Pic. 9.1. Battery location under the rear seat on the right side in the T-model (wagon) similar to the layout in the sedan: 1 - rechargeable battery; 2 - negative terminal, «weight» (–); 3 - ventilation tube; 4 - battery mount; 5 - fuse block
On all E-class vehicles, the battery is located under the rear seat on the right side. You have to remove the rear seat cushion to access the battery (sedan) or fold down the right rear seat (T-model), the battery itself is closed with an additional cover. In the engine compartment there is a control contact for checking the battery. It is marked with the symbol «+» (pic. 9.1).
Pic. 9.2. Battery device: 1 – positive electrode grid; 2 - positive electrode; 3 - separator; 4 – negative electrode grid; 5 - negative electrode; 6 - block of negative electrodes; 7 - battery section; 8 - block of positive electrodes
Six batteries connected in series form a battery (12 V) (pic. 9.2). One battery consists of a block of positive and negative plates, which together create a voltage of 12 V. The plates consist of lead grids that are filled with an active electrolyte. The positive plates are made of lead dioxide, the negative plates are made of pure lead. A separator is installed between them. It separates the plates, preventing short circuits, but the electrolyte can pass through its tiny pores. An electrolyte is a conductive liquid that is approximately 37% concentrated sulfuric acid and 63% distilled water.
Accumulator battery
Marking. Located on the battery case, indicates its characteristics. For example, marking «12 V 74Ah 350 A» means the following: 12 V - nominal voltage; 74 Ah - rated capacity; 350 A - control discharge current.
The nominal voltage of the battery is 12 V. The actual voltage depends on the state of charge of the battery and may be higher or lower than the nominal voltage.
The rated capacity is the current that a fully charged battery can deliver for 20 hours at a temperature of +27°C without a voltage drop at the terminals of at least 10.5 V.
The reference cold discharge current reflects the current capacity of the battery in the cold state. The 12V discharge current that a battery can deliver at -18°C without the voltage dropping below 9V for 30s and 6V for 150s.
Self-discharge is a chemical process that occurs in a battery and leads to its discharge when consumers are not connected to it. A charged new car battery loses approximately 0.5% of its charge daily. High temperatures, damaged or dirty battery covers accelerate the self-discharge process.
Battery - energy storage
Inside the battery, chemical processes take place, due to which it generates and accumulates energy. During current transfer, the energy of a chemical reaction is converted into electrical energy. The most important function of the battery is to provide the starter with energy to start the engine. Depending on the model of the engine and starter, the power consumption at the time of starting can be 5000 watts. This is also due to losses in overcoming frictional forces to crank the crankshaft of a warm engine - the starter needs only a fifth of this power, consumption increases at low temperatures, because then the lubricants harden.