[coin]

> Watthours is more important than amp hours

I'd go a step further and say that amp hours is meaning less since voltage is not specified. The only valid battery capacity unit of measure is watt hours. While most battery packs use a single 3.7 lithium ion battery, Apple's first gen MagSafe battery pack used two internal batteries in series, throwing off everyone's amp hours only comparison.

[nwallin]

> The only valid battery capacity unit of measure is watt hours.

I would also accept Joules. But yes, the unit should be a unit of energy.

[beAbU]

You are probably making a joke, but just in case and for those that don't know, a joule _is_ a watt hour.

1 joule is 1 watt-second to be precise. So 1Wh is 3600 joules.

[numpad0]

So that's why it doesn't align with existing industry units and always requiring conversions...

[bregma]

Thank goodness SI units are power-of-ten based so converting between watt hours and joules is just a matter of moving the decimal place. Oh, and throwing in an ancient Sumerian constant approximating the number of Earth rotations as it revolves around the sun once.

[numpad0]

No, Watt-second-hour = 3.6 kJ, so J to Wh is moving the decimal place couple steps AND dividing by 3.6. The actual units used in circuit designs is mAh, so the decimal has to be moved for another time then divided by 3.7[V] again. That's too much for a smooth-brained man like I am.

[lotsofpulp]

Do seconds have anything to do with the Earth rotating around the sun? I thought a second just has to do with the Earth’s rotation on its axis.

Also, I wonder how usable a unit of time that was not based on a day would be, since so much of our life revolves around that cycle.

[tnlnbn]

Yes, seconds are related to the Earth rotating around the sun. Simplifying slightly, the normal definition of a day relates to how long for Earth to rotate on its axis until the same spot on the Earth points at the sun again.

Compare Mean solar day vs Stellar day vs Sideral day - the difference is less than 5 minutes or so.

[greesil]

I prefer to use British Thermal Units (BTU) for my battery capacity.

[SV_BubbleTime]

I use calories… then I can plan my meals and electronics together.

[user_7832]

I know it's a matter of taste but personally I prefer to use the Calorie instead of the calorie ;)

(Context: 1 Calorie = 1 kilocalorie = 1000 (gram) calories; https://en.wikipedia.org/wiki/Calorie)

[vidarh]

> 1000 (gram) calories

The "(gram)" make no sense here. We commonly use "kilo" as shorthand for kilogram", but kilo is just a prefix indicating 1000 and never indicates "kilogram" when given as a prefix to another unit, and so there's no implied/left out "gram" in 1 kilocalorie.

[spuz]

1 kilogram Calorie is the amount of energy needed to raise the temperature of one kilogram of water by 1 degree. 1 gram calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 degree.

[eesmith]

Today I learned there are multiple BTU definitions. https://en.wikipedia.org/wiki/British_thermal_unit lists Thermochemical, 59 °F, 60 °F, 39 °F, and International Steam Table.

Though as the difference is at most 0.5%, it's probably won't affect your battery buying experience. :)

Measuring by TNT equivalent is more standardized. "This battery stores 50 grams of TNT."

Ummm, on second thought, maybe don't use that term at the airport, .. or in secure areas, ... or near the police, ... or in public, ... or on social media or anything else tapped by the NSA or other authorities.

[macrocosmos]

We could also talk about lb•AU (pound Astronomical Units), but generally it's best to stick to what's standard so readers don't need to do conversions. Watt hours is great.

[fy20]

It's not terrible... The iPhone 17 has a battery capacity of 63 nano lb·AU. Around 16 million would equal 1 lb·AU.

Another fun one would be milli hundredweight leauge (mcwt·lg). Both hundredweight and league have multiple accepted definitions to make it more "fun". But the range maps quite nicely to everyday things:

AA battery - Around 5 mcwt·lg

Phone battery - Around 20 mcwt·lg

Laptop battery - Around 200 mcwt·lg

Car 12v battery - Around 1,000 mcwt·lg

EV battery - Around 100,000 mcwt·lg

[sixothree]

The package says 3.85v so certainly this is a lipo.