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.
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.
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.
I was thinking along the lines of the ancient Sumerians arbitrarily deciding to divide 1 day into 24 hours, and 24 hours into 60 minutes, and 60 minutes into 60 seconds, and how that doesn't have anything to do with how humans came up with the concept of 1 year (the Earth rotating around the sun).
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.
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.
I see there's some use of it after having done some searches, so I'll concede it makes some minor sense as a means to disambiguate due to the Calorie/calorie confusion. Especially as "calorie" and "gram calorie" then means the same thing. This is actually the first time I can recall having seen anyone use it, though, and so for me at least it confused matters rather than clear it up...
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.
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.
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:
1 joule is 1 watt-second to be precise. So 1Wh is 3600 joules.