|
If you do not hit the START button twice, it still will go to sleep, but instead of doing it immediately, it takes about 10-minutes, or until you lock the door. If you have comfort access and the fob is nearby, the car can periodically wake up, preparing for you to be close enough and unlock or open the door.
Not all chargers are created equal...some of them can be left on indefinitely, and, while there is some controversy over this, IMHO, if you don't have a charger that has an AGM mode, I do not believe it will fully charge the battery. THen, while the cables back to the battery are pretty large gauge, without that higher voltage, it will also affect the max charge. Some places say there's no need for a different charger, but some say it takes 0.3-0.4VDC more to fully charge an AGM than a normal lead-acid battery. I know that the Bosch C7 charger I have, when you put it in AGM mode, switches the recharging max voltage from 14.4, to 14.7. Maybe those Germans know something...
Very few things in modern BMWs are actually controlled with mechanical on/off switches. While they may look and act like a switch, instead of starting or stopping current via an internal switch, it is sending a signal to the computer, and something else, closer to it actually does the switching and this requires the computer to be awake, and the device(s) able to listen for their command to turn on or off. They all have low-power, sleep modes, but all it may take is one of them not shutting off and continuing to try to talk on the bus, which may wake up other things along the way. An example of this is the headlight switch panel...I changed mine to get the rear foglight functionality (the light was already in my car, just nothing to turn it on). The plug in the back of that switch panel has about 28g wires going in...obviously, not big enough to actually turn any lamp load on or off, plus there weren't enough of them for all of the individual functions it can control. There's a small chip in there, and it talks to the computer, and that directs something to actually switch power and turn the thing on or off. Same is true throughout the vehicle.
All it takes is one of the boxes not shutting down, or your fob to be too close (maybe near max range is the worse, causing things to start, then waiting to go to sleep again, and repeating). Maybe we all need a shielded box to drop our fobs into while home. Because the fob is out of range when you say leave it parked at an airport for a vacation trip sort of supports these thoughts...it won't be getting tricked into waking up periodically until you actually return.
The dealer has the equipment to test the standby current draw, and the computer can help in trying to see what may be on when it should be off. The idea about trying a fuse or two at a time should help to isolate it, but with the networked CANbus in these vehicles, I'm not sure that's fully true.
|