Electricity is dangerous, potentially fatal, and our EVs are no different. Safety should be of paramount importance when working on your EV especially on the high voltage pack. Other dangers include the Hydrogen gas released during Lead Acid charging being ignited by arcs/sparking and battery acid spills due to shorted/overcharged batteries.
Some key safety principles are:
Always disconnect the pack and charger when working on your EV.
Make sure your high voltage pack is isolated from the Chassis
Wrap the handles of Metal tools with some form of insulation (eg. heat shrink, tape, tubing) so that they do not short across battery terminals if dropped.
When touching Battery terminals it is best to do so with one hand in your pocket or behind your back so that you do not touch both + and -, and so that the circuit cannot be completed across your chest (heart).
A rubber mat should be placed across the batteries which aren't being worked on to minimize risk.
Keep the most positive and most negative battery terminals as far away from each other as possible to minimize the risk of shorting out.