Aircraft batteries have improved over the years. When I got my first airplane in 1976, the standard battery was a Gill lead acid battery. It had caps for the cells which were supposed to contain a valve to prevent acid from leaking. It turns out those things didn't work all that well, and we all faced battery box corrosion. I remember painting the inside with tar after washing them out with bicarbonate solution. It was always a maintenance pain. The battery of choice nowdays is a VRLA/AGM (valve regulated lead acid/absorbed glass mat) which is sealed preventing acid leakage. These buggers are expensive, over $200. You hate to screw one up. I decided this time around to spend a little time doing some more careful reading about maintaining these batteries. I started putting a charge on the Cessna battery today. They self discharge so after months of inactivity they need to be recharged. I got stuff all hooked up and let it start. Then I decided to shut it down and check up on the suggested procedure. I will keep you posted.