Why is no capacity indication on regular batteries?

On every rechargeable battery there is an indication how big the capacity is (for example 2500 mAh). Why is this not the case with normal (nonrechargeable) batteries ? I tried to google the question but found no answer.

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Perhaps because capacity is very dependent on discharge rate and temperature - I don't know if this is more so than for other chemistries. –  RedGrittyBrick Jan 12 '14 at 11:13
Alkaline batteries have a significant internal resistance compared to rechargeable so the more demanding the load (in current) the more energy is going to be wasted as heat in the battery itself. –  alexan_e Jan 12 '14 at 12:07
Some non-rechargeable batteries DO have such indications - not on the cell, but in datasheets where more info such as discharge rates can be given. For example, farnell.com/datasheets/62309.pdf –  Brian Drummond Jan 12 '14 at 12:13
Sounds logical, why dont you post this as answer ? –  user2664856 Jan 12 '14 at 12:13
@alexan_e: the internal resistance itself does not affect the mAh rating! (But it is possible that the heating or other current-dependent effects cause degradation.) –  Wouter van Ooijen Jan 12 '14 at 19:35

The answer is: marketing. Some number, like "1800 mAh", doesn't really mean anything, anyway. At what temperature? At what voltage is the battery considered "dead"? At what current? The charge you can get from any type of battery really depends on these factors, and how far dead you are willing to run it.

All the major alkaline battery manufacturers supply datasheets that specify the capacity of their batteries more completely. This is the place to get capacity information, not the product label.

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"at what voltage is the battery considered dead": for rechargeables the discharge curve often falls of steeply, or discharge beyond a certain point will damage the cell. Hence there is little discussion about the end voltage, so a mAh rating makes sense. Non-rechareables often have a flatter discharge curve, and the condition of the cell after discharge is not an issue, so there is no single mAh rating. –  Wouter van Ooijen Jan 12 '14 at 19:34

As the commenters before pointed out, the capacity in alkaline batteries depends on the load. You can still find capacity information in the datasheet of the manufacturer, e.g. for a Energizer AA battery: data.energizer.com/PDFs/E91.pdf

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Some brands actually mention their capacity on the packaging - for example, Carrefour's AA, AAA and 9 volt ones. And they aren't far away from the truth.

Also, different brands of alkaline batteries are not so different internally, as they all use a very similar chemistry, so the capacities are accordingly quite similar for a broad spectrum of brands, as you can see here. There are models which are more suited to light loads (i.e. TV remote controls) and are optimized to last long, whereas others are designed for high-current applications. As other people mentioned, capacity depends on drain current, and instead of printing a table of capacity vs current, it's easier to market cells as "high power", "long life", "heavy duty", etc.

The serious technical data is in the datasheets.

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Realistically, the answer is because the alkaline battery marketing people would rather compete on brand name than rated capacity. They prefer traditional marketing tactics such as who spends more money on advertising, does deals with more distributors and retailers, leading to consumer perception that market leadership equates to technical leadership. In the U.S. consumer market, Duracell/Energizer is like Coke/Pepsi, and everyone else is like the grocery store house brand. The chart from anrieff's link shows that neither of them makes the highest-capacity cells (in that test), Varta does, yet they command around 30% market share each.

From a November 2013 article in Advertising Age: "We're just sticking to a very simple strategy, which is building strong retailer partnerships, innovation and brand building," said Duracell Marketing Director Jeff Jarrett. [...] Duracell has shied from performance comparisons, because consumers are tired of the "longevity arms race" in ads over the prior three decades.
What it means for the consumer is that the smart shopper should pick a brand which is within the ballpark of the technical leaders by capacity, but costs much less per cell, and just live with changing batteries a little more often. In practice this plan doesn't constitute a big threat to the dominant players, because the lowest prices may be loss leaders meant to attract visitors to particular store chains that most people don't ordinarily visit on a regular basis. Ikea seems a good example - excellent price per energy, but not a store people visit often once they've got the furniture and housewares they need, so it's still more convenient to toss some Energizer in the cart at the grocery store. For those running through an expensive amount of batteries it might be cheaper in the long run to switch to NiMH rechargeable e.g. Eneloop. Or run from wall power if possible, which costs around $0.00012 per Watt-hour, compared to$0.20 for AA alkaline, a 99.9% cost savings.