The electrical system in a BMW car is complicated and operated by sophisticated electronics. BMW has their vehicles set up electronically so that you will have to take your car to the BMW dealership if you need to replace the battery; the new battery must be "registered" with the car's computer or it will have a shortened lifespan, not power your car properly and not receive proper charging from your car's electrical system. Registering the battery is the phrase used to describe resetting the car's computer so it will accept the new battery and work properly with it.
Take the BMW to the dealership or a mechanic shop that specialises in BMWs. The equipment to register a battery with your BMW's computer system is complicated, so your local mechanic shop, auto parts store or petrol station is unlikely to be able to perform the task.
Allow the mechanic's shop or dealership to replace your battery with an OEM BMW battery. Do not use any other type of battery except those designed to work with BMWs or it can void your car's warranty, short out the electrical system, and may not register with the computer properly.
Have the dealership or mechanic scan your BMW's computer with the BMW brand scanning tools. The mechanic will need to scan for generated error codes, document the codes and digitally erase them using the code reader. In some cases the mechanic will need to reprogram your BMW's electrical system to accept the new battery, as well as recalibrate the settings for a variety of electrical components, including some sensors. If you fail to do this, the vehicle's electrical system will still be programmed to the old battery and may not provide the battery with enough charging power to operate the car.
If your BMW's system is not reset to accept the new battery, it will only provide the amount of charge required by the old battery and may cause the battery to die prematurely. Also, any error lights or warning codes that generated when the old battery failed will continue to appear on the dashboard.