this is a story about an over engineered solution plagued by feature creeping that had a happy ending.
I own a surface Pro 4 which is a great computer except on two point : Battery life and shock resistance. Here came my idea to fit a battery in an old suitcase to protect my computer and have extra battery life. then the project grew bigger...
I decided to add a raspberry pi running openVPN and a 4G modem plus a 2TB hdd to have my own cloud in a suit case with a solar panel because why not.
but this solutions proved impritical and i discovered that i could cobble up a simpler system for less money with the right component
time as elapsed since the last time. enough time that USB-C and power delivery are found in more and more device. I needed a beefier battery so that my old surface last a whole day and found the solution from an AliExpress battery case (https://fr.aliexpress.com/item/1005002352065127.html) that can contain up to 18650 battery. thats around 100 Wh of battery. this battery bank also boost the voltage to 12V via USB-C power delivery. From there I just had to find an adapter from surface proprietary connector to USB-C and here i go : surface proprietary connector to USB-C. Plus, i salvaged and tested the 18650 cell from old laptop to save myself the expense of buying new one.
and that's how I went from an overly complex suitcase that would have gotten me arrested in any airport to a few neats pack of battery that took less effort to assemble and use.