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I think amp-hours are confusing and I wish they just gave us battery life figures in joules
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this post was submitted on 03 Apr 2026
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Unpopular Opinion
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A watt is one joule per second. So if a phone consumes 100 watts, and its battery has 1000 Joules, it'll run for ten seconds. If its battery has 8 megajoules (which is as much as an average person eats in a day), it'll run for eight thousand seconds. Which is about 2 hours. It's easy and simple.
I understand watts. I don't really understand amps. I know how many watts My PC draws because I installed the power supply Myself. I don't know how many amps it draws. I don't know how many amps My phone draws, or My wireless mouse, or My body.
My phone's battery lasts longer when I turn the screen brightness down. Does that mean the screen is drawing a variable number of amps depending on the brightness? That's confusing! I don't really understand what an amp is, so I can't visualise that. I can understand the fact that a dark screen draws less watts easy, because watts are just energy per second.
You know what it's rated for, but actual usage varies constantly. Open up your gpu overlay and it will show you the biggest users (aka your cpu and gpu).
You can install an app right now and see your phone's battery draw in mA so you don't even have to convert anything.
Then why joules?
Watthours is another already fairly common unit.
1Wh lasts for one hour at one watt. Half and hour at two watts. And so on.
Amps are directly related. You can get the amps from the wattage, by dividing the watt with the voltage being run.
Watthours are stupid. You're taking the SI unit of energy, the joule, dividing it by time to get watts, and then multiplying it by a different unit of time to get energy at a different conversion rate. It's ludicrous! I have a philosophical opposition to such confusing units.
Or, think of it as just adding time to watts.
If a thing uses 100 watts. Then in one hour, it used 100Wh.
It's literally the simplest unit for this.
That's not addition, it's multiplication.
...
Adding. As in combining. Introudcing. Attaching. Affixing.
Not math.
Well, you gonna love freedom units
Actually I think of amp-hours as an imperial unit. They feel the same as imperial units.