I have a 2008 Mini Cooper, garaged in Kansas, but am not there more than one month in three or four. I have it on a trickle charger, but what else should I be doing to maintain it?
You don’t need much else. You will be driving it for a whole month, make sure it gets a good workout. Keep up the regular maintenance.
A battery maintainer and driving it a few times a year (enough to use a couple of tanks of fuel) should be fine. If you don’t use a couple of tanks of fuel per year, then I would suggest adding a fuel stabilizer every time you leave. Us the instructions on the container.
Remember to read the owner’s manual it will list maintenance needed and you want to make sure all that maintenance is done. Some of the maintenance items will say something like "every 5,000 miles or once year. whichever comes first. Follow that advice.
Many cars, new and used, sit unsold on dealers lots for far longer than yours.
I’d focus on making sure you’re going through a new tank of gas/year, add fuel stabilizer to your gas, and use a battery tender/maintainer. Follow your owner’s manual for the rest.