Battery in battery compartment Audi A4
There is a separator between the plates. This separator separates the plates from each other, while the electrolyte passes through the microscopic pores that are present in the separator. The electrolyte is an electrically conductive liquid that is approximately 37 percent concentrated sulfuric acid and 63 percent distilled water.
Energy storage: internal parts of a 12-volt battery
Inside the battery, chemical processes take place, due to which energy is stored in the battery. When current flows, this chemical energy is converted into electrical energy. The most important task of the battery is to provide the starter with enough energy to start the engine. It's not that easy. Depending on the engine and type of starter, up to 2000 watts of power is needed at the moment of starting, when static friction must be overcome. To crank the engine, the starter needs only a fifth of this power. Starter current draw increases at low temperatures as lubricants thicken.
In the Audi A4, the battery is located in the battery section between the engine compartment and the windshield (in the back right side, under the cover). To gain access to the battery, remove the rubber seal forward and downward (arrows) and remove cover 1 (pic. left). The figure on the right shows an open battery: 1 - flexible jumper on the negative pole for connecting to the case, 2 - positive wire, 3 - battery fixing bracket, 4 - socket head screw. At the edge of the battery, above the positive terminal 2, a central gas outlet square is visible.
Concepts and norms
Designation: The designation is located on the battery case, it characterizes the properties of the battery. Example: 12V340A 70Ah (nominal voltage 12 V, low temperature current 340 A, nominal capacity 70 Ah).
Rated voltage: In all Audi A4 models, the nominal battery voltage is 12 volts. The actual voltage depends on the state of charge of the battery, it may be higher or lower than the nominal voltage.
Rated capacity: This parameter characterizes the battery's ability to store energy, the capacity is measured in ampere-hours (Ah). The battery capacity indicates how much energy a fully charged battery can deliver at 27°C in 20 hours, and the voltage must not fall below 10.5 volts (voltage at the end of discharge). The parking light of an Audi A4, for example, consumes 20 watts (all four lamps). With an onboard voltage of 12 volts, the battery, in accordance with the formula l \u003d W / V, delivers a current of 1.67 A. Thus, a battery with a capacity of 40 Ah can theoretically power a car with the parking light on for 24 hours. In practice, the situation is somewhat different: after 15 hours, the battery is discharged and the light goes out.
Low temperature test current: Specified discharge current in amps (A), which can be obtained from a 12-volt battery at a temperature of - 18°C, and the voltage should not fall below 9 Volts for 30 seconds and below 6 Volts for 150 seconds.
Self-discharge: The chemical processes inside the battery lead to a discharge, even if no consumer is connected to the battery. A charged starter battery loses approximately 0.5 percent of its charge daily. High temperatures, damage and pollution accelerate the self-discharge of the battery.
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