Kicking an old topic but no reason to start another.
Replaced the battery in the Ford GT. Consignment guy has been really good about keeping it on a tender and called today and said the tender had an alert state that it wasn't keeping up. Called Ford. No batteries. The manufacturer (Optima) is on backorder, could be months. Well, the Ford battery is just an Optima #25 so I called around town. All of the Optima places, Ford (if they had one) including Amazon, wanted the same price so I trundled over to O'Reilly's and picked one up.
I can't whine too badly. The battery lasted SEVEN! Yes, 7, years.
In retrospect I had a heads up that it was coming. When I took the car in for its annual emissions test, I noticed that the boost gauge wasn't working (a dreaded gauge failure?). After the test was done and I started it up again, the gauge was OK. So this was probably an early indicator that the battery was on its last leg.
I use the Cooltech battery tender config. That connects to the battery posts and leaves a tail under the hood area to make connection easy. So before pulling the battery I connected the Ford one to the power socket to (hopefully) keep all of the electronics powered. It worked! When I was done all of the emissions adaptives were still present so no drive cycle to reset for next year!