Leaving phone plugged in bad for long term battery life?

[travbrad]

I've always heard that you get better long-term battery life when you only let your phone get down to around 40%, rather than say waiting till it's down to 10-20% or charging it when you are still at 80%. I've also heard the same about not always charging your phone to 100% This seems to be optimal in terms of degrading your battery more slowly over time, for complicated technical reasons of how the batteries work.

So all that being said, say I'm just at home browsing the web, watching some youtube, etc. Is it harder on the battery to just keep it plugged in while I use it? IE, would it be better to just run off battery and try to remember to charge it around 40%?

 

[Deleted member 245375]

Theory goes that charge cycles to 80% of charge capacity will prolong the overall lifespan (meaning the time measured in years, not per charge or hours) of a Li-Ion or Li-Poly battery according to most of the available research so there's probably something to that to various degrees. There are apps out nowadays that alert the user to a charge level set by the user and they typically default to 80% so as to notify you "OK, you hit 80%, unplug now..." I've used those types of apps myself on various devices and never really noticed it did anything more than prevent me from getting more lifespan as measured in hours of use, really.

The traditional thinking is charge a device to 100% and unplug it, using it on battery power till it tells you - typically at about the 15% level - that it's time to charge the battery and I've personally never had a single issue using devices in that manner. My own personal adjustment to that is once or twice a month I will use a device down to that level and then do a full charge on it but typically I don't worry about it all that much and leave the phone charging to 100% and then let it stay plugged in till I need to go mobile with it or have it someplace else. That's just me, as stated, my own way of doing it so don't take it as the gospel of battery charging or anything, but I've never had issues with it myself.

I don't go for devices without removable batteries, as a matter of preference, and I usually do have at least one extra battery for a given device. My current smartphone is an LG Stylo 2 Plus and I do have a second battery for it and I swap the cells maybe twice a month (not directly at the same time I do the usage to 15% and charge to full capacity however) so that I ensure I get a longer overall lifespan (again as measured in years) from both the batteries.

Modern devices have charging circuits that are somewhat "intelligent" and will stop the charging when the battery itself says "OK, I'm full..." and then the device will be running off the attached charger directly with a minor trickle to the battery based on usage. Some folks will play games or some other very intensive CPU/GPU activity and depending on the power output of their charger (as measured in mAh) might not be enough to provide the juice necessary so the battery gets called into play and you can see the battery charge actually drop over time during such activity. That's when you'll see a device getting even warmer than normal during heavy charge cycles because a) the battery is trying to power the device which is requesting so much power during a period of high CPU/GPU and even high brightness and b) it's also trying to charge itself which can pull more current than normal for a given level of charge.

My basic advice is this: charge the device to capacity and if you want to use it for basic purposes it's fine to leave the charger attached and the charging circuit will switch over as required. If, however, you want to play games or something else that requires high CPU/GPU and brightness meaning high power drain then disconnect the charger to keep it running somewhat cooler overall and use it as long as the battery's charge will last, then plug in and charge it back up but don't use the device for high CPU/GPU or brightness while charging. The reason I say this is because if the device gets hot during that activity that's one thing, but if the device gets hot AND the battery itself gets hot because it's trying to provide power and charge itself at the same time that makes the battery itself get warm and that's not good for Li-Ion or Li-Poly batteries: heat is what causes their overall lifespan (years) to suffer more than charging them frequently does.

Heat is the enemy so, whenever and wherever you can do anything to alleviate heat buildup in the battery (but also inside the phone itself) it's generally recommended. Gaming is pretty much the only activity on a smartphone that will increase the overall temp of the device because it uses a lot if not all the available CPU resources, it obviously hits the GPU hard to provide the graphics, and of course a lot of people will ratchet up the screen brightness (the biggest power draw of all on most devices) so that's 1-2-3 things all sucking down battery capacity at the same time. Trying to charge a battery with power input while it's trying to provide power output is just not a good thing.

Watching videos, long ago being a difficult CPU intensive thing, are now done almost exclusively with the GPU and hardware accelerated decoded done on the GPU alone and that requires very little CPU resource at all. In fact, once again, when most people watch videos they'll crank up the screen brightness and that alone is like 25x more battery usage than the actual video decoding is at any given time. I personally watch videos on my device at roughly 75% brightness, never been an issue for me but I know a lot of people that leave their screens at 100% 24/7 and it's a crazy silly waste of battery power.

 

[YeuEmMaiMai]

plug my phone in every night and never had issues with decreasing battery life. Nokia Lumia 810 still holds a decent charge Nokia 521s still hold a decent charge and Lumia 810 holds a decent charge and finally the 950XL are all still kicking strong on their original batteries.

letting the thing totally discharge before recharging will net you a shorter battery life vs more frequent charging were you are not keeping the battery heated up for a long charge cycle.

 

[Justintoxicated]

I charge to 80% during the work day (app notifies me), but always go to 100% overnight. Helps to minimize wear without being too annoying. I try to charge before 20% but I am not that great about that either. When you want to use your phone you want to use it.

If you think your battery life does not get reduced from charging cycles you are wrong. Lots of apps exist to monitor that. Currently I'm using Accubattery and I have 98% health still, but it started at 105% of expected capacity (3450 mah).

 

[yowen]

It's for this reason I like to buy phones with user-replaceable batteries. I can treat my battery however a darn-well please. I buy my phones used about every 18 months or so for 100 to 150 bucks. Currently using a Note 4.

I think this is a subject you can definitely overthink, as Justin mentioned above his battery that he charges fully every night is still fine. This is exactly what I do and I don't think it's particularly punishing to the battery, it may not be ideal. But I also don't lose sleep trying to optimize my charging behavior. I think it's (roughly) analogous to spending that next $5k to gain 1% in performance from your gaming PC, it's such a diminished return, it's not worth it.

 

[Justintoxicated]

It's for this reason I like to buy phones with user-replaceable batteries. I can treat my battery however a darn-well please. I buy my phones used about every 18 months or so for 100 to 150 bucks. Currently using a Note 4.

I think this is a subject you can definitely overthink, as Justin mentioned above his battery that he charges fully every night is still fine. This is exactly what I do and I don't think it's particularly punishing to the battery, it may not be ideal. But I also don't lose sleep trying to optimize my charging behavior. I think it's (roughly) analogous to spending that next $5k to gain 1% in performance from your gaming PC, it's such a diminished return, it's not worth it.

Yea, If I had a replaceable battery I would always just charge it to 100%, I always charge my 18650's laptops all the way, batteries are supposed to be consumables, but these days entire devices are made to be consumables by making the batteries very difficult to replace.

 

[yowen]

Yea, If I had a replaceable battery I would always just charge it to 100%, I always charge my 18650's laptops all the way, batteries are supposed to be consumables, but these days entire devices are made to be consumables by making the batteries very difficult to replace.

Which is insanity given the $1k+ price tag on flagship phones these days. And they sure are nice phones, but I can do almost all of the same stuff on my Note 4 for now. Which for me at the moment is mostly nav/browsing/texting/pictures/rollercoaster tycoon, lol.