I usually disconnect my cellphone from the charger some time after it's fully charged because I'm afraid the battery could lose capacity over time if I don't. However, I believe modern electronics should be able to handle this kind of scenario and automatically stop charging the battery once it's full. Does this apply to modern Android phones? Or do I need to continue disconnecting it all the time?

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    If you leave a cellphone constantly connected to its charger, 24 hours per day, 365 days per year, it will put extra wear and tear on the battery. Instead of wearing out after the usual three years, the battery might wear out after just two years. Once the battery is worn out, it won't hold as much energy anymore. You'll probably want to replace it. – unforgettableidSupportsMonica Jul 14 '16 at 9:00
  • (When you do replace the battery after a few years, avoid the unsafe counterfeit batteries sold by small online vendors. Many counterfeit batteries are indistinguishable from real batteries. Instead, spend US$25-$50. Choose a good-quality battery made by your phone's manufacturer or by a reputable aftermarket-battery maker such as Lenmar. Purchase the battery from a reliable vendor. In America, Best Buy is one reliable vendor.) – unforgettableidSupportsMonica Jul 14 '16 at 9:04

As njd pointed out, most cell phone batteries are Lithium Ion now.

Although constant charging cannot hurt, it looks like you may want to periodically run the battery all the way down so the digital circuits can correctly calibrate:

Although lithium-ion is memory-free in terms of performance deterioration, batteries with fuel gauges exhibit what engineers refer to as "digital memory". Short discharges with subsequent recharges do not provide the periodic calibration needed to synchronize the fuel gauge with the battery's state-of-charge. A deliberate full discharge and recharge every 30 charges corrects this problem. Letting the battery run down to the cut-off point in the equipment will do this. If ignored, the fuel gauge will become increasingly less accurate.


Great set of Lithium Ion battery use tips here: http://www.batteryuniversity.com/parttwo-34.htm







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    @jeff, I have never seen an answer from you off of meta, but I must add a comment, "Although constant charging cannot hurt, it looks like you may want to periodically run the battery all the way down so the digital circuits can correctly calibrate:" is not good advice. This strains the battery, if your charging circuit has a light error on showing how much charge you have left is a minor detail, but stressing your battery can cause problems. – Kortuk Jan 23 '11 at 17:04
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    @kortuk that's fine, do you have a citation for that? – Jeff Atwood Jan 23 '11 at 21:12
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    @JeffAtwood, yes I do, my answer about charging cellphones elsewhere on this site discusses it. Also, to link directly to a source, scroll down to the bottom and read the "Simple Guidlines". I have also worked with lithium batteries a lot in a professional capacity at the last start-up I worked at, and these sources are backing for me, not the source of my knowledge. – Kortuk Jan 23 '11 at 22:15
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    @JeffAtwood, I have seen battery monitors that need this to stay 100% accurate, but it is a trade-off between battery life and knowing exactly charge left. Most people will chose to know their charge left, I just suggest that you note to people that this does age the battery significantly. You are not wrong, I just think it needs a disclaimer. – Kortuk Jan 23 '11 at 22:16
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    Never intentionally discharge a lithium ion battery to 0%. It will shorten the lifespan, and in rare cases it will cause the battery to no longer function. – Sepero Nov 16 '12 at 12:12

Modern cell-phones all use lithium-ion batteries, which work best with frequent top-up charges.

They have circuitry to monitor the input voltage and prevent over-charging.

Some chargers get quite warm while connected to the mains supply, and that's just wasted energy; so you might want to disconnect the charger from the mains once your cellphone is fully charged, but there will be no damage to the battery if you leave it charging a few hours longer.


All devices should stop charging once they're full. However, they might start recharging when the charge drops down to 80-90% depending on the manufacturer.

If I'm rights most batteries should be rated for about 1000 charge cycles before serious degradation occurs. If you charge the phone at night, in the car and at work that would be about one year. After that you might as well buy another battery since they are getting really cheap. Just dispose of the battery environment friendly.

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    Can you provide a source? "If I'm rights" is not encouraging. – reducing activity Jan 30 '17 at 6:57

The phone I have (OpenMoko FreeRunner) specifically states in the documentation that it will live happily on the charger; it was made in 2006 or so.

If your phone's charging circuits are sophisticated enough it should be able to trickle charge and not overcharge or poorly condition the battery.

  • Is that a GTA02v5 or v6? – ott-- Feb 17 '15 at 19:31

Here are the real expert answers from Electrical Engineering, our sister site:

Effects of smartphones always connected to AC power?

Not directly related, but also a nice read:
Tricking the charging circuit considered harmful

TL;DR: The charging circuit is safely engineered to be connected to the charging circuit 24/7.


Modern electronics will not overcharge battery, and phone should be able to handle being constantly plugged in. However keeping battery constantly in high state of charge and charge cycling in high voltage will increase battery degradation. It's best for battery when phone is minimal time in full charge.

My personal experience is that my android phone SGS1 handled overnight charging all well so it's not wise to get too worried about this, but if your battery newer last long keep eye on that.


Some portable devices sit in a charge cradle in the on position. The current drawn through the device is called the parasitic load and can distort the charge cycle. Battery manufacturers advise against parasitic load while charging because it induces mini-cycles, but this cannot always be avoided; a laptop connected to the AC main is such a case. The battery is being charged to 4.20V/cell and then discharged by the device. The stress level on the battery is high because the cycles occur at the 4.20V/cell threshold.




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