Dead Battery - No Warning
 

I keep my battery on a tender all of the time, even if it's for a day or two. My Interstate was 9 years old. Okay, so I was pushing it. But, every time I started her up the engine spun right over. Last week I went for a drive and stopped at a store. When I came out the battery was totally dead. No warning whatsoever. I called USAA roadside and the guy asked if I had jumper cables. I was temped to say, "Yeah, but I'm too stupid to use them." I didn't. He said he'd be there in an hour or so. Since it's a standard transmission, I grabbed a couple of kids in the parking lot and had them push the car so I could bump start it. Got it home. Changed the battery. Checked the charging system. All's okay.
Moral of the story: Don't trust your battery just because it starts in the garage when you've had a battery tender on it.

I've read the life expectancy a your car battery is typically between four to six years, so yeah you were pushing it pretty far at nine! :)

Couple of months ago I went for a drive, stopped at a store, and when I came out the key just turned in the ignition without doing anything. Knew immediately it was something up with the switch, but I'd only changed it about 6 months before. Called the NRMA and waited an hour for a guy to come, he just zip tied it back in place. When I got home I checked and the tiny screws had come lose enough to let it fall out. Moral of story, when you replace the ignition switch, tighten the damn screws properly!

9 years has to be a world's record......

Batteries are a very weak point in the electrical system....

My battery...
 

....was only two years old. After an hour drive, stopped for gas. Go to leave, dead battery.

No warning. Jump start her, drive about thirty miles, BAM!--alternator light comes on.

My alternator went bad, BEFORE the car told me it was bad.

Get your alternator checked for some CYA.

Also, FWIW, my OEM battery in my 1993 Miata lasted nine years.

AGM bats rule.

My Interstate is getting up there too, my car is 14 years old, I've had it since new and this battery replaced the original when that one was 6 or 7 years old. It gets connected to my CTEK whenever I park t in the garage, even for 1 night. I expect this will be happening to me too at some point. Interstate does make a great battery for everyday use!

This thread is also a good segue into trickle charging. I use a tender over the winter, but I've actually heard that longer battery life can be achieved by allowing the charge to fully disapate (dead battery) before recharging. I have seen benefits to this theory in power tools, but then again they are either NiCd or Lithium. Is there an electrical engineer here that can put this to rest?

Had exact same experience. Drove 60 miles to visit my daughter. We went over to store, came out dead battery.
Someone offer to jump start me (I carry jumper cables) and off I went. Had to jump start to come home the 60 miles in the dark with head lights on. Good thing my alternator was strong

I now display battery voltage with my Torque app on my phone. Shows sitting voltage and running voltage. That would have told me my battery was on the way out as well as the state of my alternator

No, lead acid batteries lose capacity every time they are fully discharged. IIRC it's the NiCd and NiMH batteries that had a "memory".

The Interstate that came in my 986 when I bought it lasted 7+ years. It died with almost no warning. I had trouble starting the car once, and drove straight to an auto parts store to have the battery tested.

The CTEK maintainer I have does something called “desulfating” which is supposed to make the battery last longer. Every once in a while I see the orange light blinking while the green light is lit. I’m not an engineer, but I read it in the instructions-they wouldn’t lie, would they?

I'm not sure why but its very common for a battery to fail all at once. They work fine right up to the moment that they don't! Often there is no warning such as the classic "slow engine turn over on a cold morning". Thus, I replace batteries based on date rather than function.

Even an AGM battery can fail suddenly. I had a 5 year old one fail after highway driving for 2 hours. Stopped for gas, then moved it to a parking spot and went inside. 5 minutes later it wouldn't start. Jumped it and drove another 400 miles with multiple starts and stops and then it failed in my garage. Replaced it.