With a few hundred or more power cycles, my Garmin Edge 800 wasn't holding much charge anymore. 5-7hrs at the most from an original 15hrs when new. Here's the process I went through to replace the battery with a third party replacement and the resulting battery life with the new battery installed.

Links:
Garmin Edge 800 Battery Kit (Amazon US): http://amzn.to/2oInIkU
Garmin Edge 810 Battery Kit (Amazon US): http://amzn.to/2qd5V6c
Garmin Edge 500 Battery Kit (Amazon US): http://amzn.to/2q5DMlk
Garmin Edge 510 Battery Kit (Amazon US): http://amzn.to/2oIzf3v


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