4 ms·
> 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 batter
by coin 1y ago
> 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.
- sixothree 1y agoThe package says 3.85v so certainly this is a lipo.
- nwallin 1y ago> 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 1y agoYou 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 1y agoSo that's why it doesn't align with existing industry units and always requiring conversions...
- bregma 1y agoThank 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.
- lotsofpulp 1y agoDo 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 1y agoYes, 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.
- deleted 1y ago[deleted]
- lotsofpulp 1y agoThanks, I see now from: https://en.wikipedia.org/wiki/Solar_time https://en.wikipedia.org/wiki/Solar_time 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).
- numpad0 1y agoNo, 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.
- macrocosmos 1y agoWe 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 1y agoIt'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
- greesil 1y agoI prefer to use British Thermal Units (BTU) for my battery capacity.
- SV_BubbleTime 1y agoI use calories… then I can plan my meals and electronics together.
- user_7832 1y agoI 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 https://en.wikipedia.org/wiki/Calorie)
- vidarh 1y ago> 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 1y ago1 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.
- vidarh 1y agoI 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...