Using a Power Inverter in your Car, Truck, or RV

Car batteries are powerful. They have to be, after all, to keep starters starting, air conditioners blowing, and all the lights and electronics inside your car energized. We rely on our car batteries for more than just vehicle movement, though. If you’ve ever plugged your mobile phone into the car’s cigarette lighter, you’ve used the car to provide that power.

If you’ve ever wondered about the logistics of plugging in a laptop computer, video game console, or even a small refrigerator, you’re not alone. Did you know that it’s entirely possible to power these items with your vehicle’s battery?

The process is more complicated than simply plugging an item into the lighter and hoping it works, however. Because of differences in the electrical current provided by the battery and used by these items, you need a special tool to make that conversion. That tool, a power inverter, can help make this happen.

Let’s look at how power inverters work, why you need one, and how to safely connect them to keep your electronics or tools powered up and working.

What is a power inverter?

A power inverter changes direct current (DC) to alternating current (AC). Your car’s battery uses DC to supply power to your electrical components; many household electronics, by contrast, use AC. The power inverter allows you to operate these devices with power from your vehicle by turning it into current that you can use.

In addition to leveraging automotive batteries for energy, power inverters are often used for “off-grid” living; larger power inverters are hooked up to banks of batteries and solar grids to power basic appliances.

Why do I need a power inverter?

The battery in your car supplies current on one circuit, going in one direction. This is why we call it “direct current.” Alternating current, meanwhile, provides more power than what DC normally provides.

If you plan on using electronics such as DVD players, video game consoles, laptop computers, or other tools or appliances in your car, truck, or RV, a power inverter is required.

What kind of power inverter do I use?

Power inverters are available in a variety of sizes. Common variants include 1,000 watt, 3,000 watt, and 5,000 watt models. Many users choose the 3,000 watt option for the flexibility it offers. This inverter allows you to power standard small appliances. For larger needs, more wattage may be required.

Power converters can be small enough to plug into a cigarette lighter. You can also find devices that are big enough to require dedicated space in the back of your trunk until they’re needed. 

Power inverters are also available in both pure sine wave and modified sine wave options. Pure sine waves can provide better current fidelity than modified ones, but often at a premium price. Modified sine wave inverters have reduced efficiency and are often more affordable, but there are some devices—such as TVs—they may not be able to power.

How do I use a power inverter?

Depending on the model of your inverter and what you intend to run with it, using your power inverter looks different. For electrical loads up to 200 watts, you can probably plug the power inverter into the car’s cigarette lighter. Common devices powered this way include:

• Laptop computers
• Small power tools
• Most small appliances
• Small (13”) TVs

For larger energy needs—or for multiple items at once—the power inverter may need to be connected directly to your battery. If you want to power a load greater than 200 watts, the inverter should be wired directly to the battery to ensure safe operation.

Do power inverters drain car batteries?

The short answer: Yes.

The long answer, of course, is more complicated. If we assume that the battery is both fully charged and in good condition, it’s possible that a 400W power inverter can be used without starting the car for around an hour before the battery is fully discharged.

To find out just how long the battery can last with any given power inverter, you need to do a little math:

Take the wattage being used (400W) divided by the voltage of your battery (12V) to see how many amps the inverter draws. 400 watts divided by 12 volts is 33.33 amps. Inverters can only convert power at around 90% efficiency, however. The inverter is really drawing 37 amps.

Typical car batteries have a reserve capacity of about 80 minutes (80 minutes at 25 amps). If you draw 37 amps with the 400W inverter, you’ll completely discharge the battery in about 54 minutes or so: ((80 minutes x 25 amps)/37 amps = 54 minutes.)

For this reason, it’s a good idea when using a power inverter to turn the car’s engine on every 30 minutes to help maintain battery charge.

What features does my inverter need?

What you need for your inverter depends on what you plan on using it for, but some standard features can help make using your devices more convenient. Several models of power inverters are available with multiple 120V AC household outlets, useful for powering multiple devices at a time. 

Another useful feature for power inverters is a USB port. This allows you to charge your mobile phone or other devices with the power inverter.

For heavy-duty needs—such as heavy power tools or multiple pieces of equipment—look for a power converter that allows you to easily connect or clamp to your car’s battery.

Common safety features to consider when shopping for your power inverter include high-speed fans to keep the device cool, thermal protection, and surge protection. Quality-of-life upgrades, such as a low battery alarm or an LED indicator, can also help you safeguard both your battery and your devices.

Where can I find a power inverter?

If you’ve decided that using your vehicle’s battery to run electronic devices, tools, and other appliances on your next camping trip or adventure sounds convenient, the next step is finding a power inverter.
Luckily, Schumacher Electric offers a wide selection of power converting devices to meet your needs; whether you’re a contractor who needs a power inverter to provide some much-needed juice to your tools on an off-grid job site, or you’re a video game enthusiast who wants the ability to play from the passenger seat, we can help. Find the right power converter product for your budget today.