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Hello fellow Android enthusasts,

I recently bought a Nexus7 that I want to use for development. The thing is, every time I connect it to my USB, in order to test some apps on it, it starts charging. Now, i know that this is absolutely normal for every device, but I am also concerned that the constant charge/discharge cycles can shorten the life of the battery. What do I do?

Do I need to get concerned at all? I mean, if it reduces battery life with something like 1% per year, I am totally fine with it. Yet, if it is a significant drain, how can I prevent it from charging unless I am charging from a charger?

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Charge/discharge cycles are mostly irrelevant for li-ion batteries. The main source of capacity loss is simply time. A li-ion battery sitting unused in storage will lose 15-20% of its capacity per year (see charts on page 4). Any minor losses from cycling is going to get drowned out by that.

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I haven't heard about number of charge cycles affecting battery life. However...

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

dwelling in a full state-of-charge for an extended time can be more stressful than cycling.

Most Li-ions are charged to 4.20V/cell and every reduction of 0.10V/cell is said to double cycle life.

Keeping Li-ion battery in high state of charge will reduce it's lifetime. Some laptops have Battery care function (software) to limit maximum charge to 80%. It's recommended by them if you routinely run on AC.

On android there is some kernel modifications allowing you to limit maximum charge in similar fashion. (it's from 2011) http://forum.xda-developers.com/nexus-s/development/mod-battery-life-extender-blx-t1257497

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    Most of my devices' manuals set this extended period of time in full-charge to between a week to a month. I am pretty sure you can left the device plugged at full charge for several hours with no problem (all of us probably do that every night already). – Mindwin Sep 23 '14 at 18:57
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Have you guys ever heard of Chargie? It's a USB stick+Android app combo that limits charging externally (no root needed). Just install the stick between the charger and phone and use the app to select the charge level. Simple as that. Look for "chargie stick" on Google.

Even if you want to charge to 100% - it will go there but disconnect power completely until charge goes down to 97% (a few hours). Then it will reapply charge, but that's way less stressful than normal trickle charging. However, given today's battery capacities, 90% is enough to get you out of most days.

Disclosure: I am the CEO of Lighty Electronics. We developed Chargie and would love people who have had this issue to enjoy our product as much as we do. No spam, just the solution to the problem.

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