What should be the typical battery drain on the AGM battery for Flying Spur 2014? I'm seeing continuous draw of approx. 3.56A when the car is off. I sense something is not right as my brand new batteries keep dying over a period of 2 days. It did get approx. 30-40 days of daily driving time on new batteries prior to that. I park it inside a temperature controlled room so the cold weather outside does not really play into the mix. Any help would be greatly appreciated. Thanks!


Bentley Flying Spur 2014 - Battery Draw

 

Hello @pupdogg ,
Do you have any other aftermarket equipment installed or plugged in, or even a phone charger or USB power port plugged into the cigarette lighter socket ?

I state this because I just had the same issue with my A8L W12, the A8's have a battery percentage of charge that you can pull up on the MMI screen, well I had my alternator go out after I had my exhaust system replaced, it of course included electrical welding, so after I replaced the 7 blown fuses and the alternator all was fine for a bit, then if I left the car for a few days she would be either dead or down to 5%, which the Audi system shuts every other system down to save that last bit for a one time start, you even have to use the physical key in the door, but if I drove everyday, no problem, but then I left it for 16 days in January, outside, and she fired right up, and had a full charge according to the MMI display, yet, 2 weeks later after sitting for 2 days it was back at 5%, so I was thinking "what did I do differently for those 16 days" and I came up with that I had removed the USB power port that was plugged into the cigarette socket, I was thinking that, that little tiny LED could not drain the battery, but I came to realize that it would not allow the vehicle to go into total sleep mode, therefore the console lights would be on, along with the tiny lights in the rear view mirror, so I believe that many other systems stay awake waiting for operation.

I tested this again by leaving it plugged in for just 1 day, and it was at 60%, then I drove for so many hours and had 100%, so then I made sure to shut everything off prior to shutting down and removed the USB port from the socket, well she sat for 4 cold windy nights and has 100% .

Johnny

 

I'd be interested to see what my car does, current wise, when switched off. Need a current probe with datalogging to do it though. That or shut myself in the boot for a while!

 

Hi Guys, sorry for the delay in my response. After banging my head against the wall for the last couple of weeks, I think I have finally isolated my problem down to the Rear Seat Entertainment (RSE) system. In my car, RSE consists of the following 4x fuses: #18: RSE 10A, #22: RSE BCU 5A, #23: LH DVD 5A, #24: RH DVD 5A. I could not get around to acquiring a proper data-logger but did have a voltmeter, a flashlight and a GoPro on hand to be able to monitor and document my issue. Attached you will find snapshots taken at 3 different time intervals of before and after removing the RSE related fuses in the front fuse box located near the steering wheel. Below are some of the things I learned as I tried to (crudely) monitor the power draw on the AGM battery:

1. Unlocking the car causes a the internal systems to draw over 20A of current. (sorry I don't have an accurate figure as I had my voltmeter set 20A and unlock made it go in overload)
2. Locking the car seems to be a 2-4 minute process as the internal systems complete various checks and balances.
   1. The draw starts at approx. 13-15A on clicking the button
   2. Then it drops to 5-6A within the first minute
   3. Then to 2-3A around the 2 minute mark
   4. Based on the state of the car before it was locked (i.e. was it driven or not, how long was it driven, how long has it been running, were only the systems turned-on, etc.), it goes down to 100-200 milliamp levels at or around 3mins
   5. Then finally, close to NO or intermittent 10mA draw at or around 6-10 minute mark
   6. Outside of that window, I am sure the car has built in RTOS that makes it wake up every now and then to perform other checks and balances
3. I'm sure I could've left fuses #23 & 24 (for LH and RH DVD) intact but I didn't want to leave any room for error. Maybe I will install them back in the future if and when I need it.

I hope this information will help someone! I want to thank everyone for providing their feedback as it did help me brainstorm a few ideas on how to go about my troubleshooting.


AGM Battery Monitoring

 

Interesting! I was going to make a current datalogger, but you've beaten me to it with your ingenious arrangement! Certainly bettter than locking yourself in the boot.

I wonder if the car wakes up from time to time? Anecdotal evidence says the housekeeping battery runs low after a few weeks, but at 10mA it should run for nearly a year. So there must be things the car does every so often.

Is there a tracker in your car?

What did you do with the RSE?

 

Very enlightening!

I can't phantom any reason to design a system this complicated, but someone surely has.

 

If I dont keep the systems battery connected to a smart charger my system battery, big one on the left as you look forward , will be almost flat after 2 weeks.
The starter battery , smaller one on right up to now has never gone flat.
Primary reason for it not going flat is that it is not used for anything but starting the car and one final task is for it to supply power to an electronic battery charger to charge the main battery.
Unlike many other cars the alternator only charges the starter battery. It dosnt charge the main battery. So after 2 weeks of the cars computer systems popping in and out of sleep, the battery dies. There is an actual computer module for the charging system.
Thankfully, vw audi's decision to fit a starter battery and use it not only to start but in emergency mode run the systems on the car at least means you can start the car and drive it.
My 911 996 had no such starter battery and that to would be flat if left for a pair if weeks. That was a right pain in the **** if you didn't use a smart charger.