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From the WA Electrical (Licensing) Regulations 1991-

regulation 4A (1A) - 'However electrical work does not include work on components
of the propulsion system of a motor vehicle, as defined in the
Road Traffic (Administration) Act 2008 section 4, that is
propelled wholly or partly by electricity.'

Also, apart from the risk of shock or electrocution from batteries and generators, there is also the risk of burns from fault current producing an arc blast which can also be lethal.

Test for zero volts before you touch and all that, but be aware that batteries that are charged are by definition not isolated, and cannot be considered isolated until they are discharged - insulating the terminals is not isolation.