Rukbat
Retired Moderator
Wrong. Once it reaches 100% it stops charging.IF you leave it at 100% on charge for a LONG time, it will wear the battery a bit over a long time.
Wrong. If you're going to store it for long period out of the phone, 40% is about the optimal charge, because the self-discharge rate will be lower. You're mixing two totally different things.IF you leave it closer to 50% it will last longer.
No, you're using it. A well-maintained lithium battery can last so long the phone it's in becomes unusable. (My V551 OEM batteries - over 10 years old - still give me about 95% capacity. They're about 20 years from being "worn out" and, at 72, I don't think I'll be alive by then - and GSM phones probably won't be used any more. [My StarTAC is still the best phone I ever had, probably the best one ever made, but you can't use one any more. No GPS.] Maybe in 20 years, phones will have to have something in them that we haven't even invented yet.)BUT, when using the battery, you are wearing it out.
That's not long life, that's long storage. You still have to check the SoC every 3 months or so to keep it at 40%. Leave it for 5 years and you have a piece of hazardous waste, not a battery. (Lithium is a hazardous material.)In other words, if it is unplugged and near 50% you are wearing it out. So the only way to get long battery life is to pull it from the phone at 50% and store it. Impractical.
Also not the longest life scenario. Charging the battery every time it drops to 90% will give you less total power over the life of the battery than charging it at 40%. (Carrying a spare battery - with a phone with a replaceable battery - is the easiest way to get the most out of your batteries. 40%? No charging capability? Swap batteries.)I have always plugged mine in if I am near a charger
See the second figure (the chart) at Battery University - How to Prolong Lithium-based Batteries. Cadex has probably analyzed more batteries in 2014 than all of us combined on this forum have owned over our entire lives. What they don't know about batteries isn't known, it's still being researched (like how to prevent dendrites in lithium batteries - no one knows how to do that yet). If you want the expert word, take it from the experts.
Tabish, my only argument with your original post is that modern batteries (manganese cobalt oxide positive poles and graphite negative poles) have a nominal voltage of 3.7 Volts, but they have a potential of 4.2 Volts while being charged, not "when fully charged". (As soon as you disconnect the charger, the terminal under load voltage drops to 3.7 Volts.) A lot of manufacturers currently charge their batteries to 3.85 Volts terminal voltage by holding them at 4.35 Volts during charging, but that shortens the life of the battery (while giving a slightly longer time between charges). Marketing has a lot of knowledgeless input to engineering these days. When the marketing VP says "this will sell more phones" and the engineering VP says "this will destroy more batteries", marketing wins out. Batteries that die after 6 months don't impact on the company's bottom line, selling more phones does.
No one has invented a new sub-atomic physics yet - manganese cobalt oxide as a positive pole and graphite as a negative pole still gives the same voltage it would have given 10,000 years ago. What we need isn't futzing with existing technology, what we need is a light, power-dense battery that can take constant full discharges, and fast charges. A car battery is still FAR better than ANY lithium chemistry - except for weight. Lithium is the lightest metal, lead isn't. But they're working on it. There's an industry that's bigger than the cellphone industry that's screaming for power-dense, deep-discharge light batteries - the automotive industry. And they'r driving most of the research. A dendrite in the battery of a hybrid or electric car costs the company US$2,000. Put that huge, heavy battery into a box the size of shoe box and we'll see phones with 2 month standby/2 day talk battery times.