Does leaving plugged in harm battery?

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I turn my phone on Airplane mode and unplug at night while I'm sleeping.

BUT! When at work and at home at other times, is it bad to leave it plugged in 100% of the time? (I.E. does it decrease total battery life over a few years to be constantly charging.)

Or is it better to unplug ASAP when it hits 100% and let it drop to 20-30% and recharge-unplug-recharge-unplug etc? (If so, how much of a difference would this make?)

And does it matter USB vs AC source? I know USB is half the amps, so this could have an effect too?

Honestly, the battery is going to deteriorate a bit either way over a year time span. It is probably best if you just replace the battery every year.

Originally Posted by Paul22000

I turn my phone on Airplane mode and unplug at night while I'm sleeping.

BUT! When at work and at home at other times, is it bad to leave it plugged in 100% of the time? (I.E. does it decrease total battery life over a few years to be constantly charging.)

Or is it better to unplug ASAP when it hits 100% and let it drop to 20-30% and recharge-unplug-recharge-unplug etc? (If so, how much of a difference would this make?)

And does it matter USB vs AC source? I know USB is half the amps, so this could have an effect too?

Doesn't matter. All you need to really be worried about is that you leave it on the charger long enough to get a true 100% charge, and you don't always put it on when at 80%, try and run it down from time to time to 10% type thing.

If you leave it on the charger 24/7 for a year, it will have no real effect on the battery that a year of use wouldn't do, and you might actually come out ahead since battery life times are based on charge cycles... when on charger, as you are asking about, there would be virtually no charge cycles.

Originally Posted by pjcforpres

If you leave it on the charger 24/7 for a year, it will have no real effect on the battery that a year of use wouldn't do, and you might actually come out ahead since battery life times are based on charge cycles... when on charger, as you are asking about, there would be virtually no charge cycles.

Ooooh, interesting... Did not know that. I thought that leaving it charging was the worst case possible.

But let's be honest.

How long do you think you'll keep the phone?

I've never had one more than a year...

Originally Posted by Amdathlonuk

But let's be honest.

How long do you think you'll keep the phone?

I've never had one more than a year...

Til the Nexus Two comes out bro

[Edit]: Well, my thinking is how BAD could this affect it. Like leaving it plugged in all the time = 50% battery capacity in 4 months type of thing. I guess that is not the case though eh?

Originally Posted by Paul22000

I turn my phone on Airplane mode and unplug at night while I'm sleeping.

BUT! When at work and at home at other times, is it bad to leave it plugged in 100% of the time? (I.E. does it decrease total battery life over a few years to be constantly charging.)

Or is it better to unplug ASAP when it hits 100% and let it drop to 20-30% and recharge-unplug-recharge-unplug etc? (If so, how much of a difference would this make?)

And does it matter USB vs AC source? I know USB is half the amps, so this could have an effect too?

To add to what pjcforpres said, I would suggest topping off the battery a couple times a day rather than always letting it run down to 20-30% (deep cycling) the battery. Deep cycling is worse for Li-ion batteries. It causes more heat for longer periods of time when you do charge. I would only discharge completely once every few months to keep the battery calibrated.

My personal habit is to top off frequently. If I'm at home, I'll let it charge to a true 100%, like pjc said, then take it off the charger and leave it off till it hits 75-80% and top it off again.

i can add to this discussion what i've learned about lithium-ion batterys


having it plugged in, while it is being taxed heavily (playing games) and already at 100% is a bad idea, then i discharges and recharges all over the time.
When it isn't full and you plug it in to top it off it shouldn't really do any harm, as long as you disconnect it when it's at 100%.


Emptying it completely also lowers overall capacity, 10% is a good threshold when to charge it.


When leaving it off to store it for a while, store it with around 70-75% in the battery. Storing it fully charged also lets capacity down.

Originally Posted by creepinshadow

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Emptying it completely also lowers overall capacity, 10% is a good threshold when to charge it.

I thought you WANTED to do this? I've heard calibrating it is running it until it turns OFF?

Originally Posted by Paul22000

I thought you WANTED to do this? I've heard calibrating it is running it until it turns OFF?

I respectfully disagree with creepinshadow's suggestions. I've read up on lithium ion batteries considerably in the last few years. 10% is not a good threshold to always charge your battery from... that's deep cycling and was great for nickel metal hydride, but isn't good for lithium ion. That said, there's no way for it not to get that low from time to time if you're away from your charger for extended periods and I'm sure it's not going to destroy your battery as fast as one might think.

As for storage, the I charge (or discharge) mine to 40-45% then pop it into the fridge for storage. Read that in a long article explaining how to treat li-ion batteries.

Like you said though, a full discharge for calibration is running it till it turns off then plugging it in while keeping it off until an hour or so after the light turns green.