To ensure the durability and performance of the battery, periodically perform the following work:
Keep the battery and connecting cables clean. The top of the battery should always be dry to avoid leakage currents in the battery cells, which can lead to discharge.
The battery should always be filled with electrolyte to the level of the mark at the bottom of the case. To restore the electrolyte level, add only distilled water.
In cold weather, do not leave the battery in a discharged state, as this may cause the electrolyte to freeze. The electrolyte in a discharged battery freezes at a higher temperature than in a charged one.
Checking the battery
Electrolyte level
The battery is filled with electrolyte from a mixture of sulfuric acid and distilled water. Due to the evaporation of water, it is necessary to periodically check the electrolyte level and, if necessary, add distilled water to the battery. When adding, unscrew the battery compartment plugs and pour distilled water to the mark.
Electrolyte density
To check the density of the electrolyte, you need a densimeter. Unscrew the plug and lower the tip of the densimeter into the compartment (see fig. 264). Using a rubber bulb, suck the electrolyte into the densimeter until the float rises, read the density readings on the float. A density of 1.28 corresponds to the density of a charged battery, a density of 1.12 means the battery is completely discharged. Intermediate density values characterize the degree of contamination of the battery.
Article text obtained from the website: Mercedesman.ru
Fig. 264. Checking the density of electrolyte in the battery.
1 - densimeter,
2 - electrolyte level mark.
Battery charge
In a very discharged battery, add distilled water after charging. When charging, the density of the electrolyte increases and the battery may "boil". The initial charging current of the electrolyte should not exceed 10% of the capacity (5.5 A or 6.5 A). During the charging process, the current is automatically reduced. The battery is fully charged if the electrolyte density does not change within two hours of charging.
When charging, the plugs must be unscrewed to facilitate the passage of oxygen and hydrogen released during the charging process and the detonating gas formed from their mixture. During intensive charging, electrolyte may splash, so safety precautions must be observed. Never bring an open flame to the holes in the battery.
When using a regular charger for charging, the wires from the battery can be left connected. When using a charger with an accelerated charging process, the wires must be disconnected from the battery to avoid damage to the diodes in the generator, electronic devices, radio, etc.
Removal and installation
The battery is secured to a bracket in the engine compartment on the left side. Before removing the battery, disconnect the wires, always disconnect the negative wire first. To unscrew the battery mounting nuts, you will need a socket wrench with an extension.
When installing the battery, clean the terminals and lubricate. Install and secure the positive wire.
Starting the engine with a discharged battery
The easiest way is to use large-section wires to connect to the battery of another car. Copper wires are expensive, aluminum wires are cheaper, but they heat up a lot, which can damage the insulation, and when removing the wires, you can burn your fingers. First, connect the positive terminals of the batteries with a wire, and then connect the negative terminals. On the second car, start the engine and increase the speed to ensure the generator works.
Other well-known methods of starting an engine with a dead battery include towing with a second vehicle or accelerating the car with the help of several people.