Oh, and to add another design hint. Closely related to "always fuse off cells or packs as close to the batteries as possible" - make sure that you cover bus bars, terminals, wire solders and the likes wherever possible. The classic in small form factor is Kapton tape or heat shrink tubing, for anything larger go for voltage-rated plexiglass.
And for heavens sake if you're in small form factor and you got a battery... please just don't go and solder the ruddy wires onto the PCB directly. Use any cheap-ass connector you like.
Many a thing and occasionally even a life got destroyed by someone accidentally dropping a screw or a tool onto a live busbar. A wrench shorting out even a "plain" 230V circuit but right at the exit poles of a megawatt scale transformer makes for quite the firework.
And for heavens sake if you're in small form factor and you got a battery... please just don't go and solder the ruddy wires onto the PCB directly. Use any cheap-ass connector you like.
Many a thing and occasionally even a life got destroyed by someone accidentally dropping a screw or a tool onto a live busbar. A wrench shorting out even a "plain" 230V circuit but right at the exit poles of a megawatt scale transformer makes for quite the firework.