What a car charger does and why you might need one
A car charger is a device that plugs into your vehicle's 12-volt power outlet (the cigarette lighter socket) or USB port and lets you charge phones, tablets, and other small electronics while you drive. It converts your car's electrical system into the right voltage and current for your device, so you can keep your battery from draining during long trips or daily commutes.
You might need one if you rely on your phone for navigation, music, or calls during driving, or if you travel frequently and want to avoid arriving with a dead battery. Some people use them as backup charging when they forget to charge devices at home.
Key Takeaways
- Car chargers plug into your 12-volt outlet or USB port and charge phones and tablets while you drive.
- The two main types are 12-volt chargers (slower, work in any car) and USB chargers (faster, require a USB port or adapter).
- Charging speed depends on the charger's wattage and your device's battery capacity — higher wattage means faster charging.
- A quality car charger costs between $15 and $50 and should have safety features like overcurrent protection.
12-volt chargers versus USB chargers
A 12-volt charger plugs directly into your car's power outlet (the round socket that used to hold cigarette lighters). It has a built-in adapter that converts 12 volts into the lower voltage your device needs. These chargers work in every car made in the last 50 years and are usually the cheapest option, but they charge more slowly — typically adding 5 to 10 percent battery per hour depending on your device.
A USB charger plugs into a USB port in your car's dashboard or center console. If your car doesn't have a USB port, you can buy an adapter that fits into the 12-volt outlet. USB chargers are faster because they deliver more power — usually 12 to 30 watts — and most phones and tablets now charge faster through USB than through older 12-volt adapters. The trade-off is that you need a USB port or an adapter, and the charger itself costs a bit more.
Many newer cars come with built-in USB ports, so you may not need to buy a charger at all. Check your car's manual or look in your dashboard and center console to see what ports you have.
How fast a car charger will charge your device
Charging speed depends on two things: the charger's wattage and your device's battery capacity. A charger's wattage tells you how much power it delivers — a 5-watt charger is slower than a 20-watt charger. Your device's battery capacity (measured in milliamp-hours, or mAh) tells you how much energy it can hold. A larger battery takes longer to charge, even with a powerful charger.
Most phone chargers deliver between 5 and 20 watts. A 5-watt charger might add 1 to 2 percent of your phone's battery per minute, while a 20-watt charger might add 3 to 4 percent per minute. Tablets have larger batteries and charge more slowly than phones, even with the same charger. If you want to charge a tablet quickly, look for a charger rated 18 watts or higher.
Your car's electrical system also matters. Older cars with worn batteries or alternators may not deliver full power to the charger, which slows charging. If your car's battery is weak, the charger may not work at all until you drive long enough for the alternator to recharge the battery.
Safety features to look for in a car charger
A good car charger has overcurrent protection, which stops the charger from sending too much power to your device if something goes wrong. This prevents your phone or tablet from overheating or being damaged. Look for chargers labeled with "smart charging" or "intelligent charging" — these terms usually mean the charger has built-in safety features.
Temperature protection is also useful. Some chargers shut off automatically if they get too hot, which can happen if you leave the charger plugged in on a sunny day. This protects both the charger and your device.
Avoid chargers with no brand name or chargers that are extremely cheap — they are more likely to lack safety features. A quality charger from a known brand costs between $15 and $50 and will last several years.
What to check before you buy
First, look at your car's ports. Does it have a 12-volt outlet, a USB port, or both? Check your car's manual or look in your dashboard, steering column, and center console. If you have a USB port, you may not need to buy anything — you can use the cable that came with your phone or tablet.
Second, think about what you want to charge. If you only charge one phone at a time, a single-port charger is fine. If you want to charge a phone and a tablet at the same time, look for a dual-port charger. Make sure the charger has enough wattage for your devices — if you are charging a tablet, get at least 18 watts total.
Third, check the cable. Some chargers come with a built-in cable, while others have a port where you plug in your own cable. Built-in cables are convenient but harder to replace if they break. Chargers with ports let you use any cable you already own.
How to use a car charger safely
Plug the charger into the outlet or USB port before you plug your device in. This prevents a power surge from damaging your device. Once the charger is in place, plug your phone or tablet in and check that it is charging — most devices show a charging icon on the screen.
Do not leave the charger plugged in when the car is off for long periods. Even when your car is parked, the charger draws a small amount of power from the battery, which can drain it over hours or days. Unplug the charger when you reach your destination.
If the charger gets very hot, unplug it and let it cool down. A warm charger is normal, but one that is too hot to touch may have a problem. Do not use the charger again until you know what caused the overheating.
Alternatives if a car charger does not work for you
If your car's battery is too weak to power a charger, or if you do not have a 12-volt outlet or USB port, you have other options. A power inverter plugs into your 12-volt outlet and converts it to standard household power (120 volts), so you can plug in a regular phone charger. Inverters are bulkier than car chargers and draw more power, but they work with any charger you already own.
Another option is to charge your device before you drive. If you know you will be in the car for a long time, charge your phone or tablet fully at home or at work. This is free and does not depend on your car's electrical system.
If you drive an electric vehicle, you may have a high-powered charging port that can charge devices much faster than a 12-volt outlet. Check your vehicle's manual to see what ports you have and what they can power.
Frequently Asked Questions
Will a car charger drain my car battery?
A car charger draws power from your battery, but only while the engine is running. The alternator (which charges the battery while the engine runs) produces more power than the charger uses, so your battery stays charged. If you leave the charger plugged in while the car is off, it will slowly drain the battery over hours or days, so unplug it when you park.
Can I use any phone charger in my car?
Not directly — a phone charger plugs into household power (120 volts), not your car's 12-volt system. You would need a power inverter to convert your car's power to household power first. A car charger is simpler because it plugs directly into your car's outlet or USB port.
What is the difference between a 1-amp and a 2-amp car charger?
Amperage (amps) measures how much current the charger delivers. A 2-amp charger delivers twice as much current as a 1-amp charger, so it charges faster. Most modern phones charge best with 2 amps or higher. Check your phone's manual to see what amperage it supports.
Is it safe to charge my phone while driving?
Yes, as long as you do not handle the phone while driving. Plug it in, place it in a holder, and leave it alone until you reach your destination. Texting, calling, or looking at the screen while driving is unsafe regardless of whether the phone is charging.
Why does my car charger stop working when the engine is off?
The 12-volt outlet in your car only has power when the engine is running (or when the ignition is in the "on" position). Once you turn off the engine, the outlet loses power. This is by design — it prevents the charger from draining your battery while you are parked.