Battery Charging

Items 6, 11-14 do not apply to the low-maintenance batteries fitted to BMW 5 Series vehicles. Observe the operating recommendations for low-maintenance batteries.

* Never short-circuit the battery, i.e. do not connect (+) and (-) together. A short circuit may cause the battery to overheat and crack. Do not expose the battery to open flame. Electrolyte is poisonous; keep it away from eyes, skin, and clothing. If electrolyte makes contact, flush the affected area thoroughly with water.

PROCEDURE

1. Before charging the battery, disconnect both the positive (+) and negative (-) cables from it. Disconnect the negative cable first.
2. Before charging the battery, check the electrolyte level and add electrolyte if necessary.
3. If the battery is frozen, allow it to thaw before charging. A fully charged battery freezes at -65°C; a half-charged battery freezes at -12°C.
4. If the battery has been discharged for a long time, it may not be possible to charge it fully, or it may not be possible to charge it at all. In this case, charge the battery with a low current over a longer period. After charging, check the electrolyte specific gravity.
5. Before charging the battery, check its voltage. Refer to the Battery Testing section.
6. Remove the filler caps from the battery and place them over the openings. This prevents electrolyte spray from reaching the paintwork while allowing gases produced during charging to escape.
7. Charge the battery only in a well-ventilated area. When charging a battery installed in the vehicle, open the luggage compartment lid.
8. For normal charging, the current should be approximately 10% of the battery capacity. (For a 50 Ah battery, the charging current is therefore 5 A.) The charging time is approximately 10 hours.
9. Connect the positive battery terminal (+) to the positive (+) terminal and the negative terminal (-) to the negative (-) terminal of the charger.
10. The electrolyte temperature during charging must not exceed +55°C. Otherwise, stop the process or reduce the charging current.
11. Continue charging until gas is released and the electrolyte specific gravity and voltage no longer rise over three consecutive measurements taken at one-hour intervals.
12. After charging, check the electrolyte level and add distilled water if necessary.
13. Check the electrolyte specific gravity. If the specific gravity in one cell differs significantly from the others (for example, five cells read 1.26 g/ml and the sixth cell reads 1.18 g/ml), the battery is faulty and must be replaced.
14. Allow gases to escape for 20 minutes, then close the filler caps.

* Never start the engine with the battery disconnected.