Managing Your Digital Stuff - Battery Health

All rechargeable batteries are consumable components that
become less effective as they get older-and their age isn't
determined only by time. A battery's lifespan depends on its
chemical age, which is affected by factors such as its
temperature history and charging pattern. As your device's
battery ages chemically, its charging capacity gets smaller.

Sage advice: Don't get caught with your battery down. Don't 
be out of juice when you need it most. 

Maximizing Battery Life and Lifespan Update to the latest software. Apple software updates often include advanced energy-saving technologies, so always make sure your device is using the latest version of iOS, macOS, or watchOS. Avoid extreme ambient temperatures. Your device is designed to perform well in a wide range of ambient temperatures, with 62°F to 72°F (16° to 22°C) as the ideal comfort zone. It's especially important to avoid exposing your device to ambient temperatures higher than 95°F (35°C), which can permanently damage battery capacity. That is, your battery won't power your device as long on a given charge. Charging the device in high ambient temperatures can damage it further. Software may limit charging above 80% when the recommended battery temperatures are exceeded. Even storing a battery in a hot environment can damage it irreversibly. When using your device in a very cold environment, you may notice a decrease in battery life, but this condition is temporary. Once the battery's temperature returns to its normal operating range, its performance will return to normal as well. Caring for your Surface battery Microsoft: Battery Status About battery health management in Mac notebooks System Preferences > Battery iPhone Battery and Performance Settings > Battery > Battery Health Maximizing Battery Life and Lifespan