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Whether you drive a vehicle from Toyota, Honda, Chevrolet, or BMW, we’re willing to bet the car, truck, or van you own has at least one USB port. It’s even more likely that a new vehicle will have multiple USB ports, with many models offering a mix of USB-A and USB-C connections, or primarily the latter.
Your car’s USB ports can do more than you think, but one of their main functions is charging and powering mobile devices like smartphones and dash cams. With that in mind, you might be wondering if leaving a USB device plugged in all the time will result in a dead car battery. For most modern vehicles, you should have nothing to worry about, and that’s thanks to a feature known as Retained Accessory Power (RAP) on some vehicles, or simply “delayed accessory power” on others.
The idea behind RAP is to allow certain vehicular hardware to stay powered once the ignition has been switched off, and usually for several minutes. Once the appropriate amount of time has elapsed, your vehicle’s RAP system should then cut power to USB ports, car infotainment interfaces, and other electronic components. But again, RAP is just one example — plenty of vehicles cut power to the USB ports automatically after you shut the car off, even if the manual doesn’t call it RAP.
Your vehicle’s alternator and battery are a dream team you don’t want to disturb
Make and model preferences aside, most modern vehicles are equipped with numerous electrical components, all of which tie back to the vehicle’s battery. This includes the one or several USB ports built into your daily drive, as well as your electric sunroof’s motor, your radiator fan, and even the heat generated by your interior vents.
Fortunately, when you’re driving, or your vehicle is idling, the alternator is constantly working to restore power to the battery. So it’s when your car is parked and turned off that a drained battery might become a concern. If you’re unsure whether your vehicle is equipped with RAP technology or something similar, you can always check the owner’s manual. But if you just want to err on the side of caution, you can unplug any USB-connected devices before exiting your vehicle for a long period of time.
If you’re in a position where you have a bunch of cool gadgets using up your car’s USB ports, you can always invest in a 12-volt USB adapter to upgrade your car’s old-style power outlet. Before you buy one, though, you should check to see if your vehicle’s 12-volt plugs are only powered when driving (safe to keep USB devices plugged in) or if they’re battery-operated and receive constant power (not safe to keep USB devices plugged in).
