Your BMW X3 is equipped with a 6-cell 12-volt lead acid battery. Each cell consists of lead plates in a lattice completely covered with sulfuric acid (the electrolyte). The chemical reaction between lead and sulfuric acid produces a nominal 2 volts per cell; the six-cells together provide the approximately 12 volts required to operate electrical and electronic components in the vehicle. After the battery is used to start the engine, the alternator (powered via the engine accessory belt) takes over electrical generation and also replenishes the charge that the battery used in starting the engine.
During operation and also during recharging, the chemical reactions in the battery produce heat which causes the electrolyte (sulfuric acid) to evaporate. The cells in many older batteries are equipped with plastic caps which allow the evaporated electrolyte to escape. If the level of electrolyte drops below the tops of the lead plates the plates can become damaged; also the heat in the battery begins to build excessively at that point. If your battery has removable cell caps, be sure to remove them periodically and inspect the electrolyte level. If the electrolyte is at the same level as the tops of the lead plates, add clean distilled water to the battery.
Most modern lead-acid batteries are sealed so that the evaporated electrolyte cannot escape. However, a charging battery also produces hydrogen. This is discharged from the top of the battery using a small vent tube. Make sure the vent tube is not blocked or damaged and keep in mind that open flames or sparks around a charging battery are a potential source of battery explosion.
Heat, chemical reactions and electrical charges can cause battery connections to become covered with corrosive and insulating deposits. Any time you remove the battery terminals from the battery, be prepared to clean the metal surfaces with a metal brush. A solution of baking soda and water will neutralize acid deposits and clean the top of the battery and the battery compartment.
Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.
Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.
Vehicle models change and evolve as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.
The battery in BMW X3 models is located in the right side of the luggage compartment, under the carpet trim (red arrow). When replacing your battery be sure to use a high quality unit. Replacing the battery can be done in a short amount of time. Read battery connection notes before disconnecting battery. Before disconnecting your battery, remove key from vehicle and store in a safe place and note radio presets. When battery is reconnected or loses its charge the following items may need attention (depending on vehicle equipment): You may have to reset your clock, enter radio presets, initialize power windows and initialize the sunroof.
You can connect a battery charger directly to the battery or under the hood at the positive (+) and negative (-) grounding point junction. The battery junctions are located at right front strut tower. Red Arrow points to battery positive (+). Blue Arrow points to battery negative (-). However, I suggest removing battery from vehicle when charging. This will avoid filling your trunk with gases the battery emits during charging. Follow the manufacturer's instructions on setting and using the battery charger.
Jump Starting vehicle:
A vehicle with a discharged battery can be jump started using a good battery or a good battery in another vehicle. When jump starting: Be sure to work in a well ventilated area, batteries can produce an explosive gas. Wear gloves and eye protection and if battery acid comes in contact with your skin, immediately flush with water and seek medical assistance. Move both vehicles close together but do not allow them to touch. Turn ignition OFF in both vehicles.
Unclip and remove positive (+) terminal cover (cover on my vehicle subject vehicle was missing). Connect one end of positive jumper cable to positive (+) battery terminal of vehicle with good battery. Connect other end of positive jumper cable to positive (+) junction terminal (red arrow) vehicle with discharged battery. You will have to flip open lid on positive (+) junction connection. Connect one end of negative (-) cable to negative (-) battery terminal of vehicle with good battery. Connect other end of negative (-) jumper cable to negative (-) junction terminal (blue arrow) of vehicle with discharged battery. Start engine on vehicle with good battery. Allow to idle, then raise engine to 2000 RPM. Next, start engine of vehicle with discharged battery. Once vehicle with discharged battery starts, shut OFF any electrical accessories, radio, HVAC blower, etc. Carefully disconnect jumper cable in the reverse order you connected them. Allow vehicle with dead battery to idle to recharge the battery.
Loosen the 10mm nut on the negative (-) battery cable (blue arrow). Remove the negative cable and place out of the way in a place where it cannot come in contact with the negative terminal while replacing the battery. Flip the positive terminal protective cover up or remove it. Then loosen the 10mm nut on the positive (+) battery cable (red arrow). Remove the positive cable and place out of the way in a place where it cannot come in contact with the battery terminal while replacing the battery. Disconnect battery vent hose and lay aside (green arrow). The vent was missing on my subject vehicle. I will show you where it goes in the following steps.
Slide the battery toward the rear bumper. Lift battery up and remove from vehicle. Be careful and make sure you have a good grip, the battery is quite heavy. Clean battery compartment thoroughly. Clean corrosion from battery cable ends if present.