Z4 goes into "sleep mode" when not driven for 5 days?

[PaperSniper]

My Z4 does not get driven often, perhaps once every 5-7 days. When it is driven, it is driven for a decent amount of time, perhaps 40 miles minimum. Surely enough to top off the battery?

This has happened several times in the 6 months I've owned the car. Bought it new. Has about 4.5k miles on it. My car has the feature where the doors unlock when I approach the car, and lock when I'm about 20 feet away:

Had a drive. All worked as it should.
Parked in my garage, nothing left "turned on"
Walked into the house and heard the doors lock and mirrors fold
Several days later....
Approach the car: It does NOT unlock the doors nor unfold the mirrors, nor are there any sounds or lights
Press 'unlock' on the fob. All works normally again.
If the car is driven again in a few days there are no issues. If longer than maybe 5 days, the process repeats

The first time it happened I thought I had a dead car battery, but that is apparently not the case. A dead battery in the fob is not likely since it works fine if the car has set for only a couple of days.

Weird, eh? :|

Doug

 

[enuff_zed]

I guess its going to b difficult to check the battery voltage at that point?

Just one small thing............I have been told by two different BMW salesmen that it is not a good idea to leave on the auto lights or auto wipers as they may put a slight drain on the battery. I'm not sure if this would happen in five days though?

 

[Johnbmwz4]

I have a Range Rover Sport that does the same. The car has park heating that warms the car up before you get in but if I don’t use the ca for 5 days it goes in sleep mode and I can’t use it. It also shuts other things down too. Once car is started all ok unless I leave for another 5 days. It’s to save battery life I believe.

 

[Anonymous]

Fairly standard battery self protection scheme..

Designed to ensure that when you eventually do return, maybe 60 days later there is enough juice to start the engine..

All that waiting for you to maybe turn up wireless stuff burns up a lot of juice over time!

 

[dr_john]

I often leave my G29 parked for 7 days, especially in the winter.

I don’t get any ‘sleep mode’ happening, maybe it’s a difference between UK and USA regulations and builds?

 

[raven]

Approach the car: It does NOT unlock the doors nor unfold the mirrors, nor are there any sounds or lights
Press 'unlock' on the fob. All works normally again.

i have the automatic opening of the mirrors turned off, but my car is currently only driven once a week and using the comfort access by touching the door handles works just fine each time. Maybe its only the proximity detection that gets turned off? Try just touching the backside of the doorhandle next time and see if the car unlocks

 

[Argyll Andy]

Not an answer but would this stop happening if it was hooked up to a CTEK or something similar?

 

[Anonymous]

Not an answer but would this stop happening if it was hooked up to a CTEK or something similar?

Depends whether the logic for shut down is driven by time left unused or amount of battery capacity remaining ..

Thats part of the reason with these modern cars you never plug the charger across the battery terminals as that circumvents the intelligent battery monitor (IBS) and then it can't work out when to panic and shut systems down pre-emptively..

 

[Argyll Andy]

Not an answer but would this stop happening if it was hooked up to a CTEK or something similar?

Depends whether the logic for shut down is driven by time left unused or amount of battery capacity remaining ..

Thats part of the reason with these modern cars you never plug the charger across the battery terminals as that circumvents the intelligent battery monitor (IBS) and then it can't work out when to panic and shut systems down pre-emptively..

I don’t have enough knowledge about how these things work as to what possibly triggers this. Just getting ahead of the game :wink:

 

[Anonymous]

A watchdog monitors the state of battery charge and selectively and progressively shuts systems down to ensure the likelyhood of a successful start..I recall its around 35% ish residual capacity and is ambient temperature related..so the colder it is the more charge it reserves..not simple..

 

[PaperSniper]

Update. I'm the OP.

The "genius person" at my BMW dealer said what I have experienced is normal. I don't recall exactly, but I think she said the fob ALSO goes into some sort of "sleep" mode. Not sure why if the battery is doing no work, but whatever.......