I have a 12 volt battery in a walk behind tractor. It is a small lawn mower type battery that was bought last november and installed in a david Bradley walk behind tractor with an 8 hp electric start motor. It worked fine when it was installed. It had sat for about 3 months and then the cover blew off of it and it rained for several days so it got soaked. I went out to start it a few days ago and the starter was spinning but not engaging. I discovered the starter was turning backwards. the battery was almost fully charged. when I put a meter on it ( I used several meters) the polarity was reversed. In all my yrs of tinkering with cars and stuff I have never seen this happen. So what do you all think? What is happening here?