Feeling paranoid that I am placing batteries in metal cases I have decided to insulate the inside of all the metal boxes. Even though the voltage cable connection points are covered with rubber boots and no metal is exposed the inside of the controller (pictured) has been coated with heat resistant high temperature polyimide tape to avoid any hard shorts. The inside of the battery box has also been lined with 1mm thick heat resistant PTFE sheet, corner sealed with polymide tape. Basically if there are any circuit issues it won’t be because of the metal cases.

Edit: I had a chat with Ian Goodman, EV guru, on a FB post and he suggested that Mylar is an adeal material for insulation because it is more puncture resistant. I have used Mylar in the university design studios, but for tape drawing. .. and yes I can see how this material would be much more durable as we use surgical scalpels on it to cut tape. I think I will experiment with it. Using it on the top and half side surfaces of the inside of the controller to double insulate the contact areas for a second level of assurance.