3 ms·fwiw i have a series 4 and i sleep in it every night. much better battery life than the first genby brandonscott 7y agofwiw i have a series 4 and i sleep in it every night. much better battery life than the first genmovedx 7y agoInteresting. I just keep reading the comments and sadly the ECG feature is not available in Australia and may never be as Apple have never applied for the licenses. Not a huge deal breaker but an annoying one.rikkus 7y agoWhen do you charge it?