I reckon the battery is the least of your concerns tbh. If it dies it dies, easy fix.
It's the fluids in the car that can cause you issues if not factored properly
Is there an option for a friend to take it for a spin once a week?
If not, I'd be hesitant in leaving a car just sitting there for 5 months with no prep.
Also, I wouldnt worry too much about the oil for only 5 months... that can easily be changed on return without issues, but the other fluids are much more concerning.
Fuel goes stale surprisingly quick, so before you leave make sure there is jack all fuel in the fuel tank... that way there wont be much to drain later if theres issues.
When you get back, fill the tank at home using a jerry can so you dilute the stale fuel with the fresh fuel.
I'd also be worried about having the car sitting there and the coolant/coolant pump not being circulated. But 5 months should be ok. Any longer and I'd seriously be considering draining all fluids.
And if the car isnt going to be moved in months, jack it up. It's not just the tyres you need to be worried about, its the bearings.
You'll save a lot of hassles if you can get someone to take it for a 30min drive every week or so while away. Just so you can get it to operating temp and have all the fluids circulating.