[John320d]

Is there an easy way to check battery drain when the car is at rest? and what is a typical drainage figure? On our other car I can just disconnect the positive battery lead and insert an ammeter between battery and lead.

[N5GKP]

BMWs with IBS monitor the standby current of the vehicle when it's 'asleep', typical current is 20-80mA, anything over 80mA is classed as a standby current violation.

If you can get your hands on a amp clamp, roll the boot catch, leave the car for a while to sleep (at least 30mins) and put the amp clamp around the negative lead. This will give you a true readout of what your vehicles standby current is.

The cars are really good at monitoring which control unit is actually causing the drain, however if you have something aftermarket wired in to a permanent live not supplied by a control unit it you'll simply end up with faults for standby current violation, none specific to control units. Generally if it continues for too long the vehicle will do a terminal 30B reset itself to try and 'reboot' the control unit and allow it to shut down properly incase it isn't going to sleep.