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You can get a voltage sensor that is accurate to three decimal points for literal cents, so yes, your phone does know how much energy is left in the battery. It also has current sensors, so knows how much energy is being used.
It does not know the capacity loss of the cell over time. That is why you should let the battery go completely dead and then charge it to max capacity as this will recalibrate the coulomb meter on the battery manager - batman
My understanding is that happens constantly as the battery is charged and discharged.
It tries but the value is floating until it actually has a full charge cycle. There is no way to know what the entire voltage range is. You're getting into how efficient the chemistry is over time and that is impossible to measure. It can be estimated, but that is all theoretical and not real. When the battery is fully discharged, the time, temperature, and current can be used to determine Coulombs and that is the actual energy capacity.
I'm not an expert, but I have built many circuits. My main experience here is in reverse engineering some gaming hardware that had an advanced battery management chip from Diode Semiconductors. That had such a Coulomb battery meter. The board was a 3 layer PCB and I took that as a challenge. The batman chip was also a small ball grid array (pins are inaccessible on the back side. I didn't have xrays when I did the first trace of all pins, so I had to fully understand the chip to trace all connections only using the vias. I think I have a chip or two in parts drawers that do the same thing, but I never built anything with them, or at least haven't yet.
Preach sibling
Idk how multiple super assertive people all got the idea that “voltage = battery percent” and all wanted to yell it at me the same time lol
I don’t think I am going to take confident proclamations about how it works from someone who thinks “voltage” translates to “how much energy is left in the battery”.
https://batteryuniversity.com/article/bu-903-how-to-measure-state-of-charge
I don’t really know how this stuff works, that’s why it is my conspiracy theory instead of me just giving fun facts. But, I don’t think you know how this stuff works either.
It sounds like coulomb counting (current sensors, as you said) is often the method. Personally, I suspect there’s a decent amount of bullshit inserted into that to make it look “normal” when people are looking at how the number behaves, at the expense of accuracy. You might move your phone from cold to warm for example, and the usable energy in the battery might increase when that happens (or something) but it’s definitely not going to show your battery percent going up, even if it could detect it properly which I don’t think it can. Whether to say that means it’s “bullshit” is I guess a matter of opinion.
Phones don't use lead acid batteries, genius. I don't know why you think that study is relevant.
Also, your phone knows what the temperature of the battery is, and almost certainly takes that into account, although this affects the output voltage but not the amount of energy stored.
Li-ion is worse. I looked up a few different articles, I just kind of picked that one at random because I didn’t want to spend more time on it. This one is pretty succinct about it:
https://www.pcbway.com/blog/PCB_Basic_Information/Important_Techniques_for_Determining_Battery_State_of_Charge_c46fe75a.html
“This method is not suitable for some other cell chemistries like lithium-ion, which has a negligible change in its voltage throughout most of its charge/discharge cycle.”
Which is why the phone also monitors charge and discharge, or current through the battery.
My new conspiracy theory is that a gang of people have teamed up to try to wind me up on this particular topic in what was supposed to be a lighthearted nonsense-question to which I gave an appropriate nonsense-answer.
You’re the only one who actually did arrive at something which is pretty much the actual answer (“coulomb counting”), although you keep mucking it up by saying things like you “can get a voltage sensor” to get the energy left in the battery, or “current through the battery” when the battery is the only part current does not flow through during discharge, or by making up wild random guesses that something is “almost certainly” taken into account. Just take all that extra stuff away and stick with “the phone monitors discharge” and you’ll be pretty much right.
Hopefully we can put this whole endeavor behind us now, and go back to talking about Chipotle and chemtrails.
It's very clear from this exchange that you don't know dick about electronics.
The evidence for my secondary conspiracy theory grows stronger