Have just replaced ours and about the same age of battery. All tests showed it was fine, but just leaving the lights on for 10 minutes caused it not to to start.  Didn't last as long as batteries in previous vehicles though. Also got a battery for far cheaper installed, than what the dealer charges, the markup has to be huge.

richms:

 

shk292: I was quoted around $900 for a replacement battery in a 5 year old diesel Passat the first time I had it serviced, apparently it needed changing. 2 years later having ignored this advice, it was still working perfectly.

 

If you're lucky it will decide to disable the stop/start by itself when it thinks batteries are dying. Saves buying the hardware mod to make it disable everytime. 

 

This is exactly what mine did post-lockdown: iStop and i-ELOOP stopped working when I went back to using the car after weeks of no use, and I was slow to cotton on as to why this was happening. In the end, though, a few long trips were enough to restore the function, and I learnt in later ones to at least run the motor for a bit.

The current signs of needing a new battery at some point are a hesitation when starting the car, but this has been the case for most of this year and it's still hanging on.

jonathan18:

 

That's twice the life I got from the battery for my own Mazda, and your replacement was still an absolute bargain compared to the $540 I would have had to have paid the dealer (or $1160 from Repco) a few years back!

 

Luckily, a GZ member came to the rescue and I got it at a far more reasonable price through him (thanks again @jeffnz). Annoyingly, it looks like that one is on the way out too (really didn't like being ignored during the Covid lockdowns), and I may well have to replace it even though I'll be selling the car in the next few months...

 

If you have a charger throw it on overnight. You'll likely get another six months.

richms:

 

If you're lucky it will decide to disable the stop/start by itself when it thinks batteries are dying. Saves buying the hardware mod to make it disable everytime. 

 

Now someone else's problem - a combination of maintenance costs, niggling faults and a few quirks with the driveability caused me to sell it. Probably the last VW I'll own.

I had a Panasonic OEM battery on my Lexus GS that lasted 11 years and it was still cranking, but I swapped it out as a preemptive maintenance.

The Panasonic OEM battery in my Lexus ES is 6 years old, and is still measuring well over 12.5 volts overnight.

However, the Panasonic OEM batter in my Lexus RX only lasted 6 years before voltage became <12V so I had to replace it.

Car batteries are a funny thing. I've certainly seen them last out to 10 years but they're much less able to tolerate full discharge once they're a bit older. Meaning that time you leave your lights on or the door ajar, is much more likely to finally wipe the thing out.

My last replacement was 8 years ago. Car starts first time, every time, except for twice in the last 6 months... one where i'd sat parked with my lights going for some time the previous day, and did so again for 10 minutes the next day (and it was only the latter time that the car wouldn't turn over).  Jumper-box assistance and then keeping it running for about 45 minutes 'propped up' the battery again after that.

Second episode was leaving my hazard lights running at an emergency scene for about an hour. Jumper-box came out again, then left it to idle for a while... again propped up, and is now acting normally (no issues). But i'm half expecting that if I let the battery sink to dead again, it'll just about be replacement time I think.  Officially they're good for 3-5 years, but over 8 years is entirely possible... chances of survival will reflect consistent temperatures and consistently keeping it at a decent charge level.

They do fail mechanically from time to time, I had one literally die (went open-circuit, killing my car engine) when I was about 200km from home once. Fortunately I was able to coast into a SuperCheap parking lot and pick up a replacement then-and-there. :)

The AA battery in our ancient Honda Fit died when my wife accidentally left the headlights on for 10 minutes whilst picking up the dogs from kennels last week. I had a Toyota Alphard Hybrid for a while and the 12v battery on that was very unreliable - it died once just because the interior light was on for a couple of hours. 

Those stop/start systems are a bit irritating and must play havoc with battery life etc. My Mercedes has it and if it activates one too many times such that it irritates me too much I just turn it off.

My battery - 14 years old when I posted this - is now 16 years old...

Sidestep:

 

My battery - 14 years old when I posted this - is now 16 years old...

 

That is a spectacular run!!!!!