Although the Apple Watch Series 2 offers better battery life than the first generation smartwatch, there are steps you can take to maximize the life of your battery and the lifespan of your Apple Watch.
First, avoid extreme temperatures. The Apple Watch is designed to perform well in a wide range of ambient temperatures, with 62° 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.
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.
Second, remove certain cases during charging. Charging your device when it’s inside certain styles of cases may generate excess heat, which can affect battery capacity. If you notice that your device gets hot when you charge it, take it out of its case first. For Apple Watch Edition models, make sure the cover of the magnetic charging case is off.
Third: store it half-charged when you’re storing it long term. Don’t fully charge or fully discharge the Apple Watch battery if you’re storing it for days. Instead, charge it to around 50%.