I have a John Deere LT155 mower. My son thought that the battery died so he used the battery charger to try and jump it. He cross connected the the cables and some wires started to melt. When I went out to work on the mower, It turned over very slowly....I hooked up the battery charger to the 40 amp setting and it attempted to start then the wires melted all the way through....I have no idea what could have happened
Do yourself a massive favour & buy the JD technical manual./
Have a couple of beers first if you find spending money a trauma.
It has a step by step fully illustrated electrical diagnosis & repair section.
Some of the 100 series have a fuseable link, which is designed to melt while others have fuses .
JD change their wiring more often than I change my undies