That guide didn't start as a Facebook post.

After that night, I wasn't looking for another piece of equipment. I was trying to understand the mistake I had made before my family ever needed me. The guide itself was simple enough — which battery, in what order, wired which way. No invention in it, just storage done right. What I didn't think to ask, not for a while, was where a stranger in an off-grid group had gotten something that specific in the first place. Turns out that's a longer story than a comment section.