Battery, at last

So, that's three...

My MiL picked up her new Fiesta MHEV 3 weeks and four days ago. Loves it to bits. I had a shot of it on collection day, I was very impressed by the ride quality especially on 17" wheels and the ploughed fields that are Edinburgh roads these days.

She drove it on Saturday, went out today unlocked it, got in, no ignition. I've just got home, battery won't unlock the car now, blade and doors to manual to get in. Battery 5.16 volts. That's all three cars bought new since 2020 that have had dead 12v batteries now.

No lights left on outside or inside. Will check drain when I get this battery charged up again.

Starting to think keeping the relatively low tech, no OTA Volvo might be the smart move.

Not that I can get to the bottom of. The KIA I suspect was the result of an OTA but no one is admitting to, my Focus I suspect was the result of 13k Kms in two years, the bulk of which was two road trips over two or three weeks, though it got the same 12v boost once per month as my diesel Volvo.
I think I may have sussed the Fiesta issue, there is a bolt next to the fuse box which was only finger tight. I nipped that up and the dash cane back to life. The battery was still low, leaving that on a recondition charge then to test it out.

Well, don't I feel silly now, for writing that? The car's lifeless - wouldn't even open when I tried to take it to German last night. Since it had been fine on Saturday, I thought at first it was a keyfob battery problem, but when the other fob failed to unlock it this morning, I opened the driver's door with the mechanical key blade and found nothing happening within, the dashboard clock forlornly stopped at 9.20. We've had some ferocious rainfall since the weekend, so it's possible some stray water has added to an existing battery problem, but I think the thing has just come to the end of its life, at least in this car.

Not taking any more assurances from the AA that the battery is fine - although the output to the monitoring app still shows healthy voltages in the 13.0-14.5V range from Saturday's outing. I have a mobile fitter booked to supply a new one, although annoyingly not till Friday morning. That's a week before we go to Wales, so I just need it done this time.

Well, I wonder whether the old battery was below par even when I bought the car. The new one went in this morning, so I took the CLS out on my afternoon mission and drove it the long way home.

Observations: the green ECO symbol for stop-start took a while to come on — I don’t suppose the battery was quite full when it arrived — but once on, it stayed on, even after several stops in town traffic. That never happened with the old battery, even when it was only four years old. And when it did stop, it often restarted even before the lights had changed. This seems much better.
And the sub-80°C coolant temperature I’ve been complaining about hit a much healthier 85-90°C, according to the MB app, with the oil temperature reaching 98°C, which makes me wonder whether the old battery had even been supplying the sensors properly.

So the car seems happier, and should work better on the long trip next week. I should probably have had this done years ago. Given their fondness for spotting work that isn’t even there, I’m a little surprised the battery has never popped up as a comment when the car’s been in an MB workshop.

Presumably when running, a multimeter was showing 14V or more across the battery meaning the alternator was working. And when stopped the battery was showing less than 12V and even after running for a bit the voltage in the battery hadn't gone up much?

Can’t remember where/who fitted that new battery for you. Was it a garage or did you do it yourself?