Comment by coder543 | Hacker News Reader

Comment by coder543 | Hacker News Reader

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"mAh" is a useless measurement that should be banned from marketing to the public, period. It does not actually represent the energy stored in the batteries, and it can easily mislead people. I also get annoyed that no one uses Ah, when "thousands of thousandths" is a really annoying way to communicate. 3200mAh -> 3.2Ah. Why do no manufacturers understand this? And why don't manufacturers just use a proper unit that measures the energy stored in the battery?

You must compare watt-hours (or use joules, if you like) for it to be meaningful. AAA voltage is 1.5V, lithium ion voltage is 3.7V or 4.2V or something, which means that each "mAh" is worth several times as much as one from a AAA battery.

The iPhone 14 Pro battery is about 12Wh. A single AAA battery has about 1.9Wh, according to google. So, 6 AAA batteries, optimistically, excluding other factors that could raise the count. Using your number of 800mAh*1.5V=1.2Wh, which would mean 10 AAA batteries.

The load characteristics also matter. Under certain load profiles those AAAs won't come even close to their rated capacity (no matter what misleading unit used). I also find the 1.9wh very optimistic, I guess you took the average AA capacity, in which case the battery would almost become bigger than the phone.

1.9 seems like a typo as 12/1.9 is 6.3, nowhere near 10. 800mAh seems to be a pretty available capacity and yields 1200mWh which tracks with the factor.

Though I think I’ve seen up to 1200.

1.9Wh was the number I saw on Google. 10 was just me not thinking clearly late at night. I updated my comment.

Load characteristics do complicate things as well, but I figured even the optimistic case involved enough batteries to dissuade anyone from this idea.

There are other non-rechargeable chemistries that are far more energy dense than AAA batteries, and those might be interesting to discuss.

Preach brother.

I guess it kinda worked when everything was 1.5V but even then it was pretty stupid, and it’s been a while.

And I feel like we’ve regressed somehow? Didn’t every smartphone use to advertise battery capacity in (m)Wh, like laptops? I feel like just a few years ago that was the prominent measure, and you’d get voltage and Ah as side-notes, e.g. the iPhone 12 wiki page states

> 3.83 V 10.78 Wh (2,815 mAh)

mAh is perfectly fine for a first-order comparison of two competing batteries, because those two batteries will only compete for a specific workload if they have the same voltage. If I need a phone with a large battery, and all phones are 3.8 volts (yes, I do mean 3.7-4.2) then comparing mAh is useful, (assuming background battery usage of the two devices is similar, which actually isn't often true, but that's a different issue).

> mAh is perfectly fine for a first-order comparison of two competing batteries

And yet it’s still dumb, because the actual energy density would let you make the exact same comparison anyway, and it would allow for easier comparison with other battery types or contexts.

> If I need a phone with a large battery, and all phones are 3.8 volts (yes, I do mean 3.7-4.2) then comparing mAh is useful

It’s not, there’s a >10% difference between the top and the bottom of the range.

Just give actual energy values, it’s strictly more useful.

Advertisers don’t care about useful. Many customers see mWh and mAh and think “that’s probably the same… and look! this one has thousands of em!”

Weirdly this doesn’t even hold, every battery is more than 1V so the Wh is always larger than the Ah. Makes no sense.

I think the mAh stays more or less constant no matter how fast you discharge the battery, but as current increases, the voltage drops so the total watt-hours is lower.

Hmmm that does make some sense, so a Wh value would either be approximate (off of the average / nominal battery voltage) or it would need to be a non-trivial integration over the battery’s voltage change?

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