I've read claims (theoretical and practical) from both sides, so apparently the safety of lithium cells can vary widely based on manufacture quality and maintenance.

But also, on the video, they shows each pack of cells he uses has individual over and underchange and temperature sensors, so the system is able to tell if any individual section is going bad. It's a pretty neat, and external installation, so I don't think it is very harmful on a "massive heat incident".

A properly designed lithium ion pack with tested high-quality cells is a very safe thing in the environmental conditions it was designed for.

Notice how many qualifiers are used in that statement.

BTW I've seen lithium cell safety bags, that can hold the flame enough. I wonder how a case could be done in a similar way to at least contain the heat and gas.

Also, could there be a thermoelectric powered fan to slow down the heat rise when cell(s) starts to fail or burn ?

You absolutely can design a firewall system able to fully contain a runaway pack. They have small systems that look like briefcases to nab runaway laptops on planes, for example. But when a cells goes, it goes. No fan is going to remove anywhere near enough heat. And you wouldn't want it to spread the vapors, as HF is a genuinely dangerous byproduct. The only real solution is full containment. And being 100% confident in your containment solution would require a lot of destructive testing- it isn't a trivial problem.

Ok a fan was ridiculous, but I didn't mean to diffuse gaseous products; just tap into the heat to activate some endothermic reaction around the system to, well, delay or dampen the process.

Thanks nonetheless for the return