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Does slowly charging (like usb: 500mA) a battery of a cellphone/ tablet/ notebook increase the overall lifetime of the battery itself?

If yes: why is it ? Why do LiIon batteries lose capacity over time (no matter how and when charged)?

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  • \$\begingroup\$ Sort of, to my understanding it is only going to reduce the lifetime if you charge it too fast. In actuality, giving it a certain amount of current allows it to heat up which helps with charging. \$\endgroup\$ – Jarrod Christman May 12 '15 at 13:11
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Short answer: Yes.

Before giving the long answer, think about how fast-charging a lead-acid battery works. Applying a lot of current raises its voltage; however, the negative plates are not able to react with the sulfuric acid quickly enough, and so the excess voltage is not helping it charge faster. On the other hand, the high voltage does damage the inside of the battery, thus reducing its life.

Long answer: when lithium ion batteries are given the high amperage, they are unable to "refuse" fast-charging, like lead-acid batteries do. As a result, the chemical reactions are forced to happen at a quick rate. Some chunks react quicker than others. The end result is, uneven charging of the battery. This unevenness adds up with time, and its capacity decreases.

Now the point is, any speed of charging for a lithium ion battery causes unevenness. A faster rate causes more unevenness; a lower rate causes less unevenness. If a battery heats up while getting charged, it is more malleable, and accordingly more susceptible to damage. Therefore, no matter how slowly you charge a lithium ion battery, over time its internal organization decreases, and it loses capacity.

Note: I am sweeping a lot under the rug to give a simple answer. The underlying reactions that I am calling unevenness have to do with how well the lithium ions can travel between the positive and the negative electrodes, and also whether they get converted to a different form due to local overcharging/overdischarging. I can give more detail if you're interested. The exact chemicals depend on the type of lithium battery.

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  • \$\begingroup\$ Thank you very much for the already good answer. Since it is a few weeks now since I asked the question, I was not expecting any answers. I'm very interested in the chemicals, because I had it at high school. I would appreciate any further informations, and sources for further information-gathering. \$\endgroup\$ – Joel Jun 22 '15 at 2:22
  • \$\begingroup\$ So which chemistry type would you like to know more about chemicals? (e.g. LiIon, LiPo, LiFePO4, etc.) \$\endgroup\$ – Alex Jun 22 '15 at 2:33
  • \$\begingroup\$ I think the most popular are LiIon and LiPo aren't they? In most smartphones are built in LiIon aren't there? So I think if you could explain those it would be great. \$\endgroup\$ – Joel Jun 22 '15 at 2:49
  • \$\begingroup\$ How much difference is there typically between the state of the "worst" parts of a battery and the best parts? If one had a product whose batteries could, in total, supply twice as much power as the device needed (but the device had that many batteries to increase running time), I wonder how much such a device could improve longevity by minimizing use of degraded cells? \$\endgroup\$ – supercat May 26 '17 at 17:51
  • \$\begingroup\$ @supercat This really depends on how much you "fast-charge"-- and also, "fast-discharge" your cell. In parallel designs, the cells on the ends tend to be more damaged. After optimizing my charging and discharging algorithms, I have yet to see a battery fail due to repeated charge cycles-- though a few failed either because I leave them in the sun in my car, or because I try to use them while they are frozen, or because I reverse polarity and discharge them below 0V. So unfortunately, I cannot give an exact number. @ Joel unfortunately I missed your notification. If you need something, ask \$\endgroup\$ – Alex May 30 '17 at 21:52
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If you look on "Battery University" you will find that all batteries deteriorate with time as the materials in the battery slowly decompose.

To get the most energy out of a battery over its full lifetime you should only charge it up (not too fast) to 90% and only discharge it to 50% (no more that C/5). The downside is that you only use 40% of the batteries capacity.

Suggested charge/discharge rates quoted by manufacturers are to achieve the best capacity (mAh) of the battery with a reasonable lifespan. It's all a trade off.

Hope this helps

Dingus

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