BMW E90 battery replacement: registration and coding
Does the battery on an E90 need to be registered after replacement?
Usually yes: the new battery is acknowledged with a diagnostic tool so that charging works correctly. Registration sets the capacity to 80 %, stores the mileage and resets the battery statistics. If the car has no battery sensor (on the battery's negative cable), registration is not necessarily needed.
Why does an AGM battery need to be coded to the car?
An AGM battery is charged at a lower voltage, at most 14.6 V, whereas in cold weather a regular lead-acid battery can get up to 15.2 V. If the battery type is not coded, the charging does not suit the battery and does not fill it properly.
What is the largest battery an E90 can be coded for?
The largest size that can be coded is 90 Ah. The options are 46, 55, 70, 80 and 90 Ah, and for AGM batteries 70, 80 and 90 Ah. A larger battery, for example 95 Ah, is coded to the nearest option, that is 90 Ah.
Can the battery be charged directly from the terminals?
In a car with a battery sensor, the battery must not be charged directly from the battery terminals. Charging is done from the jump-start points in the engine bay. The resting voltage of a full battery is over 12.5 V.