With a reputation as Alberta’s hybrid and EV service experts, every day we enjoy fielding inquiries from EV owners all over Western Canada and the opportunity to provide them with honest advice. Over the past few months, many of those queries have been about DC (what we used to call level 3) charging speed. “My Hyundai Ioniq 5 is supposed to charge at 350 kilowatts; why am I only getting 68 kilowatts?”

There hasn’t been much education from car manufacturers about how DC charging actually works, so we’re writing this article to clear up some of the confusion.

Automakers advertise the peak charging speed, but every electric vehicle has a “charge curve”.

As its state of charge increases, your battery’s ability to accept a charge decreases. Therefore, almost every EV available today employs a charging strategy that slows the charge rate as your battery “fills up”. This is done to minimize the damage that leads to degradation (capacity loss) over time, along with other detrimental effects.

Let’s use our Lucid Air as an example. Lucid advertises a DC charge speed of up to 350 kW, but as we can attest – and as this excellent article from Inside EVs demonstrates – that only lasts until around 20% state of charge. By the time the battery is 50% full, the charge rate is already down to half of that. At 90% charged, we’re barely managing 50 kilowatts.

Other EVs exhibit the same characteristics. For example, a 2024 Ford Mustang Mach-E advertises a peak charge rate of 150 kW but that doesn’t even last until 10% state of charge. For most of the charge cycle, you’ll see speeds closer to 75 kW. The Volkswagen ID.4 advertises a charge rate of 125 kW and does manage to sustain that until around 30% state of charge, but the speed quickly falls off after that.

Battery temperature is extremely important.

It should be noted that the charge curves shown above are under ideal circumstances and there are other factors that affect your charge speed, the most prominent being battery temperature. If your battery pack is too cold, it won’t accept a charge nearly as quickly as on warm days. The difference can be drastic: a Tesla Model 3 that normally charges at up to 250 kW will only manage about 30 kW after sitting outside all day at -25 degrees C if the battery isn’t preconditioned before charging. What’s preconditioning? More on that next!

Very hot weather can affect charging speed as well, but not nearly as much – and most of the time, only if your car has a mechanical issue. We’ll explore some common issues later in this article.

Learn how to enable battery preconditioning on your vehicle.

Almost every EV features the ability to precondition the battery in order to achieve faster DC charging speeds. Most of the time, this means heating the battery. Preconditioning should usually start between 15 and 30 minutes prior to arriving at a DC charger. In extreme cold, some EVs require up to 45 minutes in order to reach their optimum battery temperature. Depending on the vehicle, preconditioning is commenced in different ways:

• Some vehicles allow you to start battery preconditioning manually, via a button or menu in their infotainment system.
• Some vehicles activate preconditioning automatically when the charger is set as a destination in their navigation system.
• Some EVs do both!

For vehicles that only support navigation-based preconditioning such as Ford and Tesla, it’s important to ensure that your navigation system recognizes the destination as a charger. To ensure that battery conditioning actually starts, be careful when setting your destination. For example, if you’re navigating to an Electrify Canada charger in a Save-On-Foods parking lot, set the Electrify Canada station as your destination, not the grocery store. In cases where it doesn’t recognize a charger, it’s sometimes possible to “trick” your vehicle into preconditioning by pointing the navigation system at a recognized charger nearby.

Sharing chargers can reduce your charging speed.

Have you ever wondered why you often see Tesla vehicles spaced out and using every second Supercharger – just like men using urinals, as the joke goes? That’s because older V1 and V2 superchargers are paired: adjacent chargers share the same power cabinet so when both chargers are in use, available power is cut in half. (Newer V3 and V4 superchargers have 1 megawatt cabinets that improve this, but the habits remain.) Similarly, many other public chargers work the same way. An Electrify Canada charger with two plugs can only output 350 kW in total, not 350 kW per plug.

Mechanical issues can hamper charging speed, too.

Every month we diagnose and repair mechanical problems that cause charging speed issues for our clients. Here are some common ones:

• During the summer, a plugged radiator can dramatically impede battery cooling.
• In vehicles equipped with a heat pump, low air conditioning refrigerant – usually caused by a leak somewhere – impedes battery heating and cooling during both summer and winter.
• A faulty battery heater may not warm the battery pack enough.
• A failed coolant valve may impede or totally disable battery heating/cooling.

If you suspect a mechanical issue with your electric vehicle, you’ve come to the right place. Explore our website to discover some of the reasons why My Garage is Alberta’s hybrid and EV service leader. Our elite team would love to provide an accurate, honest diagnosis.

The charger might be faulty.

If your vehicle is in perfect shape mechanically, your battery was preconditioned long enough and you’re still experiencing slow charging speed, there may be something wrong with the charger. Sometimes simply unplugging and plugging back in is enough to correct this, but you may have to try an adjacent charger as well. Apps like PlugShare are an excellent way to check for reported charger issues and to share issues with others.

Other DC charging tips from My Garage:

• On multi-day road trips, charge at the end of the day versus the beginning of the next. Following a drive, your battery pack will accept a charge faster than after sitting overnight.
• When it’s possible, “live in the the bottom half of your battery” to enjoy faster charging speeds. Many drivers find that making two quick stops adding 35% each time is actually faster than one stop with 70% charge.

Have another tip worth adding? Contact us!