Battery question

Cornersteady

Ok I've read all the posts on solar panels and I was just wondering if anyone can answer the following question. In my last van, we had a mover but the storage chaps used to help pull the caravan out and hitch up, I assumed the battery would be charging
as we drove to the site as the mover always worked when we got there, and we did this for 10 years

Now we have a new van fitted with a tracker so I need to keep the battery in a charged condition, so how long will the battery last just keeping the tracker going? We usually go away every two weeks in the summer, monthly September to November. but from
Decemeber to February not at all, will the battery last this time or do I need to fit a solar panel? Hope someone can help