I totally second that wording and I do know what I'm doing.

This setup is only safe in a structure that doesn't have people or other stuff in it and that you are not going to be upset about if it burns down.

I wrote it that way because the hacker ethos here makes a lot of people assume they know more than they actually do about all things tech. It's easy to learn how batteries work and how to make big packs of cells but the practical and institutional knowledge required to do it safely is not something one should just "hack" into. That's why.