I'm getting back into model aeroplanes and this time electric-powered ones. They use lithium-based batteries extensively, and they are incredibly fussy about how they are charged & discharged initially, then under regular use and how far to discharge them, and the precautions needed when charging.
Check out Youtube, there's a bunch of videos of those batteries blowing up and catching on fire from excessive charge rates and so on.
You really have to be rather careful with them.