Hello All...
Having gone through a failed i-Stop battery, it would be advisable at this point to stick with the OEM unit. My Dealer initially replaced the failed battery with a non-OEM one (as instructed by Head Office) only to find the i-Stop system would not set itself up and calibrate to the new battery.
Needless to say, they ended up fitting an OEM battery, and all is Zen with the world..!!!
One would hope you are correct xtrailman. If a standard $100 battery last 4+ years, how do you figure a battery is free at 4.5 years? If I remember correctly, CATs were terrible until the government mandate, that they last 80K miles.