we dont need no stinking fuses!

 

Most cars, I just drive it until it dies or at least shows signs of imminent death, but I'm rather paranoid with my 986, what with not being able to open the hood to even jump-start. (Yeah, I know about the terminal block.)

My OEM battery made it about 5 years, but was clearly near the end-of-life. Properly charged, the batteries should sit 12.5-12.7V or so, up to 13V if you check right after charging. Never below 12.5V for any length of time, as that will cause sulfation to form. I knew my battery was old and checked it regularly, watching it drop steadily; after it started dipping into the 11.xV range after just 3 days of not driving, I knew it was time to stop waiting, and yanked it.

There are better ways of checking battery health that will catch more modes of failure, but you unfortunately need some special tools to do it.