not sure why you worried.
if the bat is hooked up.. you know wiring tolerates bat voltage.
always hook bats matching charger polarity to bat polarity.
on some very, very old chargers I have seen units that had a metal case that was actually tied to the negative polarity for some reason. it's rare.. but if you are getting sparks from charger case to tractor chassis.. insulate it with some cardboard.. etc.
again.. it's rare..