Stop start stopped working

[Lexman8]

Originally Posted by RoyMacDonald

The small battery is only for the electronics but if it isn't charged up enough the engine won't turn off even if there is enough power in the main battery otherwise you would lose all the electronic components as though the car was switched off altogether and it would not know when to turn on again. Short runs will not allow the small battery to balance charge to drain I think.

Roy

That's my understanding of it too.

[nu11eaf]

Originally Posted by RoyMacDonald

The small battery is only for the electronics but if it isn't charged up enough the engine won't turn off even if there is enough power in the main battery otherwise you would lose all the electronic components as though the car was switched off altogether and it would not know when to turn on again. Short runs will not allow the small battery to balance charge to drain I think.

Roy

Yes agree thats what I am trying to say too, sorry if I did not explain this properly, if the small battery has not enough charge the stop start will not cut in, its the small battery that initiates the stop start.

[RoyMacDonald]

Originally Posted by nu11eaf

Yes agree thats what I am trying to say too, sorry if I did not explain this properly, if the small battery has not enough charge the stop start will not cut in, its the small battery that initiates the stop start.

Think of the car as a computer and if the car's computer looks at all the conditions it needs to run stop/start successfully and does not find them it waits until the conditions for successful stop/start are met. The software program it runs tells it not to attempt to run stop/start unless the charge levels of both batteries are above certain levels to ensure the car never turns off and is unable to start again.

Roy

[grmsupra]

Hi
I had the same problem and now my start stop works so I thought I'd add my experience to this thread.

To cut a long story short, I bought the car from a dealer and assume it must have been standing for a few weeks, so the battery charge would have been low. I noticed that when I sat in the car and the "standby" ignition was still on, after a while a message came up 'low battery charge'. The battery had no problem starting the car and seemed fine. So I decided to give the battery a good charge with an external battery charger. After a good 12 hours I tried the car and the start stop began working. This lasted about a week and then stopped working again. I charged it again with a battery charger and this time it went a little longer. After about 4 cycles of charging the Start Stop has not played up again since.

Whether the charging reconditioned the battery in some way or some sort of software recalibration went on I don't know. However this must be worth a try before buying a new battery or a dealer visit.

[James77]

Had my car since 21/12, SS worked perfectly for 3 or so weeks then stopped working. I had done c800 miles all around town short trips, my trip to work is a 10 mile round trip. Perfect for the T5!

Went on a 150 mile round trip this weekend and the SS started working again and has done so for the last few days.

So I conclude it works just my style of driving is not conducive to on-going SS.

I suspect it'll pack up again soon until I venture out on another long journey.

[Driver Dave]

This has been an on going problem with these cars.
Unless you are doing a reasonable mileage each trip the S/S soon stops working and it takes a long trip to get it back again. If you charge the car externally it will work OK for a while but short trips soon stop it again. The manual is less than useless stating that a 15 minute run each week will keep it topped-up enough, not on my car it doesn't.
The only conclusion I have come to is that the battery and charging system fitted by Volvo is not fit for this purpose. At one time I even kept a record if the journeys I had done: mileage, time, external temperature, whether heated seats steering wheel and screens are on or not. I gave this to my dealer and sent it to Volvo UK but have never been given a satisfactory reason for the poor S/S performance.

[nu11eaf]

I have my battery replaced under warranty and S/S has been ok ever since. It never worked before unless I charged the battery with my c-tec charger, then only for a very short period.

[ergonomist]

Originally Posted by nu11eaf

I have my battery replaced under warranty and S/S has been ok ever since.

Ditto. SS was OK for a while, when I was making a lot of longish journeys, but then stopped working. Took many visits before dealer agreed there was a battery fault (about 3 months ago) and changed it. It's been fine since - even though I am mostly making short journeys at the moment (rarely more than 5 miles). Still occasional times when not all the parameters are met - but different circumstances each time (cold, or aircon working hard, or steering input, etc etc).

[elie63]

Hi,
I bought a new 2019 XC90 T5 last month, and stop/start (s/s) function did not work from day one of delivery.

I reported the issue to the local volvo distributor, however he mentioned that s/s function is successfully tested during the car preparation.

So I had to work by elimination, stopping/starting each features. and I discovered that ounce you stop the "Active Bending Lights" the s/s works normally and smoothly.

Please verify the case with your cars.

[RochdalePioneers]

Bought my S90 at the beginning of Feb, it was a pre-reg from the end of September which had been a showroom demo for 4 months.

Stop Start worked normally for a few weeks. Then stopped working completely. Then would stop once then refuse to do so for the rest of the trip. Then today abruptly started working normally - after I manually switched the engine off at a set of traffic lights...

I have had a few other intermittent software bugs and I'm wondering of this is another one of them. Car is being driven! 3k miles a month so even if the battery was low it should have been recharged fully after so many motorway miles.

Will try and switch off the cornering lights as suggested above!