Engadget Guide Explains How to Test a CR2032 Battery Before Replacing a Device

According to Engadget, the first step is to inspect the battery itself. Crusty residue, rust-colored patches, swelling or leakage mean the cell should be replaced rather than tested. The device contacts should also be checked, because corrosion there can cause problems even when the battery is good.

For a multimeter test, Engadget says to set a digital multimeter to DC voltage, plug the black lead into COM and the red lead into the V or VΩ port, and select a range above 3V, typically 20V, if the meter does not choose automatically. The battery should be held by its edges over a nonconductive surface. The red probe touches the broad face marked with a plus sign, and the black probe touches the center of the smaller negative face underneath. The probe tips should not touch each other or bridge the battery terminals. A negative reading means the probes are reversed.

Engadget reports that a fresh CR2032 typically reads around 3V, while a reading closer to 2.5V is a good reason to use a replacement. But the guide cautions that a 3V reading is not a complete picture of battery health. A multimeter draws almost no current, so a battery can look fine on the display and still struggle when a key fob or tracker needs power. There is no single pass-or-fail reading for every device, and Engadget says a fresh CR2032 should be tried if a device keeps acting up.

For people without a multimeter, Engadget lists a dedicated coin-cell tester, with some costing around $10, though certain models only measure voltage rather than performance under load. Basic multimeters can cost less than $20 and are useful for other batteries or low-voltage electronics, but buying either just to diagnose one suspect $3 battery is a harder sell, the guide says. It also describes an LED trick: a small red or yellow LED generally needs less voltage than a blue or white one, and touching its longer leg to the positive side and shorter leg to the negative side will light it if the battery can supply some current. That does not show how much life is left, and an LED that stays dark does not necessarily mean the battery is dead.

AirTag owners can check Find My before opening anything, Engadget says. Selecting Items in the app and tapping the AirTag will show a “Low Battery” message or a depleted battery icon if replacement is needed. Some CR2032 batteries have bitterant coatings that may prevent proper contact even when new. Apple recommends packaging marked “Compatible with Apple AirTag” when replacing an AirTag battery and says an AirTag battery lasts more than a year, while Samsung rates the SmartTag2 for up to 500 days in normal mode.

Engadget also notes safety steps: after removing a CR2032, keep it out of children’s reach and tape its terminals before taking it to a battery collection facility. If one is swallowed, emergency medical care should be sought immediately, because serious internal injuries can occur in as little as two hours.

Editor's Summary

Engadget’s guide says a CR2032 can be checked visually and with a multimeter, but voltage alone may not reflect performance under load. It also points AirTag and SmartTag2 users to app warnings and replacement guidance, while stressing safe disposal.