How to Use AAA Batteries in Place of AA

Updated: Mar. 09, 2024

Knowing this hack, plus a basic understanding of battery voltage, can really help you out in a pinch.

Whether they’re powering your stud finder, laser level or TV remote, batteries are a crucial part of our everyday lives. So when I discovered this hack that turns your AAA batteries into AA batteries, it not only blew my mind, but saved me from making emergency battery runs on numerous occasions.

What is the Hack for Using AAA Batteries in Place of AA Batteries?

A while back, I came across a video on social media showing somebody’s wireless computer mouse not working because of dead AA batteries. The user then positioned a much smaller AAA battery in its place, with a small wad of aluminum foil filling the gap between the negative end of the battery and the metal connecting plate inside the mouse. As a result, the mouse worked.

I was skeptical, so I tried this hack with my TV remote, Xbox controller and camping headlamp. It worked fine in all three.

AAA battery with tin foil used instead of AA batteryEthan O'Donnell/family handyman

But Aren’t AAA Batteries Smaller and Therefore Less Powerful?

Yes. But here’s what I didn’t know: AA and AAA batteries put out the same 1.2- to 1.5-volts. That’s why the AAA battery could power the dead computer mouse.

Voltage is the difference in charge between a battery’s negative and positive terminals. Imagine a battery as a water pipe or garden hose; voltage is the pressure inside the hose. Rather than pushing water, the battery pushes electrons from one point to another.

There is a difference, however, in how long their power lasts.

Because the AA batter is larger, it has a larger output capacity. AA alkaline batteries offer a capacity of around 2,200 milliamp-hours (mHa), while AAA batteries offer about 1,000 mHa. So if powering the same device, the AA battery would last more than twice as long. If we’re talking longer lasting lithium batteries, it’s four times as long.

Why The Aluminum Foil Hack Works

Simple: Aluminum conducts electricity. The little foil wad bridged the gap between the much smaller AAA battery and the terminal inside the mouse, successfully completing the circuit.

Final Thoughts

We’re not suggesting you never need to buy AA batteries again. This is a stopgap until you can buy more batteries from the store. Just know the next time you’re on a family camping trip and your AA battery flashlight dies, you can borrow a AAA battery from another gadget, add a little aluminum foil and you’re good to go.