Battery — charging (Mercedes-Benz A-Class W168)

Precautionary measures

Do not disconnect the battery while the engine is running.

Do not short-circuit the battery, i.e. do not connect the positive (+) and negative (-) poles together. When short-circuited, the battery heats up and may burst.

Do not expose the battery to open flame. The electrolyte is corrosive. Do not allow it to come into contact with your eyes, clothing or skin. If necessary, wash it off with plenty of water.

Do not remove the plugs on a battery with a central gas outlet when charging, but make sure that the battery ventilation hose is connected.

Allow the battery to thaw if frozen. A charged battery freezes at approximately -65°C, a half-discharged battery freezes at -30°C, and a fully discharged battery freezes at approximately -12°C. Make sure that the thawed battery does not have a cracked casing. A battery with a cracked casing must be disposed of.

Charge the battery in a well-ventilated area or outdoors. When charging the battery without removing it from the vehicle, leave the hood open.

31. Remove the battery to charge it with a regular charger or a fast charger. If the battery remains in the engine compartment, the terminals must be removed from the terminals to charge it.

Warning! If you charge the battery without removing the terminals from the poles, you may damage the electronic control units of the car.

The temperature of the electrolyte when charging the battery must be at least +10°C.

Charger

32. Remove the battery, see the relevant chapter.

33. Battery of the conventional type. Check the electrolyte level before charging. If necessary, add distilled water.

If the charger has adjustable charging current, the charging current should be about 10% of the battery capacity.

This means that for a 50 Ah battery, the charging current should be around 5 A. The battery charging time is approximately 10 hours.

34. Connect the positive pole of the charger to the positive pole and the negative pole to the negative pole of the battery. The charger must be turned off at this point.

35. Insert the charger plug into the power outlet. If necessary, turn on the charger.

36. Check the battery temperature by touch or with your palm if the battery is charged with direct current. The electrolyte temperature during charging should not exceed +55°C. If necessary, interrupt charging or reduce the charging current.

37. Turn off (if necessary) charger after the battery is fully charged and disconnect the charger from the mains.

38. Disconnect the charger wires from the battery.

39. Check the battery charge, see the relevant chapter.

40. Place the battery in the vehicle tray, see the relevant chapter.

Batteries without central gas outlet

41. Before charging, unscrew the plugs of the battery cells and place them on the holes. This will prevent splashing of electrolyte caused by gases formed during charging.



42. Charge the battery until intensive gas formation in all cells stops, and until the increase in electrolyte density and voltage stops.

These indicators are compared by measuring the electrolyte density and voltage three times, performed at intervals of 1 hour.

43. After charging is complete, let the battery stand for about 20 minutes and only after the specified time has passed, screw the plugs into the cell holes.

Charging a discharged and sulfated battery

Batteries that have not been used for a long time, for example, if they have been in a vehicle that has not been used, gradually discharge and, in addition, may become covered with sulfate salt deposits.

The battery is considered to be deeply discharged if the open circuit voltage is less than 11.6 V. For the procedure for checking the open circuit voltage of the battery, see "Battery - checking".

Electrolyte (a mixture of water and sulfuric acid) a deeply discharged battery consists mainly of water.

Attention! At negative air temperatures such a battery may freeze and its casing may burst.

A heavily discharged battery becomes covered with sulfate deposits. This means that the plate surfaces harden and the electrolyte takes on a whitish tint.

If a discharged battery is charged immediately after discharge, the deposition of salts and hardening of the plates will continue, and the battery's ability to accept charging current will be limited.

A heavily discharged and sulfated battery should be charged with a small current. The charging current in this case should not be higher than 5% of the battery capacity.



The charging current, for example, for a battery with a capacity of 60 A/h should be 3 A. The charging current voltage should not exceed 14.4 V.

Warning: A deeply discharged battery cannot be charged using a fast charger.

Fast Battery Charging. Using an Auxiliary Battery

Boost charging or emergency engine starting using a booster battery should be the exception, as it exposes the battery to very high currents in a short period of time.

