Video: Why You Need to Know the Charge Rate of Your EV

Electrify America charging station
Credit: Roberto Baldwin/SAE


As the sales of EVs continue to rise so will the use of EV charging stations. Fortunately charging station companies are working towards increasing the reliability of these stations. That should reduce charging frustrations. But, there is another source of charging irritation, a slow-charging vehicle using an ultra-fast charging station. 

The charge rate of a vehicle is the rate at which it can accept electricity. It also determines how long it will take a vehicle to charge. 

For example, let's say a vehicle can charge at up to 50kW. The battery capacity of the vehicle is 100kWh and that delivers 300 miles of range. In one hour, under ideal conditions, the charging station will add 50kWh to the battery and add 150 miles of range. 

The odd thing is, that some automakers don't surface the charge rate of their vehicles and instead talk about how quickly a vehicle can charge from say 10% to 80%. It's a helpful metric, but it's not the whole story. Without that charge rate information, some EV owners are unaware that at charging locations with mixed charging stations, they might be plugging into a station that's beyond (or even below) the capabilities of their vehicle. 

For instance, if a Chevy Bolt that supports DC fast charging at up to 50kW pulls up to a charging location with DC fast chargers rated at 150kW and 350kW, it should (if possible) plug into the 150kW station. Plugging into the 350kW station with that Bolt will not make that vehicle charge any quicker. Instead, what happens is a vehicle that supports charging above 150kW, for example, a Kia EV9 might pull up and is now forced to use the slower 150kW station even though, it can benefit from the additional speed of the 350kW station. 

This becomes an even bigger issue when a charging location is outfitted with 50kW charging stations. 

At its core, the issue is about the combination of charging rates and battery capacity. The Chevy Silverado EV can charge at up to 350kW, an impressive feat. It charges that quickly because it has an enormous 205kWh battery pack. The Chevy Bolt, it charges at up to 50kW but only has a battery capacity of 65kW. 

Put the Chevy Bolt on the 50kW charger and it'll add about 76 percent of capacity to the battery. Put the Chevy Silverado with its 205kW battery on the same 50kW charger and it'll add about 24 percent of capacity to the battery. 

Knowing a charge rate isn't just info that makes you a good neighbor at a charging location, it's also an incredibly important piece of data. For those without at-home charging it can help EV owners determine how long they'll need to be at a charging location to add the range they'll need over the next few days.

For road-trip planning, knowing the charge rate and battery capacity of a vehicle can determine how often, for how long, and at which charging location an EV will need to stop while on the road. If your vehicle will charge above 200kW and you keep plugging into 150kW stations, you're just adding unnecessary time to your trip. 

What's confusing is that automakers are not always upfront with the charge rate number, you need to dig for it either on their site or via a trusted review site. Most automakers will state a time for charging, typically from 10 percent to 80 percent. But some will also state that number when connected to a 350kW charging station which has led some to believe that a vehicle will charge at up 350kW which isn't the case most of the time. 

For example, on its site Hyundai says "In combination with a 350 kW DC super-fast charger," the Ioniq 5 will charge from 10 percent to 80 percent in about 18 minutes. Which is incredibly quick. But the Ioniq 5 supports DC fast charging up to 235kW (which is also very quick) not up to 350kW.

While it's important to know the charge rate of your EV it's also important to note that charging rates will vary based on battery temperature, environmental temperatures, charging station hardware and software issues, and the charging curve of batteries. Once you hit 80 percent most batteries will reduce their recharging rate to protect the battery. So keep that in mind. 

Fortunately, most charging station companies are installing locations where all the stations are 350kW or above which should remove the guessing game of where to charge. Still, there are a lot of mixed charging locations out there and armed with the knowledge of how quickly your EV can charge will make everyone's experience better. 

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