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Comment by ni-hil | Hacker News Reader

1460 mAh

To note, that it's 7.62V (i.e., 2S), so it's equivalent to most ~3000mAh packs. Still not great for the money, but not as bad as it sounds.

Why did the mobile industry decide to use mAh instead of Wh.

I think that's just the battery industry. Whenever I shop for batteries for robotics or RC vehicles they're in mAh too.

Maybe it's slightly more convenient because the same value applies no matter how many cells are in the battery pack. So it helps distinguish the packs by electrical current output capacity which we can't get from a power value because power combines two different measures.

mAh doesn't change as you add cells to the battery pack? i'm pretty sure that's not correct.

This depends on whether they're wired in series or in parallel.

Wired in series, mAh won't change, wired in parallel, it's additive.

Most commonly RC battery packs are referred to as "1S, 2S, 3S," etc. indicating how many single cells there are in the pack wired in series. Those are also individually rechargeable via a low-current charging cable.

Yep. I'm very familiar with these from quadcopters.

The charging cable is usually called a "balance plug", because it distributes power equally to all cells instead of shoving it all through all of them in series.

My e-bike’s battery on the other hand is in Wh.

laptops are always Wh in my experience.

Mobile Industry standardise on 3.8V, so you have two number to present to consumers, Wh or mah. Since Wh is a smaller number, marketing decided to use mah. Once that got traction, others that were previously using Wh had to follow. And now we end up having billions of consumers using mah as a unit and when they use it defaulting to 3.8V.

It is all too late now. Sigh.

Yeah, it doesn't get worse than rock bottom.

5000mAh compact is around $20, 10,000mAh $40 for good devices.

You're not really comparing features to features if you're comparing to a boring 5000mAh brick with wired charging.

Closest I can find is probably the Anker Qi magnetic brick: https://www.amazon.com/Anker-Magnetic-Wireless-Portable-Powe...

5000mAh, only 5W Qi charging, and $45.

Again, not defending the Apple tax here, but it's not as far fetched as it sounds.

Only 5W? What makes Apple's 5W better (no, it's not 15W when portable)?

But yeah, OK, you can attach it with magnets to the back, that's worth double the cost. Oh wait, make that triple, since you need the case.

I better stop now, shitting on Apple was a favorite pasttime of mine.

I mean, as someone looking to manufacture and sell a premium product, I'm pretty happy with it, people will pay anything for imaginary benefits.

I missed that it doesn't support 15W charging when portable. That's erodes quite a bit of the benefits then. No reason you need the magsafe case, as far as I can tell though.

Also, the Anker device does have magnets. Looks like they operate just like the magsafe.

> You're not really comparing features to features if you're comparing to a boring 5000mAh brick with wired charging.

So wired charging is boring and magnetically attached is exciting?

You know, this is not like AirPods, which are completely disconnected from the phone. It's a lump attached on your phone that you may also unintentionally disconnect and drop on the floor while taking videos of something.

I'm way more "excited" by the cable, especially given the price (you can find pretty good 5000 mAh bricks for as little as $12).

"mAh" are useless here without voltage. Its like using 50KM/hr as the towing capacity of a truck.

It's actually very useful. Ah is the best way to compare battery capacity.

I think the idea is that watt-hours (Wh) serves the same purpose and doesn't miss information about capacity if voltage is omitted. Technically though the units in watt hours should cancel out to be Joules which may be the best unit.

Are amp hours in some way better due to the varying voltage across the charge profile of a draining battery perhaps?

It's mostly because the voltage is assumed to be constant across the discharge profile (even if it isn't), and Ah is taken to the point that you can safely discharge the battery to. So you compare two batteries with the same voltage on their Ah, and systems in terms of Wh (and then the voltages are irrelevant).

One problem here is that what looks like a battery on the outside is often a system under the hood, so the output voltage is not necessarily the voltage at which the battery operates due to for instance DC-DC convertors and other electronics embedded in the battery housing.

I'd argue that the undecomposed watt-hour is in fact the superior unit for batteries.

Because what I want to know about a battery is exactly how many hours I can use it at a given wattage. The voltage is determined by application, and the only amp-related stat I'm interested in is maximum current, which is more useful to me in watts anyway.

So a 50 Wh battery which I'm going to draw at 10 watts? five hours of use time. 20 watts? 2.5, and I can do this in my head all day. Joules are less convenient because going from seconds to hours is too annoying to do as mental maths.

It's only useful if you know the voltage of the battery, so that you can calculate watt-hours, or if you at least know that two batteries you're comparing are the same voltage so you're comparing like to like. It's not useful if you're comparing batteries of different voltages unless you're adjusting for voltage in which case you want to use Wh anyway, which is why using Wh here is more useful.

It’s only useful if the batteries have the same voltage. When, as here, they don’t, you have to do some arithmetic to compare the capacities.

So it’s actually probably the worst way to compare battery capacity.

Damn, talk about reading the fine print.

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