During accelerated charging, the charging current is 20% or more of the battery capacity.

Batteries that have been stored for a long time and are deeply discharged should not be charged using a fast charger, because in this case they are charged with what is called a surface charge.

Caring for battery terminals

44. Check the battery terminals for signs of corrosion. Corrosion of the terminals appears as white or yellowish powdery deposits.

45. Remove the battery.

46. Treat the battery terminals with a solution of water and soda. The resulting reaction will cause bubbles to form. The terminals will turn brown.

47. Clean the terminals (if necessary) with a wire brush or battery terminal cleaner.

48. After the reaction is complete, wash the terminals and the battery itself with clean water and let it dry.

49. Install the battery back into place.

50. With the ignition off, connect the wire terminals to the battery terminals.

51. Apply a thin layer of Vaseline or suitable lubricant to the terminals to prevent further corrosion.

Caution: Do not lubricate the poles immediately before installing the power wire terminals on them.

Storage of the battery

If the car will not be used for more than 2 months, the battery should be removed and stored in a charged state. The most favorable storage temperature is from 0°C to +27°C.

At these temperatures, the battery discharges the least. It is necessary to charge the battery no later than after 2 months of storage. Otherwise, the battery will become unusable.

If a battery that has been stored for a long time is charged using a fast charger, it either does not accept the charging current or appears to be charged with a so-called surface charge. Such a battery has all the signs of a faulty one.

Before considering a battery as faulty, it must be tested.

52. Measure the density of the electrolyte. If the density of the electrolyte in all cells differs by no more than 0.04 g/ml, then the battery can be charged with a conventional battery charger.

53. Check the battery after charging under load, see the relevant chapter. In workshops, special devices are used for this. If the battery voltage is below 9.6 V, the battery is faulty.

54. Check the density of the electrolyte. If the density is significantly lower in one or two adjacent cells (for example, in 5 cells the density is 1.16 g/ml, and in one - 1.08 g/ml), then the battery has a short circuit and is considered faulty.

55. Charge a deeply discharged and sulfated battery.

Self-discharge of the battery

Depending on the vehicle's configuration, the natural self-discharge of the battery is supplemented by the current consumption of various control devices that continue to operate even when the engine is off.



Therefore, the battery of a car that is not used for a long time must be recharged at least every 6 weeks.

If you suspect that there are leakage currents, check the on-board electrical system as follows, using a charged battery:

56. Set the ammeter to the upper measurement range.

57. Disconnect the ground (-) cable terminal from the negative battery terminal.

Warning! When you disconnect the battery from the radio, the security code is deleted, as well as all automatic settings on the radio station. Therefore, first read the provisions of Chapter "Battery - removal and installation".

58. Connect the positive (+) lead of the ammeter to the negative (-) terminal of the ground wire removed from the negative battery terminal, and the negative (-) lead of the ammeter to the negative battery terminal (see illustration).

Attention! The test can also be performed using a test lamp. But if the lamp connected to the ground wire terminal (-) and the negative pole of the battery does not light, then the test must be repeated using an ammeter.

59. Turn off all current consumers, turn off the clock (and other permanent consumers of electricity), close the doors.



60. Switch the ammeter to smaller and smaller measurement ranges until the ammeter starts registering voltage and the reading can be read (1-3 mA is acceptable).

61. Disconnect various electrical circuits by removing one fuse after another. If the ammeter readings drop to zero when disconnecting a circuit, the fault should be sought in that circuit. The sources may be corroded or dirty contacts, frayed wires, or an internal short circuit in the circuit.

If no fault is found in the circuits provided with fuses, it is necessary to disconnect the wires from devices not protected by fuses, such as the generator and starter.

If, when disconnecting from the terminals of any of the units not protected by fuses, the instrument readings drop to zero, then disassemble or replace the corresponding device.

If there is a loss of current in the starter or in the ignition system, it is necessary to check the ignition switch according to the diagram (workshop work).

62. Connect the negative (-) cable terminal to the battery.

63. Set up the electronic clock.

64. Enter the security code into the radio receiver.