I use the Ctek battery charger. I hook it up directly to the battery and run the wires out of the trunk. I was worried about the trunk lid cutting the wires, but the sealing rubber leaves enough cushion so that has not been a problem. I normally hang the ctek from the wall behind the car.
I have used Seafoam as a gas stabilizer.
2008 Z4 3.0si Sport Package, Premium package, heated seats, M sport seats, xenon headlights
2002 325 xi, sport handling, rosewood trim
2005 X3 Premium package