General

How to top up your EV’s battery

How to top up your EV's battery

Electric vehicle (EV) drivers are usually well aware of their remaining range before they need to recharge. In fact, EV drivers are so familiar with their cars that AAA canceled the on-road charging assistance trial service after five years due to a lack of demand. In addition, many EV drivers plan their route based on the location of a convenient public charging station, where they can fully charge their car’s battery and do a number of other things.

But what if you just need a few extra miles of range to get to your destination? Or maybe you’re having a few minutes of downtime and wondering if it’s worth “recharging” your car battery from a public charger. If you find yourself in this situation, here’s what to expect from a short-lived public charging session.

When you only need a few miles

If you’re driving home and realize your EV’s battery is low (similar to being surprised by the “low fuel” warning light in a gas-powered vehicle), you may need to visit a public charger to make sure that you come home.

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

Given all the variables, it’s hard to know exactly how long it will take to add, say, 25 miles to the battery. The Department of Transportation estimates that an EV will add 10 to 20 miles for every hour it’s plugged into a Level 2 charger. Older EVs and those with slower chargers on board will get closer to 10 miles in an hour at a slow station , but will do better on 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 faster charging speeds available at some stations. These EVs still accept the charge, just at a slower pace. The MX-30, for example, adds the same 22 miles per hour even when plugged into a 22 kW Level 2 station. On the other hand, the high-tech Porsche Taycan works like the MX-30 at slower chargers (11 mph at 3.6 kW, 20 mph at 7 kW), but outperforms the Mazda at a 22 kW Level 2 add charger by 32 miles in one hour. Many charging network operators offer kW ratings in their apps, making it easier to decide where to go when you’re short on time.

As the name implies, DC fast chargers offer shorter waiting 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 deliver any compatible EV with a range of 10-20 miles in just a few minutes, regardless of the station’s kW rating.

If you only have a few minutes

For example, if you have 15 minutes on a public charger, a level 2 plug won’t help you much. 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 want to look for a DC fast charger.

DC fast chargers can quickly charge an EV battery to 80 percent of its total capacity in about 30 minutes. The more powerful the charging station and the more capable your EV’s built-in charger, the less time it will take. But if you can only sit on a DC fast charger for a few minutes, the station’s kW rating can make a difference if your EV can accept the higher rates.

For example, the MX-30 offers DC fast charging and adds approximately 60 miles of range in 30 minutes at a 50 kW station. It offers the same extra range, even at a 150 kW station, due to limited charging options. The Taycan, on the other hand, is capable of higher kW charging, adding about 70 miles in 30 minutes at a 50 kW station, but over 200 miles in the same half hour at a 150 kW station.

Overview

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 journeys. But if you haven’t charged your car’s battery all week or if you’ve driven more than expected, you can add a few miles of range, just like you would in a petrol car. Depending on the charging infrastructure in your area and the EV you drive, this could take anywhere from a few minutes to an hour or two.

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