I rarely drive my Z, and as ARA300ZX pointed out, once a redtop is dead, its dead. I took mine to the Interstate store (I guess they manufacture the redtop/own optima?), and they gave me a brand new redtop after testing my old one and determining it was dead. They did say however this would be the last time they would replace the battery for me because of how many times they have already replaced it. I just purchased one of these and would suggest you do the same:
