Hello. I am planning a bicycle trip through Europe, sleeping in the wild. I only want to use GPS for tracking my route (Strava app), thats all I need, I will check my e-mails and messages only once a while, otherwise I will have airplane mode constantly on to save battery.

What I need from you are some recommendations on how to get the most of the battery. As I already mentioned, the GPS will be on for some 12 hours every day, but that is all I need, no cellular, no Wi-Fi. How about Android versions? Which ROM was the most battery efficient? How to make sure nothing useless is running in the background? I sure will take a big powerbank with me, but I only want to recharge it if really necessary. Thank you for your suggestions

Airplane mode will help a lot. Maybe also delete or freeze all apps that you don't need. Disable screen brightness automatic, turn the screen as dark as possible and try to keep the screen off as much as possible. GPS will of course need much power. Some navigation apps use GPS over google play services that could save energy. Be sure that gps will turn off if you turn the screen off.