My Concorde battery was very good for ~5 years. I kept if for 7 years, but by the end it only had ~5 - 10 seconds of cranking capacity. (Luckily, "C" models start very easily.) The last time I was at Portland International (PDX), it died on the ramp. Very embarassing hand-propping my plane in the rain, parked next to all those jets, with their flight crews watching me from inside FlightCraft. BTW, I have a SkyTec starter, which spins the engine a lot faster than stock. With the standard starter, I would have replaced the battery a lot sooner.
