchasing an electric vehicle (EV) or are you already an EV owner looking to maximize your EV experience and get the most out of your vehicle?
While you may be used to driving an internal combustion engine (ICE) vehicle, driving an EV will mean navigating unfamiliar terminology and specifications such as voltage, amperage, or battery capacity. This can be challenging, however, understanding these details is essential for maximizing your vehicle’s performance and taking full advantage of all that your EV can do.
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In this article, we’ll take a closer look at vehicle and charger amperage to explore and understand your EV’s charging process, plus how to match your EV charger’s capabilities to your EV for optimal efficiency. We’ll also discuss the differences between Level 2 and DC Fast charging, also known as DCFC or Level 3 EV charging, to ensure you can make the most informed and practical charging decisions when it comes to driving electric.
Amperage refers to the flow rate, or volume, of an electrical current. In the context of your EV, your vehicle’s amperage represents the maximum amount of the AC current capable of passing through the onboard charger to your battery.
Amperage ratings for electric vehicles have historically ranged anywhere from 16 to 80 amps, but most recent models can accept between 40 to 50 amps. Amperage is an important consideration when choosing an EV since it directly impacts the amount of power your EV can accept, and thus, also has a direct impact on charging times and the power of the charger you can use.
The higher the amperage rating, the faster you can potentially charge your EV, provided that the charger can match the EV’s capacity.
If you currently own an EV, familiarizing yourself with your vehicle’s amperage rating will help you better understand the charging capacities of your car and help ensure you are selecting an optimal charging solution.
You can easily find your vehicle’s amperage in either your owner’s manual or by simply looking up your EV’s make and model on the manufacturer’s website.
Now that you are familiar with electric vehicle amperage, it’s important to understand EV charger amperage as well. This refers to the maximum flow of current the charger can draw from the grid and supply to your EV. It’s important to understand your charger’s amperage capabilities, as they can vary significantly depending on the charging level.
Level 1 charging, which uses a standard 120V outlet, typically provides a flow rate of 12 to 16 amps.
While this is sufficient for charging a plug-in hybrid electric vehicle (PHEV) in approximately 5-6 hours or topping off an EV battery, it results in slow charging times of over 40 to 50 hours for battery electric vehicles (BEVs), which have a larger battery capacity and solely rely on electricity to operate, to fully charge.
Level 2 charging ranges from 15 to 80 amps, with hardwired chargers typically delivering a higher flow rate than portable models. A Level 2 charger will typically take about five hours to fully charge your EV but can take up to ten hours depending on the capacity of the charger and the size of the EV battery.
You should also note that amperage not only affects charging speed but can also impact the cost and installation requirements of the EV charging equipment.
To ensure the long-term safety and efficiency of an EV charging station, a qualified electrician must install a circuit breaker with a capacity 25% higher than the charger’s amperage. So, for example, if you are looking to install an 80-amp EV charging station in your home, your electrical panel would need the capacity both in electrical load and physical space, to add a 100-amp breaker to support the EV charging station.
Lastly, DC Fast charging stations, or Level 3 EV chargers, deliver the highest amperage as well as the fastest charging times—often fully recharging an EV in about an hour.
These commercial-grade chargers, which are not available for residential use and generally cannot be used by PHEVs, can deliver anywhere from 100 to 500 amps, depending on the make and model of the vehicle.
This is the most expensive form of EV charging and is best for when you are driving longer distances, such as a road trip.
One key difference between DCFC and Level 1 and Level 2 EV charging is that DC Fast Charging stations already provide electricity as a DC current instead of an AC current. This is more efficient as the EV will not need to convert the electricity to a DC current to store within the onboard battery.
So what happens if your EV charging station and EV have different amperage capacities?
You might wonder if this means you are only able to charge your EV with a charger that has the same amperage and fortunately, this is not the case.
Even if the amperage of your EV charging station and EV are different, your EV will still charge, but you may run into some limitations.
If your EV has a higher amperage rating than the charger you’re using, the charger capacity will limit the flow rate of the current that can reach your EV.
This type of charging mismatch results in a charging speed that is slower than your EV’s capabilities, which can be inconvenient and doesn’t help you get the most out of your EV.
