Ask Dr. Science: Replace all batteries at the same time?
June 18th, 2010 at 11:59 am ET
Household battery packaging always carries a scary warning imploring you to REPLACE ALL BATTERIES AT THE SAME TIME. Is this really important, or is it a fiendish plot to get you to buy more batteries?
After exhaustive research, I’ve concluded that it probably doesn’t matter in normal household use — the risk of truly negative consequences from mismatched batteries (e.g., your Apple MagicMouse explodes) is vanishingly low, and the incremental energy savings probably isn’t noticeable. (Really, if you asked me “how long do your mouse batteries last?” my guess would probably be wildly inaccurate.)
However, I have no practical way to know the “residual voltage” left in each of the batteries in a device that’s stopped working. And batteries cost like 50 cents each! So, Duracell, you’ve won this one by default, it seems…
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Rich Mintz blogs on online fundraising and social media, American history and culture, bicycling and urbanism, food, technology, and other topics. Professionally, he's an expert in fundraising, constituency development, and social media for nonprofits, cultural organizations, cause-related marketers, and corporations. He is based in New York, where he serves as Vice President, Strategy, for 
