The following are specific measures on how to maintain the Iphone battery
Apple designs all the parts in the iPhone so that they all work in harmony with each other. Everything includes the shell. Ideally, you don't need a third-party case to cover your iPhone. The stock case alone is enough to protect the internal components and allow the device to charge the battery without overheating it. Adding an extra case could cause the battery to heat up faster than engineers designed it to.
If you find your phone uncomfortably hot while charging and can't resist using a third-party case, we recommend removing it before charging your device. Not all third-party phone cases generate too much heat during charging, so if the phone seems to be running fine and isn't generating extra heat, you can leave it as is.
Keep Iphone battery at room temperature
Lithium batteries can work well under pressure and in a wide temperature range. Ideally, you should only use the phone (or discharge the battery) between 62° to 72° F (16° to 22° C). Using your device at temperatures below freezing or above 95° F (35° C) may cause permanent damage or accelerated capacity loss. The moment the battery (not the phone) leaves the factory, it has already started to lose capacity at a slow rate. Once it is installed in the phone and starts to use normally, the degradation will be a bit faster. The more you use it and the more charge cycles you have, your battery will start to lose capacity permanently. That's why iPhone batteries finally start to degrade significantly after two years of unboxing. The constant discharge and charge cycles, day in and day out, constitute wear and tear on the battery until it eventually drains.
Battery decay can happen faster if you don't protect your device by discharging or charging it in extreme ambient temperatures. Your iPhone software is designed to intervene when it detects that the charging temperature threshold has been exceeded, limiting battery charging to 80%, but this may not always work. Charging or using the phone in ambient temperatures above 95°F can also cause serious battery problems. The same is true when the battery is exposed to extreme cold.
As a general rule, treat your iPhone like you would yourself. You work best when you're at room temperature, so do the same for your phone. Leaving it in a hot car on a sunny day is a surefire way to shorten battery life.
2. Low Power Modes and Performance Management
Low power modes are a quick way to extend battery life when you need it. The feature pauses mail fetching, background app refreshes, automatic downloads, and more with a single button. It's not an everyday type of feature (hopefully), but it's still handy.Check out this article How to Add Low Power Mode on iPhone
You can turn on Low Power Mode under Settings > Battery. However, it's useful to have quick access to Low Power Mode in Control Center. Navigate to Settings > Control Center > Customize Controls and tap the + icon next to Low Power Mode (if it's not there). Another feature similar to automatic low power mode is iOS performance management. Essentially, if your iPhone's battery has degraded, performance will automatically decrease to save battery and prevent it from turning off unexpectedly.
3. Auto lock and screen brightness
If you notice that your battery usage is higher than you expected on Home and Lock Screens, it's a good idea to check these settings.
A 30-second auto-lock will help you maintain maximum battery life. Especially since most of Apple's iPhones support raise to wake, 30 seconds is worth it.
Lowering the screen brightness can also help improve battery life, but this may come down to personal preference. You can do this in Control Center (swipe down from the top right) or Settings > Display & Brightness
4. Hot and cold temperature
Apple says the ideal ambient temperature for iPhone and other Apple devices is 62° to 72° F (16° to 22° C). Temperatures above 95° F (35° C) may "permanently damage battery capacity."
In addition to doing your best to keep your iPhone away from heat, it's a good idea to remove your iPhone case if you find it gets hot while charging.
Also, temperatures below 32° F (0° C) can temporarily shorten battery life. If you live in a cold climate, placing your iPhone in an inner pocket closer to your body can help extend battery life by keeping it warm.