On Mon, 8 Oct 2018 07:18:10 -0700 (PDT), wrote:

1) Make sure there is no current draw when the tractor is parked and switched off..

2) Buy a small charger to connect over the winter. But do not overcharge.
Maybe use a timer so it charges only an hour a day.

3) Buy a digital voltmeter.

A battery on long term trickle charge will last longest with about 13.6 Volts on it.

Any more and it will loose life due to over charge.
Any less and it will loose life due to undercharge.

m

Wise words! :-)