3 commenti su “(English) Why Android sucks at managing battery drain and discharge”

  1. I stumbled across this while searching for the answer to your question. Why did they do it this way?

    I’ve done a LOT of work with lithium ion batteries. Both professionally, and as a hobby. Everything I’ve read here is pretty much accurate, except for one statement:

    “…I know the battery state of charge cannot be determined by voltage alone…”

    Now I must clarify. This is actually a true statement in many cases. And you are indeed correct that temperature and useage come into play. But our phones discharge so very slowly that you actually CAN use the voltage to determine battery state. It isn’t linear, but the discharge curves of these batteries are so well documented that it takes a very simple lookup table to pull the values from. Will they be exact? No. But will you, the user, notice even 5% error in the value? Not likely.

    The reason this can be done, as I said, is because of how slowly we discharge the batteries. In the industry, we measure discharge in C, C being the capacity of the battery, but remove the “hours” portion of the milliamp-hours. So a 1500mAh battery could be said to discharge at 1C if you put a 1.5 amp load on it. In that case it would take one hour to discharge. At 2C, or 3 amps, it would take 1/2 hour, or one over C. I discharge my high performance batteries at 20 and 30 C. That’s fast. We discharge our cellphones at 0.1C or less. That’s slow.

    Not all batteries are created equal, and many cannot handle the high discharge rates that I put them through. However I’ve yet to see a battery that couldn’t handle a meager 1C. 1C would mean our phones would die in an hour. The fact that we typically get at least 10 hours of life means we are in the .1C range. Really, anything below half of a battery’s nominal output is low enough that the discharge curves tend to lie mostly on top of one another. Sure, there are differences, but they are within 5%, or something the user would never notice anyhow. Proof? I worked on an electric UAV (drone) for a company here in town. Based on voltage alone during a couple of test flights, along with lithium battery discharge curves, I estimated a 3 hour total endurance limit. On test day, we got the low-voltage cutoff at 2:59. Good enough for military work, and more than adequate for cellphone use. By the way, that is a 0.33C discharge, and we weren’t even using high performance batteries.

    This is the reason that WinMo phones, and the old Nokia that you mentioned have such accurate battery readouts. Well, accurate enough. And as you seem to have noticed, swapping batteries really tends to confuse Android OS, and it starts to read all kinds of crazy numbers. I’ve had mine shut down at over 3.8 volts before. That to me, is insanity.

    Honestly, I don’t mind them collecting data. I’d like to see what features, functions, and apps drain the battery the hardest. But base my phone’s display and cutoff on the voltage, PLEASE. Cut it off at 3.2V for all I care, there’s not much left under the curve at that point anyhow, but not becuase the corrupt data shows that my battery MIGHT be dead.

    I really don’t know how non-rooted users survive, as I have to recalibrate every month or so…

    1. One thing I can say is: THANK YOU 😀
      Your comment is quite enlightening, and that “state of charge cannot be determined by voltage alone” was written more to appease those readers that I expected would bash me for a possible “scientifically untrue” statement. But otherwise, I’m sure my battery cannot be dead just because a “history lookup table” says so, even if the battery driver reports just barely below the 3600mV mark (!!!) And that’s when I deleted the battery stats, because otherwise I would get there sooner.
      I mean, c’mon.

  2. u ur phone is rooted then use a xposed module called disablecriticalbattery .. it can shift or disable automatic shutdown occuring because of low battery

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