Airplanes, like automobiles, require a battery. All batteries wear out eventually. I had to replace it today. They are easy to find, all you need is $300 and you can take it home right away. This particular battery is a Concorde RG-25XC. It is a sealed battery so the acid can't leak out. In the old days, you had to use a lead acid battery that was not sealed. It had caps on the cells to vent them and they were not supposed to leak. Of course they did and you ended up with a corroded battery box. Every annual it seemed that I was repairing that stupid battery box. I don't miss that part of the past at all.