I got tired of my battery dying on 3-day bivouacs, so I built a 100% offline phone. (Tutorial included)

I recently finished a 400km bikepacking trip in France right before the 40-degree heatwave hit. Currently bored and stuk near Le Mans (starting from lovely Perros-guirec) One recurring issue I had on previous trips was my phone draining its battery while searching for a signal in remote areas, or running out of juice during multi-day bivouacs.

​

​To fix this, I took a secondary Android phone and repurposed it into a dedicated offline device. I used ADB to strip out the bloatware and trackers, and loaded it exclusively with open-source apps via F-Droid. The device stays permanently in airplane mode. It holds offline topography maps through OsmAnd, the entirety of Wikipedia via Kiwix, offline survival guides, plus my music library and a manga reader for the evenings in the tent and video games (totaly legal lol) By keeping it entirely offline, the battery lasts significantly longer.

​

Like more than two days with OSM on for more than 7 hours a day (I think it's insanely good)

​

​I documented the whole process and made a step-by-step tutorial on my site so anyone can build their own. The URL is https://oraclemarin.fr/OffGridPhone/

​

​The guide is completely free. I am currently unemployed, so I did add an option on the site to prep and preload phones for people who are not comfortable with ADB commands or custom OS installations, but the main goal is just to share the DIY method.

​

​I attached a screen recording of the interface. I am curious to hear how you manage digital navigation and battery life on long stretches without power. Ha it's in french btw totaly legal music and games lol. Real legit stuff : offline wikipedia (all) wikihow (all) and Guttemberg library (Open source as well)

​

​