How we test batteries

Only the batteries that last the longest and power your devices without any problems can be rated as Best Buys.

We’ve tested a range of AA batteries and AAA batteries in the Which? test lab, using a strict range of criteria so you can be sure that the ones you buy really do last the distance in your devices. 

We analyse more than 1.5m data points in our tough tests so our reviews can answer your most crucial questions about batteries:

• How long will the batteries last in my devices?
• Will they leak and damage my devices?
• Should I buy them?

Want to know which batteries are best? Go straight to our disposable batteries reviews to find out which ones are good enough for Best Buy status. 

Or take a look at our rechargeable batteries reviews. To find out more about our testing, read on.

Which? battery life tests

Battery life tested in hours and minutes across a range of Best Buys:

How long will the batteries last in my devices?

Your alarm clock, remote control and child’s battery-powered toy need different amounts of energy, which they use at different rates. We test disposable batteries in three different conditions that mimic the devices you’re most likely to use them in – so you know which will power your devices for longest.

Our high-drain tests measure how long disposable batteries last in the most power-hungry devices, such as remote-controlled toys. Medium-drain mimics items such as lighting or games console handsets. Low-drain tests show how batteries last in devices such as clocks and clock-radios - these use a small and steady amount of power over a long period.

We time how long it takes each battery to run down to 1V (when most devices stop working) and their end voltage (when all devices stop working). The best AA disposable batteries last more than three and a half hours longer than the worst in the most power-hungry devices. They last an astonishing 13 hours longer in low-drain devices. Find out which ones we’re talking about - see our best batteries.

Of course, our tests can’t simulate every single device that uses batteries. So we also calculate the amount of energy each battery contains, taking into account all our test results. This means you can use our test results to choose the batteries that pack the most power.

Will the batteries leak and damages my devices?

If you've ever left your batteries in a gadget, then found out later they've leaked, then you'll understand why we perform a leakage test. 

At worst, a leaking battery damage your device to the extent that it no longer works, if the leaked electrolyte corrodes the contacts of the device. So that you know which batteries to watch out for if you're likely to store them in a device where they could go flat, our leakage test uncovers which batteries are most likely to leak. 

We discharge four of each disposable battery, store them, and then check each week for any signs of leakage. The image below shows batteries being put through our leakage test.

Should I buy them?

All of our tests contribute to a total test score. The higher the score, the better the battery did in our tests.

Certain assessments are more important than others and so carry different weights. We think the most important job of a battery is to power your devices for the longest, so a large proportion of our total test score is based on this. Our overall ratings ignore price and are based on:

• 35% high-drain life
• 30% energy
• 26% medium-drain life
• 9% low-drain life

Top-scoring batteries that get 73% or over earn our Best Buy recommendation. Disposable batteries that score 45% or less are highlighted as Don’t Buy batteries to avoid.

Want to find out which batteries topped our tests? Go straight to the best batteries.