If you’ve ever bought rechargeable batteries, you’ve probably noticed that some have a number followed by “mAh” and others have a number followed by “mWh.” One reader, Tony Brunswick, noticed this with his new EBL AA batteries, which said 3,500mWh, while his old Duracell batteries said 2,500mAh. He was confused and worried that he had been scammed because the mWh number was larger.
I can tell you that you haven’t been scammed, but the marketing around battery capacities can definitely be confusing, and we’re sure some companies use this to their advantage. A mAh figure is a measure of electric charge, or how much current a battery can supply over time. A mWh figure, on the other hand, is a measure of energy, which takes voltage into account. This is where the marketing trickery comes in, as it allows companies to make their batteries look more powerful than they are.
What Are the Real Numbers?
The old Duracell batteries are probably nickel–metal hydride (NiMH) and are rated at around 1.2V. If you multiply their 2,500mAh by 1.2V, you get a figure of 3,000mWh. The new EBL batteries are lithium-ion (li-ion), which typically run at a higher voltage internally. Their built-in electronics regulate this down to a constant 1.5V output. If you convert their 3,500mWh back into mAh — by dividing by 1.5V — you get a figure of around 2,333mAh.
So, despite the larger number on the side of the batteries, the new USB-C rechargeables actually store less charge overall than the old Duracell ones. The new li-ion batteries also have to power a tiny onboard controller and voltage regulator, which drain a little energy themselves, so it’s no surprise they’ve left you feeling short-changed.
What About Your DAB Radio?
This same problem affects DAB radios. One reader noticed that the batteries in his new DAB radio drained much faster than in his old analogue radio. This is because a modern DAB radio has a small computer processor that decodes the digital signal, and this draws a continuous amount of energy. So, even though his new radio was more modern, it was less efficient with its battery usage.
- What’s the difference between mWh and mAh on batteries? Computeractive – Issue 715, 30 July–12 August 2025
- Why my DAB radio’s batteries drain so fast? Computeractive – Issue 715, 30 July–12 August 2025
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