Checking battery condition, care and charging (BMW 5 Series E28)

Annually or every 20,000 km.

Tools and materials needed for battery maintenance.

1 — Face shield/safety glasses - when removing traces of corrosion with a brush, particles of crystallized acid can easily get into the eyes

2 - Baking soda - an aqueous solution of baking soda can be used to neutralize the acid

3 - Acid-free Vaseline - a layer of Vaseline applied to the battery terminals will help prevent their corrosion

4 — Terminal/wire end stripping tool - this device with a wire brush will remove all traces of corrosion from the battery terminals and wire ends

5 - Impregnated felt washers - installing such washers on each battery terminal directly under the wire tips will help prevent corrosion

6 - Puller - sometimes the wire ends are very difficult to remove from the battery terminals, even after completely loosening the nuts/bolts. This tool will help you remove the ends vertically upwards without damage

7 — Terminal/wire end stripping tool - another type of stripping tool, a slightly modified version of point 4, performing the same functions

8 - Rubber gloves - another means of protection when working with a battery; remember that there is acid in the battery!

Check and care

When working with a battery, certain safety precautions must be taken. Battery cells always contain highly flammable hydrogen, so never allow a lit cigarette or other open flame to approach the battery. Battery electrolyte is a sulfuric acid solution, which causes serious injuries if it gets into your eyes or on exposed areas of the body. In addition, the acid corrodes clothing and paints. When disconnecting a battery, always disconnect the negative cable first and reconnect it last!

Battery maintenance is a very important procedure to avoid stopping your vehicle on the road due to a discharged battery. Several tools are required to perform the maintenance procedure.

Before beginning any maintenance procedure, always turn off the engine and all electrical equipment first, then disconnect the negative battery cable.

If your vehicle's radio is equipped with an anti-theft system, make sure you enter the correct code before disconnecting the battery.

If the instrument cluster displays the wrong language after connecting the battery, refer to Section Anti-theft audio system and instrument cluster language, which describes the procedure for installing the required language.

BMWs are usually equipped with low-maintenance batteries. You can remove the can lids and add distilled water. The latest models can be equipped with completely maintenance-free batteries, which are completely sealed.

1. Remove the caps and check the electrolyte level in each battery can. It should be above the plates. There is usually a level indicator on each can. If the electrolyte level is below the norm, add only distilled water and then close the can caps.

Overfilling the cells may cause electrolyte to spill during boost charging, causing corrosion and damage to components near the battery.

2. If your vehicle's positive battery terminal and cable clamp are equipped with a rubber cap, make sure it is not torn or damaged. It should completely cover the terminal.

3. It is necessary to periodically inspect the external condition of the battery for damage such as cracks in the casing.

4. Check that the battery cable clamps are tight enough to ensure a good electrical connection. Check each wire along its entire length for cracks and frayed insulation and wires.



5. If traces of corrosion are detected (usually presenting as a loose white coating)...



...disconnect the wires from the terminals, clean them with a special brush and reconnect them. Sometimes, in cases where corrosion has destroyed the nut, special pliers are required for this procedure (always disconnect the ground wire first and connect it last!).





6. Regardless of the type of stripping device, the result should always be a clean, shiny terminal surface.



7. When stripping the wire ends, it is necessary to remove all traces of corrosion (the inside of the tip is tapered to match the shape of the battery terminal, so don't remove too much material).

8. Corrosion can be minimized by installing specially treated washers, available from auto parts stores, or by coating the terminals and wire clamps with acid-free petroleum jelly or a suitable lubricant after connecting them.

9. Make sure that the battery tray is in satisfactory condition and that the clamp bolt is securely tightened. If the battery has been removed from the tray (see chapter On-board electrical equipment system, which describes the removal and installation procedure), make sure that no parts or other foreign objects are placed on it during installation. When tightening the fastening clamp, do not tighten its bolt too tightly.



10. Traces of corrosion from the tray, battery case and surrounding surfaces can be removed using a solution of baking soda and water. Apply the mixture with a small brush, let it sit and then rinse with plenty of clean water.

11. Metal surfaces of the vehicle that have been subject to corrosion should be coated with a zinc-based primer and then painted.

For more information on the battery and jump starting, see Chapter On-board electrical equipment system.

Charger

Manufacturers recommend removing the battery from the vehicle to charge it, as the gas released during this procedure can damage the vehicle's painted surfaces or interior, depending on the battery's location. Rapid charging with the battery cables connected can cause damage to the vehicle's electrical system.

1. Remove all caps from the battery jars (if they exist) and cover the holes with a clean rag to prevent electrolyte from spilling. Disconnect the negative battery cable and connect the charger cables to its terminals (positive to positive, negative to negative), then plug the charger into the mains. If it has a switch, make sure it is set to the "12 volt" position.

If your vehicle's radio is equipped with an anti-theft system, make sure you enter the correct code before disconnecting the battery.

If the instrument cluster displays the wrong language after connecting the battery, refer to Section Anti-theft audio system and instrument cluster language, which describes the procedure for installing the required language.

2. If you are using a charger with a current greater than two amps, check the battery regularly while charging to ensure that it has not overheated. Using a slow charger, you can safely leave the battery to charge overnight after checking regularly for the first two hours. Certain precautions may be required when charging maintenance-free batteries (for example, using a very low current charger). There may be a warning label on this battery, but if there isn't, consult your BMW dealer or an electrician at a car repair shop.

3. If the battery jars have removable caps, check the specific gravity of the electrolyte with a hydrometer every hour during the last few hours of the charge cycle. Inexpensive hydrometers are available at auto parts stores - follow the instructions on the package when using them. The battery is considered charged if the specific gravity of the electrolyte does not change over two hours and the electrolyte bubbles freely in the jars. The specific gravity of the electrolyte in the individual jars should be nearly the same. If this is not the case, one or more of the battery jars is bad and should be replaced.

4. Some maintenance-free batteries have a built-in hydrometer at the top, which has a window - a color indicator of the battery's charge level. Usually, a brightly colored window means the battery is fully charged, and a dark color indicates that additional charging is needed. More precise instructions are provided in the battery manufacturer's instructions.

5. If the battery is sealed and does not have a built-in hydrometer, you can check the charge level by connecting a digital voltmeter to the battery terminals. A fully charged battery will show 12.6 volts or more.

More complete information about the battery and jump starting can be found in Chapter On-board electrical equipment system.

[The original material is located on the website: «BMWMan»]