There is another problem.
Rust starts to build up (grow), and EXPAND. Only when you drive and press your brake pad, that helps to remove rust builds up on brake (and rotor). If you leave your car there for three months, the rust grows to the extend that car cannot move. You have to replace new brake pads and rotor.
When I am away for 3 weeks, I ask my relative to drive the car and for at least ten minutes, and do frequent brake stop (to sand away those rust built on brake pads).
As for battery, just disconnect it. It is easy to jump start the car and drive continuously for 30 minutes, the battery should be fully charged.
If you know how to change battery, disconnect is just a piece of cake.