Keep in mind your daily driving needs and mileage will impact the actual amperage needed as well.
If you’re driving significantly less than your vehicle’s range each day or only use your vehicle occasionally, you may not need a charger with the maximum output that your vehicle can accept and it may be more affordable to install a home charger with a lower amperage than your vehicle’s maximum capacity.
Even if you plug your EV into a charger with a higher amperage, your EV’s onboard charger won’t draw current with a flow rate that is higher than the vehicle’s capacity.
Thanks to your EV and EV charger’s ability to communicate and adjust the current flow rate, there is no risk of damaging your EV when using a high-amperage charger. However, you should know that even though they are rare, malfunctions can happen—especially if any charging components are damaged.
The main issue with using an EV charger with an amperage rating much higher than your vehicle is that you could be overpaying for charging. If you’re considering upgrading your home with a Level 2 EV charger, investing in a high-capacity model could cost more than you would otherwise need to spend, especially if your vehicle isn’t able to utilize the charger’s full power output.
If you’re charging your EV at a public EV charging station, spending more for DC Fast charging might not necessarily be the best option if your vehicle won’t charge faster than its top amperage capacity. Additionally, some public charging locations will offer charging stations with different amperage outputs and you may be able to use a lower output charging station with no impact to the speed of recharging your EV—ensuring the higher-powered EV charging stations are available for other drivers whose vehicles have a higher amperage capacity.
Alternatively, if you have an EV with a relatively low amperage, a public Level 2 EV charging station may also be fully adequate in helping you achieve the fastest possible charging speed and DCFC may be unnecessary, as is the case with most PHEVs and some older BEV models.
To further put this into perspective using the example above of an 80 amp charger requiring a 100 amp breaker, it is often more expensive to install a high-powered Level 2 EV charging station at home. If your EV is only able to accept a maximum capacity of 48 amps of AC current, installing an 80 amp at-home EV charger is unnecessary and you would be better served by installing a 48 amp charger that only requires 60 amps of breaker capacity.
However, if you are looking at future-proofing your charger in anticipation of any future EVs, you may still want to install a more powerful EV charger, but remember that it will not mean a faster charger for your current vehicle.
While opting for a Level 2 EV charging station with a significantly higher amperage may have you overpaying, there is something to be said for investing in an at-home charger with an amperage that exceeds your EV’s charging capacity.
With each generation, EVs are being designed with better performance and higher amperage ratings. Additionally, manufacturers are increasingly offering powerful electric trucks and SUVs with high-capacity batteries, making a future-proof charger a smart long-term investment.
When choosing a Level 2 at-home EV charging station, you should consider your future needs and next EV purchase. While your EV charger should match your current EV’s charging capacity, it may make the most sense for you to invest in a charger that can deliver a slightly higher amperage to anticipate a future upgrade to a more powerful EV—especially if you plan to live in your current home for many years.
Because chargers that support a higher flow rate can often require upgrades to your existing electrical infrastructure, whether for a panel upgrade or load-calculation device, a one-time investment can be more cost-effective than paying for future upgrades after the initial installation.
Here are a few things to keep in mind when choosing an EV charging option:
When researching amperage ratings for your EV or EV charging products, it’s essential to rely on reputable sources. The manufacturer’s website is the best place to start for accurate, up-to-date information.
A certified and trusted EV charger installer can answer all your questions about amperage, review your realistic charging needs, and recommend a charger with an amperage rating that aligns with your vehicle and daily driving habits.
Amperage is an important aspect to consider when finding the best charging solution for you and your EV. Ideally, your EV charger amperage should be equal to or slightly higher than your electric vehicle’s amperage rating so you can optimize your charging speed and opt for a cost-effective charging solution.
When it comes to installing an EV charging station at home, deciding which EV charging station you’re going to install can be a big decision, but finding a qualified EV charger installer shouldn’t be one and the best way to choose the right charging product is to get help from a qualified installer.
Qmerit can help. As North America’s most trusted EV charger installation partner recommended by automakers, EV charger manufacturers, utilities, businesses, and homeowners alike, Qmerit’s network of licensed electricians has installed over 770,000 EV charging stations and can help you evaluate your needs to purchase and install an EV charging station that optimizes your EV experience.
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