auto hold and stop/start (again?)

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dnyoung607
Posts: 12
Joined: Wed Apr 01, 2020 2:03 pm

Post by dnyoung607 »

My stop/start worked for about 1 year (2019 XC 40). It ceased working in March, beginning of Covid. Has worked only rarely since then. Maybe bttery issue, but will report it again to dealer. Had the software update last January.

Hans Antoes
Posts: 14
Joined: Tue Dec 01, 2020 10:41 am

Post by Hans Antoes »

dnyoung607 wrote: Tue Dec 01, 2020 3:37 pm My stop/start worked for about 1 year (2019 XC 40). It ceased working in March, beginning of Covid. Has worked only rarely since then. Maybe bttery issue, but will report it again to dealer. Had the software update last January.
It's just a matter of low mileage/short runs. Do a few longer runs (say 30miles plus) and all will be ok.
Perky
Posts: 66
Joined: Wed Oct 30, 2019 11:41 pm

Post by Perky »

The battery for the stop/start is much smaller and of lower capacity. It doesn't take much to deplete it and not much to recharge it again. About 3-4 hours of the engine running (try to drive around a bit, not just standing still) will charge it up.
T4 AWD Oct 2019
Hans Antoes
Posts: 14
Joined: Tue Dec 01, 2020 10:41 am

Post by Hans Antoes »

Conventional petrol XC40s which have start/stop functionality have two batteries.

A STARTER battery of 12v 70Ah capacity which starts the car and covers most things, and a smaller SUPPORT battery of 12v 10Ah which supports the bigger battery in the start/stop function.

If the SUPPORT battery falls below a certain charge value then the start/stop won't work.

In my experience a couple or three 20 mile journeys will charge it up again.

There's nothing to worry about or report as a fault, just drive the car more. It's all in the manual.
Rifleman
Posts: 435
Joined: Wed Mar 21, 2018 2:21 pm
Location: Nottingham, UK

Post by Rifleman »

In my experience every trip needs to be >30-40 to maintain the charge on the support battery, short trips flatten it so quickly.

My stop/start function stopped working back in Jan/Feb this year. With one exception I have not done any journeys of more than 40 miles since then, avg journey probably about 15 miles.

Between lockdowns I made a trip of about 150 miles from Nottingham to Whitby. During a couple of short sightseeing trips there (about 60 miles each) the stop/start sprang into life and worked fine. Next two sightseeing trips it stopped working again. After the return trip home (Begining of October) it again worked for a couple of short shopping trips but since then nothing.

The car was serviced mid October and the dealer checked the condition of the support battery and reported that it was fine and holding charge as it should. They said I just needed to perform longer trips but also said that they have had many reports of this since the first lockdown began...
XC40 | First Edition | 2.0 D4 AWD | Bursting Blue | 19" wheels | Ordered 11/03/18 | Delivered 19th October 2018.
DanishPastry
Posts: 134
Joined: Mon Sep 14, 2020 4:07 pm
Location: West London

Post by DanishPastry »

Firstly, thanks @Hans for explaining the Support Battery. I didn't know such a thing existed (but have now read about it).

I don't understand why a second battery is needed. I'm not aware of having one on any previous car with Start/Stop. I simply can't think what possible benefit it can have.

The manual says, "When the capacity of the battery [but which battery are they talking about] has fallen below the lowest permissible level then the Start/stop function is disengaged."
Does that simply mean the engine will no longer stop running when the car stops (e.g. at traffic lights)?

The manual goes on to say, "Temporarily reduced Start/stop function due to high current take-off means: • The engine auto-starts without the driver lifting his/her foot from the foot brake pedal."

That I don't understand. What is 'high current take-off'? If the battery is struggling for capacity, you'd think it simply wouldn't STOP the engine in the first place, rather than re-starting it unexpectedly.
MY2020 R-Design
Chris John
Posts: 496
Joined: Mon Jul 20, 2020 9:08 pm

Post by Chris John »

I guess it depends how long you are stopped for and the current draw.
Air con on in the summer and car stopped for a while will restart the car, my Merc was exactly the same although it only had one battery.
I think some cars (not sure though) dont use the starter motor to restart and use a spring mechanism which is tensioned when the car is started.
I’ve never worried about it. If it’s available it works and I can see when it’s available by the icon
Volvo XC40 T5 R-Drive Pro. Thunder Grey with lots of extras
Hans Neesantoes
Posts: 6
Joined: Thu Dec 03, 2020 9:25 am

Post by Hans Neesantoes »

DanishPastry wrote: Wed Dec 02, 2020 10:55 pm Firstly, thanks @Hans for explaining the Support Battery. I didn't know such a thing existed (but have now read about it).

I don't understand why a second battery is needed. I'm not aware of having one on any previous car with Start/Stop. I simply can't think what possible benefit it can have.

The manual says, "When the capacity of the battery [but which battery are they talking about] has fallen below the lowest permissible level then the Start/stop function is disengaged."
Does that simply mean the engine will no longer stop running when the car stops (e.g. at traffic lights)?

The manual goes on to say, "Temporarily reduced Start/stop function due to high current take-off means: • The engine auto-starts without the driver lifting his/her foot from the foot brake pedal."

That I don't understand. What is 'high current take-off'? If the battery is struggling for capacity, you'd think it simply wouldn't STOP the engine in the first place, rather than re-starting it unexpectedly.
First point - If the smaller support battery is undercharged to start with (forgive the pun) then the start/stop function is disengaged - it WON'T work. The icon on the dash will indicate that the start/stop won't activate.

Second point - If the support battery is sufficiently charged then the start/stop function WILL work. However if you stop the car, let's say at traffic lights, then overload the support battery by using AC, fast fan, wipers, headlights, screen demister etc. then the system is clever enough to temporarily disengage the stop/start function restarting the engine so that the engine can then supply the necessary power to the high current use.

The support battery supplies the car's electrics when the engine is stopped. If you are using too much electric when stopped at the lights the support battery can't support this load so the engine needs to kick in.
Skyrimmer
Posts: 248
Joined: Fri Jun 07, 2019 3:14 pm
Location: Norfolk

Post by Skyrimmer »

My start/stop worked on a few occasions in the first year but this year it has not come on at all even after a 4 hour non stop journey from Norwich to Bakewell or after the same trip back. But as I nearly always turn it off it does not really matter to me.
XC40 Bright Silver T3 Momentum pro with just about every option plus mud flaps and sunglasses holder.
Hans Neesantoes
Posts: 6
Joined: Thu Dec 03, 2020 9:25 am

Post by Hans Neesantoes »

deleted post
- excessive use of smiley emoji
Last edited by Hans Neesantoes on Thu Dec 03, 2020 2:47 pm, edited 1 time in total.
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