Just the electric clock in mine will run the battery down in a couple of weeks. I have an inexpensive battery minder that I bought from Harbor Freight that I hook up periodically.
I use some other ones that are better, but still only around $20 that will charge to peak, then go on maintain. I have these on a boat and a "classic" car that don't get used much. They have a pig tail that attaches to the battery with a plug that can disconnect about halfway to the charger. That allows you to leave it hooked to the battery, but connect and disconnect quickly. I have used this type for years on boats and cars and they really keep the battery in top shape.
Dale