@Piet Unfortunately, there's a lot of FUD regarding LiFePO4, understandably brought about by the reputation of LiPO. In actuality, they're even safer than lead-acid. Worst-case failure conditions LiFePO4 mean venting toxic smoke (they don't heat up enough to catch fire). Worst-case for lead acid is exploding (H2 + O) and spraying H2SO4 around.

https://www.youtube.com/watch?v=aQs7L5LmEss

Regarding balancing in parallel, the voltage differential is low by their nature, and their charging limit is 3C-5C (600a-1000a). You'd need some impractically thick wires (and a battery so flat as to be already ruined) to get anywhere near that! It's too time-consuming to be practical for regular balancing, and more intended as a way to recover from fuck-ups.

I prefer a BMS because I'm lazy, but they're absolutely not a necessity, and there are plenty of people running fine without them :)

• and to make it clear, putting a <2.8v LiFePO4 battery in parallel with a tonne of others and no current limit is only a good idea if the alternative is holing on rocks because you can't get your engine started