How to Top Off Your EV's Battery

Sebastian Blanco | Sep 27, 2022

Drivers of electric vehicles (EVs) are usually well aware of their remaining range before needing to recharge. In fact, EV drivers are so in tune with their cars that AAA canceled its trial roadside charging assistance service after five years due to a lack of demand. Furthermore, many EV drivers plan their route based on the location of a convenient public charging station, where they can fully recharge their car's battery while accomplishing a number of other things.

How to Top Off Your EV's Battery

But what if you just need a few additional miles of range to make it to your destination? Or, perhaps you have a few minutes of downtime and wonder if it's worth it to "top off" your car's battery at a public charger. If you find yourself in this situation, here's what you can expect from a short-term public charging session.

When You Only Need a Few Miles

If you are driving home and realize your EV's battery is low (similar to being caught by surprise by the "low fuel" warning light in a gas-powered vehicle), you might need to visit a public charger to ensure you make it home.

There are two main categories of public charging: Level 2 and DC fast charging. The slower Level 2 chargers operate between approximately 3-20 kilowatts (kW), with a higher number providing a shorter charge time. Separately, the onboard charger in your car, also expressed in kW ratings, will affect your charge time.

Given all the variables, it's difficult to know precisely how long it will take to add, for example, 25 miles to the battery. The Department of Transportation estimates that an EV will add 10 to 20 miles for each hour it's connected to a Level 2 charger. Older EVs and those with slower onboard chargers will get closer to 10 miles in an hour on a slow station but will do better at a faster station. The Mazda MX-30, for example, adds about 10 miles per hour when plugged into a 3.6-kW station but 22 miles on a 7-kW station.

Not all EVs can take advantage of the higher charging speeds available at some stations. These EVs will still accept the charge, just at a slower rate. The MX-30, for example, adds the same 22 miles in an hour even when plugged into a 22-kW Level 2 station. On the other hand, the higher-tech Porsche Taycan operates like the MX-30 at slower chargers (11 miles/hour at 3.6 kW, 20 miles/hour at 7 kW) but outperforms the Mazda at a 22-kW Level 2 charger by adding 32 miles in an hour. Many charging network operators offer kW ratings in their apps, making it easier to decide where to go if you have limited time.

As the name implies, DC fast chargers provide shorter wait times. The slowest DC fast charger operates at 50 kW, while the fastest stations today operate at 350 kW, with higher rates planned. The good news is that any DC fast charger will provide any compatible EV with 10-20 miles of range in just a few minutes, no matter the kW rating of the station.

When You Only Have a Few Minutes

If you have, say, 15 minutes to spend at a public charger, a Level 2 plug will not provide you with much assistance. Level 2 chargers add 10-20 miles in an hour, so a 15-minute session will likely add three to five miles. Sometimes, that's enough. Other times, you'll want to seek a DC fast charger.

DC fast chargers can quickly charge an EV battery to 80 percent of its total capacity in around 30 minutes. The more powerful the charging station and the more capable your EV's onboard charger setup, the less time this will take. But, if you're only able to sit at a DC fast charger for a few minutes, then the station's kW rating can make a difference if your EV can accept the higher rates.

The MX-30, for example, offers DC fast charging and will add around 60 miles of range in 30 minutes at a 50-kW station. It provides the same added range even at a 150-kW station due to its limited charging capabilities. The Taycan, on the other hand, can accommodate higher-kW charging and adds around 70 miles in 30 minutes at a 50-kW station but more than 200 miles in the same half-hour at a 150-kW station.

Summary

Most EV drivers in the United States, especially those who can charge their vehicle at home, should have more than enough range for their daily travels. But if you haven't charged your car's battery all week or happened to drive more than expected, you can add a few miles of travel range just as you would in a gas car. Depending on your area's charging infrastructure and the EV you drive, this could take anywhere from a few minutes to an hour or two.

Check out our Shopping Guides section if you'd like to learn more about EVs.

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