Preconditioning issues - Low battery warning

[KNVXC90]

Originally Posted by nu11eaf

Must be my battery then as ss works ok after charging up, I know there is a support battery capacity % were the ss does not work as my dealer service dept lowered my % setting and said it was set too high and ss would not work if battery dropped below that, think it was set for 80% capacity before they lowered it. SS only lasted a a week or two after getting it back.

If the software updates are not fixing it, worth pushing for a new battery.

[nu11eaf]

Originally Posted by KNVXC90

If the software updates are not fixing it, worth pushing for a new battery.

I will when next in dealers, I am used to not having ss now as it has hardly ever worked for long.

[Driver Dave]

The Stop/Start on my car has been fine over the summer but now, with the colder weather, it only works when it wants to. I think it is the way the software controls the alternator/battery. As soon as I need to use the electric seat heaters and heated wheel S/S fails to work.

I find this ridiculous as the seats and wheel only come on when the engine is running and the alternator should be providing the power to keep the battery level up. The start/stop system is, I believe, also part of the emissions control for the car, that's why it always reverts to "comfort" mode when ever the engine is re started.

A car designed in Sweden that you can't use the cold weather "comforts" with out standard functions of the car failing - you couldn't make it up!

[Jcbrown]

Originally Posted by mrlossyman

It seems the battery isn't the issue.... However start stop never works...

When I first got this S90, SS never kicked in, and READY light never came on.

Took 4-5 months of investigation and trails: fully charge battery would sort it for a day-or-two; Full CANbus s/w update would sort it for a day or two; New battery would sort it for a day or two. But after the day-or-two, it would always cease to work.

In the end it was allegedly tracked down to a s/w problem. Apparently the s/w kept thinking the fan was going, when it was not, and therefore would not allow the SS to engage.

Quite how a full charge or new battery would sort the issue for those few days and why it didn't affect all cars beats me. But the explanation I was given was s/w, and it was another full CANbus update before it was sorted

[mrlossyman]

Now this is odd.

Just walked and dropped my kids off at school and was reading these posts on the way home. Since precon worked manually yesterday I thought I'd just try it by the app one last time. Hey presto when I got back to the car it was on and no warnings. What is strange is since the low battery warning yesterday I've only done short trips so it can't have been a charge issue. I'm so used to SS never working I'm not too worried about that. I'm wondering if the manual precon has reset something in the system.. Strange old car the XC90.. thanks for the replies.

[exbmw]

Originally Posted by mrlossyman

Now this is odd.

Just walked and dropped my kids off at school and was reading these posts on the way home. Since precon worked manually yesterday I thought I'd just try it by the app one last time. Hey presto when I got back to the car it was on and no warnings. What is strange is since the low battery warning yesterday I've only done short trips so it can't have been a charge issue. I'm so used to SS never working I'm not too worried about that. I'm wondering if the manual precon has reset something in the system.. Strange old car the XC90.. thanks for the replies.

As I keep saying to Mrs.exbmw...."this car is brilliant when it works"

[Lexman8]

Originally Posted by mrlossyman

I'm now wondering if this is an app connectivity issue and would be grateful if someone could try starting precon by the app. I use android.

Precon from my Android app (and stop/start later on) both worked fine this morning even though the car has been seldom used since last Friday.

[Lexman8]

Originally Posted by nu11eaf

My starter battery starts car instantly no problem even after a period of none use and in very cold weather, the stop/start wont work if support battery is not above a certain level of charge. Now you have mentioned this I think my service manager said they had lowered that figure as it was set too high.

Looking at the list of conditions for stop/start to work it mentions the charge state of the starter battery but not the support battery.

The engine does not auto-stop in the following cases:

• The car has not reached approx. 10 km/h (6 mph) after starting.
• After a number of repeated auto stops, speed must again exceed approx. 10 km/h (6 mph) before the next auto stop.
• The driver has unfastened the seatbelt.
• The capacity of the starter battery is below the minimum permissible level.
• The engine is not at normal operating temperature.
• The ambient temperature is under -5 °C or above approx. 30 °C.
• the windscreen's electric heating is activated.
• The environment in the passenger compartment deviates from the set values.
• the car is reversed.
• The starter battery's temperature is below or above the permitted limit values.
• The driver makes sweeping steering wheel movements.
• The road is very steep.
• The bonnet is opened.
• When driving at high altitudes when the engine has not reached operating temperature.
• The ABS system has been activated.
• In the event of heavy braking (even without the ABS system having been activated).
• Many starts during a short period of time have activated the starter motor's thermal protection.
• The exhaust system's particulate filter is full.
• A trailer is connected electrically to the car’s electrical system.
• The gearbox is not at normal operating temperature.
• The gear selector is in ± position.

As to why the car starts instantly it's possible that even if the charge state of the starter battery is actually monitored for a normal start (and it may not be) it's possible (likely?) that it's set at a lower threshold than for stop/start because starting the car initially is a one-time event whereas stop/start is a frequent event and more likely to drain the battery. (I'm just thinking out loud )

[nu11eaf]

Originally Posted by Lexman8

Looking at the list of conditions for stop/start to work it mentions the charge state of the starter battery but not the support battery.

The engine does not auto-stop in the following cases:

• The car has not reached approx. 10 km/h (6 mph) after starting.
• After a number of repeated auto stops, speed must again exceed approx. 10 km/h (6 mph) before the next auto stop.
• The driver has unfastened the seatbelt.
• The capacity of the starter battery is below the minimum permissible level.
• The engine is not at normal operating temperature.
• The ambient temperature is under -5 °C or above approx. 30 °C.
• the windscreen's electric heating is activated.
• The environment in the passenger compartment deviates from the set values.
• the car is reversed.
• The starter battery's temperature is below or above the permitted limit values.
• The driver makes sweeping steering wheel movements.
• The road is very steep.
• The bonnet is opened.
• When driving at high altitudes when the engine has not reached operating temperature.
• The ABS system has been activated.
• In the event of heavy braking (even without the ABS system having been activated).
• Many starts during a short period of time have activated the starter motor's thermal protection.
• The exhaust system's particulate filter is full.
• A trailer is connected electrically to the car’s electrical system.
• The gearbox is not at normal operating temperature.
• The gear selector is in ± position.

As to why the car starts instantly it's possible that even if the charge state of the starter battery is actually monitored for a normal start (and it may not be) it's possible (likely?) that it's set at a lower threshold than for stop/start because starting the car initially is a one-time event whereas stop/start is a frequent event and more likely to drain the battery. (I'm just thinking out loud )

I may have mis-sunderstood the service manager when he told me had lowered the SS battery cut off point for stop start as it was set at a too higher % capacity. I thought he was talking about the small battery % capcity at the time, but thinking about it, the small battery should always be charged by the larger capacity starter battery, but I may be wrong there as well.

My main point earlier though was that some things on the car wont work if battery is below a certain level of charge and the original poster might try charging the battery and to see if pre-conditioning works better after charging, then got side tracked onto stop start, worth a try.

[Lexman8]

Originally Posted by nu11eaf

thinking about it, the small battery should always be charged by the larger capacity starter battery, but I may be wrong there as well.

I'd guess that the charge controller monitors the state of each battery separately to ensure that each gets the appropriate amount of charge as well as to prevent overcharging. As you said previously, the support battery is only 10Ah compared to the main battery's 80Ah so the smaller one should charge relatively quickly.

All things considered, and given my own experience of a sometimes seldom used car still working 'properly' for both precon and S/S, my speculation is that it's one of:

• the main battery is gubbed
• the charge controller is faulty
• there is a current drain somewhere
• the S/S threshold is still set too high
• something else