You might be lactose intolerant, in which case taking lactase enzyme pills immediately before eating may relieve your discomfort.

Sorry, I basically combined two separate thoughts in a weird way. First, I meant that the raw battery cells themselves are usually rated in mAh on their datasheets, so manufacturers simply kept using that unit on their marketing material. Second, I meant that datasheets usually use mAh because it is a more appropriate unit than Ah for comparing cells of that approximate size. This is somewhat common in engineering documents - you will often see measurements written as 20.0mm instead of 2.0cm (usually because it is more consistent with the rest of the documentation). In this case it’s because many of the Li-Ion cells used in phones will have their charge/discharge ratings in mA, so it makes sense to have the capacities in the corresponding mAh.

But I do agree, on marketing material it makes much more sense to just write the capacity in Ah (or better, Wh). Using mAh just because it’s a bigger number is plain silly.

Batteries often have a rating like 3250mAh, which is arguably clearer than 3.25Ah, especially on a datasheet.

That would be ideal, but I think at this point there’s just too much marketing momentum using mAh, and switching to mWh would be too confusing to consumers. But yeah, I agree, mWh is definitely the most appropriate unit to use.

The vast majority of cell phones use a single-cell Li-Ion battery, so their capacities can be directly compared using mAh. Laptops almost always contain multi-cell Li-Ion batteries, so their capacity cannot be directly compared using mAh (e.g. a 4S battery rated for 2500mAh has more energy than a 3S battery rated for 3000mAh).

So why don’t we use Wh for phones too? Simply because manufacturers would rather advertise a battery size of five thousand mAh (wow, so much capacity!) instead of 19 Wh.

The same issue happens with portable USB battery packs - they’re all advertised in mAh even though they use a wide variety of chemistries and cell configurations internally. What manufacturers do is take the total Wh of the pack and convert it back to the equivalent mAh of a single-cell Li-Ion. It’s annoying, and I really wish they would just use Wh directly.