Even when they are new and fully charged, they have always cranked on first hit to TDC and stopped. Then hit it again and they'd start the airplane. Over the span of time I've had to have my starter rebuilt twice. Freshly charged.. when I hit the master on my volt gauge has always been slow working it's way to sweep up to 12 volts. Some days I even tapped on the glass....
I almost bought a new battery AND a "field" starter vs the permanent magnet Skytec I've had all these years, but Walter Klatt said try the battery first.
Finally got an above -10C day and some sun today to make it work friendly in the hangar. I installed an Odyssey PC925 today.. and the difference is like night and a BRIGHT day! I could taxi on the windmill effect alone and this was the battery right out of the box and already 5 months old. I checked it and it was only about 80% charged and figured I'd start there. On hitting the master switch the volt gauge snaps to attention now... and the cranking speaks for itself!
The old Gill Battery.. darn near dead albeit.
http://youtu.be/d6Tc1jWTZC0
The new Odyssey PC925 at about 80% charge.
http://youtu.be/e7MvQE1-MVM