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 current drain on the battery in sleep mode. I am reading 70 ma which seems a bit high. Hopefully will be reading codes today but I suspect that they may not provide the answer. Otherwise car runs fine. Appreciate any information.