should you get a onboard USB charger?

Even if your car has a USB port designed to sync your smartphone with the car’s entertainment system, and even if that port can charge your phone, spending $20 or so for a dedicated two-port charger can be worth it. That’s because the built-in USB ports in most cars put out only 5 watts, which isn’t enough to charge a tablet or even newer smartphones at full speed. If you’re running an app such as Google Maps or Waze, for example, your car’s USB port may not charge your phone faster than your phone uses power, so you can end up at your destination with the same battery level on your phone as when you got into the car. Good USB-A chargers can charge more than twice as fast (12 watts), and the latest USB-C chargers can charge modern smartphones at 18 to 20 watts as long as you use a cable that plugs into the smaller port instead of the USB-A cable that probably came with your device. (These are our favorite cables for iPhones.) Even if your car’s USB port does offer higher-speed charging, most cars have only one port. All of our picks let you charge two or more devices on a single accessory outlet—something your family and friends will appreciate. However, if you recently bought a multiport USB charger that provides at least 2 amps from each of its ports (look for the “output” listing in the small print on the body of the charger), you have less reason to upgrade. Although you’d be able to charge some devices slightly faster with our top picks, the difference wouldn’t be big enough to be worth spending more money on a new model right now.