flat battery

Hello all Many threads cover this but I'm having trouble nailing down the answers to be specific to my car. So--- Battery failed completely and new one installed Before turning key to start all warning lights test and extinguish except airbag which goes out for 1 second then lights again...

After lay up over winter brand new Varta battery keeps going flat. Returned three times to the seller (a good friend of mine) and he believes that a fault on the car (Z3 3.0) is the reason. BMW tell me that the ECU goes into sleep mode after 16 minutes but does anyone here know the static...

Just went to go out in the Z after not using for about 3 weeks and battery totally flat. This also happened a few weeks ago but thought that it was due to lack of use and testing/checkin/unlocking and locking doors but no. Casually speaking to a Z owner from Porlock in a Minehead carpark weeks...