Will Charging Your Phone In Your Car Drain Its Battery?

Modern vehicles are fitted with several ports where you can plug in a phone charger. There’s the auxiliary power outlet or cigarette lighter. Most modern vehicles also have several USB ports on the dashboard and center console. Some vehicles even have wireless charging. Using these ports to charge or power devices draws power from the vehicle’s battery. At a certain point, the vehicle’s battery can run out of juice, which can cause a wide range of issues.

Can the vehicle power or charge all the devices plugged into these ports? Will it discharge your vehicle’s battery? We’ll answer these questions in this article.

Does charging your phone in the car drain the battery? Yes, but you can freely charge your phone and electronics as long as your vehicle’s engine is turned on. Your vehicle’s alternator can continuously replenish your vehicle’s battery as your phone and vehicle draw power. So, as long as your vehicle is moving or on idle, your engine should be turning the alternator and creating enough power.

Can You Charge Your Phone With the Engine Turned Off?

You can still charge devices from your vehicle’s ports as long as the vehicle’s electronics are turned on. Most cars have an accessory socket with power even when the engine is turned off. Some cars require the key to be turned to the “on” position. However, since the engine is turned off, the alternator won’t be able to replenish the battery.

Does charging your phone with the engine turned off draw too much power and leave you with a flat battery? Theoretically, it’s possible. However, it’s highly unlikely because charging a phone only uses a small amount of power from a car’s battery.

How Long Can You Charge Your Phone With the Engine Turned Off?

Mobile phone battery capacity is rated in milliampere hours (mAh). Modern phones tend to have around 3,300 to 4,400 mAh, depending on their model. Meanwhile, vehicle batteries are rated in ampere-hours (Ah), where 1 Ah is equivalent to 1,000 mAh. Vehicle batteries can typically store around 50 to 70 Ah, depending on the battery’s size. Assuming that the vehicle’s battery is fully charged, it can charge 15 to 21 phones before running out of power. If you’re just charging one phone, you can probably fully charge it without issues.

However, this assumes that the vehicle’s battery hasn’t deteriorated or is nearing the end of its lifespan. As batteries age, the amount of power that they hold decreases. If your battery is nearing the end of its lifespan, then charging your phone from your vehicle’s battery can be a little risky.

The next time you wonder “Can I charge my phone in my car with the engine off?” first ask yourself if your vehicle’s battery has recently shown signs of failure. If you’ve recently had to jumpstart your vehicle because the battery died, then you should reconsider charging your phone with the engine turned off. You should also reconsider charging your phone with the engine off if you’ve had trouble starting the engine, as it could mean that the battery isn’t providing enough voltage to the starter anymore.

At the end of the day, if you’re still worried about charging your phone, just know that vehicle manufacturers have given vehicles auxiliary power outlets, USB plugs, and wireless chargers for a reason.