Li-Po batteries degrade far faster when their charge level is at the levels the manufacturers call 0-15% or 85-100%; the exact minimum and maximum charge levels are a manufacturer decision that trades off total battery capacity when new against battery life. Manufacturers make the decision by thinking about what is most profitable for them, which is the biggest possible advertised (brand new) battery capacity, while dying quite fast (within a couple of years) to sell more, but not so fast consumers can claim it is faulty.
So they will happily make the battery last 1/5th of the life it otherwise would, for +30% brand new battery capacity, even if that 30% will be gone in a year of typical use.
Those decisions are aligned to the manufacturer’s interests, but they are seldom aligned to a consumer’s interest. Most consumers would be better off with 30% less battery capacity, but a phone battery that lasts 5x as long - many people for example charge every day, and only get down to 80% or something anyway.
The way to re-align to your interests are to: stop charging above 85%, and shut down at 15% instead of going down to 0%. You can do this manually, but it is a real pain; you can’t just plug it in, and leave it until it is charged, you’d need to micromanage charging. Some more responsible manufacturers (e.g. some Samsung devices) have features that will do this for you if you set preserve battery mode. Others, including Google, however, really don’t want you to do this, because it hurts their sales. They don’t provide standard APIs available to unrooted devices that would allow apps that do this.
If you are willing to root your device (and ideally install a third party Android distro like LineageOS), you can install ACCA (https://f-droid.org/packages/mattecarra.accapp/) on a rooted device, and set it to stop charging at 85%, and shut down at 15%. This will increase your battery life very significantly, and drastically slow the decline in capacity you’d otherwise see. Unfortunately, many manufacturers hate people taking control of their own devices this way; Google has unfortunately convinced major banks etc… to use their so called “Play Integrity API” to check that your device is “secure” (where secure is defined by Google as including a phone no longer receiving security patches, with known vulnerabilities that let someone trivially install a keylogger over the wifi, but excluding the same phone rooted by the owner, with a highly secure up-to-date LineageOS install, with extra security software like firewalls that stock Android wouldn’t allow, and with ACCA installed; it’s almost like “secure” means toeing the Google line, and the banks have been conned). There are sometimes ways to pass the Play Integrity API checks even when rooted, but Google is constantly battling users to try to break them. But it might be worth it for better security and battery life.
Tip for increasing the life of your next battery:
Li-Po batteries degrade far faster when their charge level is at the levels the manufacturers call 0-15% or 85-100%; the exact minimum and maximum charge levels are a manufacturer decision that trades off total battery capacity when new against battery life. Manufacturers make the decision by thinking about what is most profitable for them, which is the biggest possible advertised (brand new) battery capacity, while dying quite fast (within a couple of years) to sell more, but not so fast consumers can claim it is faulty.
So they will happily make the battery last 1/5th of the life it otherwise would, for +30% brand new battery capacity, even if that 30% will be gone in a year of typical use.
Those decisions are aligned to the manufacturer’s interests, but they are seldom aligned to a consumer’s interest. Most consumers would be better off with 30% less battery capacity, but a phone battery that lasts 5x as long - many people for example charge every day, and only get down to 80% or something anyway.
The way to re-align to your interests are to: stop charging above 85%, and shut down at 15% instead of going down to 0%. You can do this manually, but it is a real pain; you can’t just plug it in, and leave it until it is charged, you’d need to micromanage charging. Some more responsible manufacturers (e.g. some Samsung devices) have features that will do this for you if you set preserve battery mode. Others, including Google, however, really don’t want you to do this, because it hurts their sales. They don’t provide standard APIs available to unrooted devices that would allow apps that do this.
If you are willing to root your device (and ideally install a third party Android distro like LineageOS), you can install ACCA (https://f-droid.org/packages/mattecarra.accapp/) on a rooted device, and set it to stop charging at 85%, and shut down at 15%. This will increase your battery life very significantly, and drastically slow the decline in capacity you’d otherwise see. Unfortunately, many manufacturers hate people taking control of their own devices this way; Google has unfortunately convinced major banks etc… to use their so called “Play Integrity API” to check that your device is “secure” (where secure is defined by Google as including a phone no longer receiving security patches, with known vulnerabilities that let someone trivially install a keylogger over the wifi, but excluding the same phone rooted by the owner, with a highly secure up-to-date LineageOS install, with extra security software like firewalls that stock Android wouldn’t allow, and with ACCA installed; it’s almost like “secure” means toeing the Google line, and the banks have been conned). There are sometimes ways to pass the Play Integrity API checks even when rooted, but Google is constantly battling users to try to break them. But it might be worth it for better security and battery life.