Was coming back from a long run (just at the end of an hour long drive after two separate 45 minute drives) and enabled the stop/start system to see if it would function as it hadn't for a few weeks which I put down to the colder weather.

S/S engaged and the engine stopped but when I depressed the clutch it did one crank and then cut out. I knew S/S had failed so used the key to initate cranking where the car started pretty happily.

I tried it a couple more times once I got home. First time the car did start again when I pressed the clutch shortly after S/S stopped the engine. The second time the car failed to start after I let it sit off for a little while (roughly 10 seconds, not an excessive amount of time). The first compression when I went to start with the key sounded a bit sluggish but the engine fired up again with no problems. The lights and AC were on during all of this.

Got a warning on the centre screen of Start/Stop unavailable, start engine manually/manual start required. In the speedo the only warning I noticed was an oil light which makes sense since the engine wasn't running. I've not experienced this issue before.

I'm guessing battery is on its way out as it is 9 years old. Going to get a battery health check but wanted to check that there aren't other potential causes I don't know about

Fiesta mk7 1.0 ecoboost

And as of today S/S is working as expected with no issues, very strange. Still going to get a battery test but it makes me wonder if it was just a software issue that was fixed by restarting the car

Final reply, battery is ok at 89% state of charge so I can only assume it was a software issue. At least I'm not spending £100 on a new battery

Rejoice in the extra service life your engine is getting by Stop/Start not working

On 2/15/2026 at 7:12 PM, SomethingAsADisplayName said:

I'm guessing battery is on its way out as it is 9 years old

I would agree with that guess. They usually last around 3 to 4 years. I've already replaced the one on our 2019 Fiesta and the one on my 2022 Puma is getting near the end of it's life.

On 2/19/2026 at 9:08 AM, DaveT70 said:

Rejoice in the extra service life your engine is getting by Stop/Start not working

Yeah it spends most of its time disabled these days, I only enable it to check that it works which would indicate my battery is in good health

It's done very well to get to 9 years on an S/S car. A friend of of our has just had to replace the battery on her 4 year old MINI (AGM so not cheap).

My last Fiesta was still ok at 5 years, and the current one at 3, but I do a regular top up with a smart charger every 5/6 weeks and S/S is usually disabled by driving in Sport mode or the switch.

I would assume that as the battery is rated for S/S it is more durable than a regular battery so when you don't use S/S you can get ridiculous life out of it. My mates Fiesta battery lasted around 9 years who also disabled S/S most of the time (1.0 Ecoboost again)

A good chance there's died at an earlier age because of the ridiculously short journeys they used it for (literally a 2 minute commute to work)

Batteries are made to a lower quality nowadays. It's nothing to do with stop-start. They're just crap now. I doubt any battery fitted within the last 2 or 3 years will last anywhere near 10 years on any model.

44 minutes ago, TomsFocus said:

It's nothing to do with stop-start. They're just crap now.

Fair point! As we see from endless posts on here, S/S gives up the ghost anyway at the slightest excuse, so perhaps its more to do with the plethora of infotainment, connectivity, safety devices, cameras, sensors, keyless, fancy ambient lighting, blah blah, fitted these days, much of which is always "on" to some degree.

9 years still sounds pretty good for a relatively modern car. Until our current SEAT Mii (now at 12 years) our previous best was also just over 9 years, but that was a PSA XUD indirect injection diesel so more cranking load and glowplug use.

(I thought that was reasonable at the time, but looking back I wonder if I could have eked a bit more out of it with the more sophisticated Maypole/C-tek/NOCO chargers we're now all too familiar with on here.)

Even older, more basic, cars seem to be having more battery issues now. I am sure something changed with the materials used in manufacturing around the pandemic years.

Possibly for health reasons. (Although lead is a horrible metal to be working with anyway). But more likely due to a reduction in earnings, and higher living costs, driving a need for planned obsolescence. The same is easily visible in the quality of white goods and other household items produced now. Just a shame we can't 'see' inside a car battery to prove the same for those.