I bought my Edge 800 about 10 years ago. It'll still go almost 10 hours while doing turn-by-turn on a course and the 820 is supposed to have longer life. I don't use Bluetooth or have a PM, just an ANT+ HRM. I have the backlight turned down about 2/3 and its timeout set to 30 seconds, data recording set to Smart. I only plug in a battery for ride of 150 miles or so.
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