If a hired «professional» connects a charging apparatus with reversed polarity, I would suggest that the customer should be entitled to have his vehicle inspected for electrical damage by a mechanic of his choosing, with the hired professional being responsible for the actual cost of his inspection or a typical mechanic's cost, whichever is less,
along with the cost of repairing any electrical
faults that are
discovered and for which the reverse connection would be the lost likely cause.