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B How does charging and depleting a battery makes it last longer?

  1. Mar 5, 2017 #1
    Recently i bought a laptop with my friend. So, i went home charged it fully and begun to use it. However, my friend informed me that Acer recommends users to charge and deplete battery up to 3times.https://sg.answers.acer.com/app/answers/detail/a_id/27666 [Broken]

    I was confused over this. Shouldn't the threshold of the battery's lifespan be based on the voltage/potential difference that the battery can withstand along with the current output. Afterall, we are simply reversing the current flow when using the battery in respect to charging.

    Am i getting the purpose of the charging-depleting wrong or missing something out?

    P.S. How to insert a picture on this forum? Also, sorry if i posted this forum on the wrong sub-forum, am new to the forum.
    Last edited by a moderator: May 8, 2017
  2. jcsd
  3. Mar 5, 2017 #2


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    You are reasoning as though batteries are some kind of ideal device. Not true. Batteries contain chemicals. I'm sure the process has to do with that although I don't know details. I DO know that it is quite common to read battery warning about whether or not you should or should not let them get too close to fully depleted, at the risk of suffering degraded performance thereafter.
  4. Mar 5, 2017 #3
    I recently listened to a podcast related to that subject (not an English podcast, sorry).

    What it mostly comes down to is that every charge and discharge there is some type of chemical reaction associated with it. However, in addition to this intended reaction, there are "parasitic" reactions that also happen, and these slowly degrade the battery. Depending on the type of battery, these effects happen more in certain times, e.g. for some batteries the effects can be reversed when fully discharging and fully recharging. For other batteries they are voltage dependent, that's the reason why you often can charge a battery to 80% in a short time, but the remaining 20% takes the same time (what happens is that during the 80% it drives a high current through the battery, but because resistance is low, the voltage stays within safe parameters. But, when the battery approaches full level, the resistance goes up, and thus because of V=IR you have to lower the current in order to not exceed the voltage that would degrade the battery)
  5. Mar 5, 2017 #4
    Would like to know more about the degrading of batteries at the elctrodes in simple terms if possible. Tried googling it but the results were too advanced for my current knowledge...
  6. Mar 6, 2017 #5


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    Sometimes a few full cycles are used to calibrate the "fuel gauge".
  7. Mar 6, 2017 #6


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    If you have 73 minutes to spare, this video explains a lot about the Li-ion battery life cycle.

    It doesn't directly answer your question though, about why Acer might recommend charging and depleting the battery 3 times. My guess (somewhat based on something he said in the video) is that, during the first three cycles, the parasitic reactions are creating a solid barrier which slows down additional reactions. So the performance is stabilizing and the internal microchip is learning about the capacity of the battery.
  8. Mar 6, 2017 #7


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    We shouldn't be too surprised that no one wants the 'public' to know about such things. Battery technology is a very competitive business and designers / manufacturers do not want to share valuable information about the fine difference between their model and someone else's.
    You can get loads and loads of information about Lead Acid cells because 'everyone' knows about the technology.
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