The original equipment battery in E83 vehicles is maintenance free, with the electrolyte typically lasting the entire service life of the battery under moderate climate conditions. However, caution must be exercised prior to disconnecting the battery, with the battery disconnection cautions needing to be read. The battery is located under the cargo floor. The original equipment BMW battery comes with a built-in hydrometer "magic eye", which determines the battery condition by eye color: green for adequate charge, black for inadequate charge requiring recharge, and yellow for a defective battery that needs replacement. Regular maintenance of the battery and its terminal connections ensures maximum starting performance, especially in winter when colder temperatures reduce battery power. It is important to ensure that the terminals, cable clamps and battery case are free of white deposits that indicate corrosion and acid salts, as even a thin layer of dust containing conductive acid salts can cause battery discharge. If the battery needs to be replaced, it should be replaced with one of equal or higher rating. The process involves working in the cargo compartment, opening the cargo load floor, disconnecting the negative cable first, then the positive cable, disconnecting the battery vent hose at the side of the battery, removing the hold down bolt at the front of the battery and lifting the battery out of the cargo compartment. Any corrosion in and around the battery tray and on cables ends should be cleaned away. When reinstalling the battery, the negative cable should be reconnected last.
