I have a drawer full of spare AA and AAA batteries. Some are fresh, some are from remote controls that died last winter, some I found in a toy. Before tossing them or putting them to use, I check the voltage with a multimeter. It takes thirty seconds and saves you from guessing.

What you need

A cheap multimeter is all you need. Any digital one will do — I’ve used the same £8 model from Amazon for years. The probes should be intact and the battery in the multimeter itself should have charge (if it beeps when you turn it on, you’re good).

The steps

Turn the dial to the DC voltage setting. On most multimeters this is marked with a V and a straight line or dashed line beneath it. Pick a range higher than 1.5V — the “20” setting is perfect, or “200” if that’s what your meter offers. You’re measuring direct current, not alternating current, so make sure you’re in the DC section.

Plug the black probe into the COM port and the red probe into the VΩmA port. These are the standard positions for voltage measurements. If your multimeter has a separate 10A port, leave it alone — you’re not measuring current here.

Touch the black probe to the flat negative end of the battery and the red probe to the raised positive end. You don’t need special technique. Just press the tips against the terminals and hold them there for a second until the reading stabilises. The multimeter will display a number — that’s your voltage.

What the numbers mean

A brand new alkaline AA or AAA typically reads between 1.5V and 1.6V. As the battery discharges, the voltage drops. Here’s a rough guide:

  • 1.5V to 1.6V — Full charge, good to go
  • 1.4V to 1.5V — Still useful, probably 60-70% capacity remaining
  • 1.2V to 1.4V — Partially drained, might work in low-drain devices like clocks or remotes
  • Below 1.2V — Pretty much dead for most purposes. Recycle it.

These numbers shift depending on the chemistry. Lithium primaries sit higher, around 1.8V when fresh. Rechargeables (NiMH) start at about 1.2V and drop from there, so a “dead” reading on a rechargeable might just mean it needs charging.

A note on load testing

Voltage under no load isn’t the whole story. A battery might read 1.3V and look fine, then sag to zero the moment you put it in a device that draws current. If you want to know whether a battery can actually deliver power, you need a load test — something that draws current while you measure the voltage.

A simple version is to connect a small resistor (a 10-ohm power resistor works) across the battery and measure the voltage while the load is applied. If it holds steady, the battery has life left. If it drops significantly, it’s spent.

But for most household purposes — checking whether a battery is worth putting in a remote or clock — the no-load voltage test is good enough.

Where to put dead batteries

Don’t bin them. Most supermarkets and hardware stores have battery recycling bins, and many electronics shops will take them too. Lithium and alkaline batteries can leak if crushed in a landfill, so it’s worth the extra step.