At LockerGnome.net, Robert writes:
I’ve had my Nexus 4 since late December; it’s a great phone! The thing is that, every night before I go to bed, I read social feeds to drain the battery and then I plug it in for a charge for the whole night. The question is: is it a problem if I leave my smartphone on a charge all night? Won’t the battery suffer from this?
This is a great question. Lithium Ion batteries are becoming far more common in smartphones than just about any other battery technology. This answer will focus on what effect this charging habit might have on these particular batteries.
To start: phones do have an automatic shutoff mechanism built in to prevent overcharging that might cause a potential fire hazard. If this is your concern, then rest at ease that the right charging hardware coupled with the right non-shady smartphone shouldn’t be a hazard to your person or property.
That aside, there are some compelling reasons to unplug your smartphone once it reaches 100% capacity. The reason for this is simple. As your phone runs throughout the night, it loses battery life. This causes the charging mechanism to kick in over and over again as measurable amounts of battery drain occurs during standby. Your phone checking email, receiving text messages, and various apps doing their updates can do a lot to your phone’s battery while you sleep.
Your battery may have a limited amount of charging cycles available to it throughout its life. Let’s say there are 1,000 cycles in your particular battery. If you charge 30+ microcharges (a fraction of a full charge) each night while you sleep, then you’re really eating away at your phone’s battery life. If, however, you only charge your phone when it needs it and make sure to unplug it after it hits 99-100%, then you’re only taking away one partial or full charge cycle each time you plug it in.
This doesn’t mean that your phone’s battery will degrade and die in one night, either. Like laptops, you can leave your phone plugged in almost all the time and it’s likely your battery will still last quite a while, but that doesn’t mean you aren’t at some level chipping away at its capacity or longevity by doing so. I leave my phones to charge overnight all the time, and it really doesn’t cause noticeable degradation to me. Does that mean it won’t over longer periods of time? Probably not for everyone.
Buying a cheap, knock-off charger can also have an adverse effect. Often, cheap chargers won’t respond so well to the shutoff mechanism in the phone. The energy may also come through in sporadic bursts, which isn’t good for your battery’s life, either.
You can see this effect when you plug your phone into your car charger and then into the auxiliary input in your car stereo. If the audio becomes fuzzy and distorted, then you have a pretty good indication that your phone’s battery might not be enjoying what it’s going through. Swap that power source out for one with proper insulation, and the audio might well be crystal clear.
Your phone’s battery is a fickle beast. It can die at any time and you rarely know when things are going bad until it’s too late. Calibrate your phone’s battery level indicator once per month by running the battery to zero, leaving it alone for five hours, and charging it to full. This will help you stay on top of exactly what your battery’s health is like.