Batteries Doomed To Fail?

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I've noticed that mine (and others report) their SGS3's run particularly hot. This is most likely due to the dual core processor, the processor seems to be located at the bottom right of the phone (by the back softkey) as this is where the phone is the hottest. Im in Arizona and during the summer temps outside are excessive constantly over 100F. Even when in my home all day I can rarely get my battery temp down to 85F. Li-Ion batteries have a much shorter lifespan when exposed to temps above 85 and when exposed to excessive temps are also prone to "thermal runaway" in which the cells become so hot that the battery continues to self heat until catastrophic failure in which there is so much pressure built up inside the battery that when the casing fails it essentially becomes a flamethrower. The dell laptop battery recalls were caused by this, a flame thrower in my lap doesnt sound fun but neither does one in my hand (unless im using a real one). The polymer plastic casing is a terrible heat sync (especially with a rubber case). It seems these batteries are going to need to be replaced once a year.
Looking at about a 35% loss in capacity within one year. I also experience terrible battery life, moderate use i get about 6 hours, screen eating up most of my battery and when in doors i keep the screen brightness all the way down.
Data found from multiple websites but do not have enough posts to site source

Wait.. You're complaining about your phone being 85f? Try over 100f lol mine gets to 42c.....very annoying

Sent from my SGH-T999 using xda premium

Sent from my SGH-T999 using xda premium

I got my phone there first day it came out and its rooted and overclocked and it stays around 28 C but goes up to ~40C at heavy use

Sent from my SGH-T999 using xda app-developers app

Yes, these batteries are doomed.

I have been looking into the charging PMIC and if you can tell it to stop charging at 80%, but it appears to be hard set at 4360mV where it goes into a trickle charge mode and runs the phone of the USB power.

The problem is two fold. For one thing we have a 2100mA battery, and the charger is 900mA, so a 0.5C charging is good for long term battery life, even better if you charge over USB at 500mA. But the discharge rate can be as high at 1000mA if you have all the bells and whistles on and things are hot to begin with. The typical usage with screen on is 200mA, maybe 400mA with WiFi, more with BT. But current increases greatly when both cores are over 1.5GHz.

So the problem mostly seems to be the charging is reducing capacity by people going below 10% charge (if you graph the voltage you can see the tail off below about 15%) and charging above 80%. LiIon capacity is reduced by keep over 95F and also permanently reduced by draining to low voltage levels and also charging much above 4.2V and then holding the voltage there. I noticed the capacity after two weeks was reduced by 20% already.

And no, the thermal runaway is no longer a problem and I wouldn't mention it anymore. The battery self-protects, as well as the system is being very careful monitoring the thermals. Also, the CPU is throttled above 56C ( I believe)

But, I know in the PMIC controls you can disconnect the battery and run only on AC when plugged in. This would be ideal to leave charge the battery to 80% then stop charging it, and you could leave it plugged in at work or overnight without worrying about the battery capacity.

You lost 20% capacity in 2 weeks??? Wow!
I've had mine for going on 2 months and my battery seems as strong as ever! Still able to easily get over 24 hours off a full charge and still be above 10%.

I am not trying to be argumentative here but isnt the idea that going below 15% and charging above 80% purely myth? I've seen quite a number of people posting the same info in the past but when asked for a reliable source for their information they are never able to produce one. Im pretty sure I've read articles/studies that debunked it as well. (Ill try to find them but honestly may be thinking of something else I read. Ill let you know either way if I find it)

I do know its a good idea to have the built-in function that stops it charging around 95-97%, but isn't that just to prevent overcharging?
Also I should point out that my phone does often get quite warm, even hot sometimes, but it hasn't affected my battery life in any noticeable way.

As for your 20% drop in capacity, have you flashed any roms? The latest jb leaks have big battery drain issues. Also when you flash any rom it can take a few full cycles for the system to relearn how to accurately report battery use and can often trick people into thinking the battery capacity has gone down.
Like I said, not trying to argue with you. It seems you tend do do your research on this type of stuff so im hoping you can point me to where people are getting their information.

Sent from my SGH-T999 using xda app-developers app