Rechargeable battery (Audi A3 8L)

The installed 12V battery consists of six cans containing positive and negative plates that are dipped in a sulfuric acid solution. The battery's job is to generate current to start the car, ignition, and lighting, as well as for other consumers of electrical energy.

The battery is 100% efficient at 27°C. At -18°C the efficiency drops to 40%. Now, to start the engine, you need more than twice as much energy as you needed at 27°C.

Starting power (starting current) shows the battery's ability to start a car in very cold weather conditions. It shows the current in amperes that the battery delivers for 30 seconds at -18°C without the voltage dropping below 7.2 volts (the minimum level required for a reliable start). The higher this figure, the greater the starting power of the battery.

The reserve capacity indicates the time in minutes during which the battery delivers a current of 25 Amps at 27°C, i.e. the time during which the battery provides operation of all auxiliary devices in the car at night and in bad weather conditions with a faulty alternator.

In winter conditions at -18°C and below, the battery will charge poorly due to the increase in internal resistance. During short trips in winter, the energy expended by the battery for starting is not restored. As a result, the battery wears out, constantly discharges and eventually fails.

During the summer months, after long journeys, the engine becomes very hot and often difficult to restart. These "hot starts" sometimes require as much power as in cold weather, or more. This is especially true for high-compression, large-displacement engines and cars with air conditioning. This again highlights the importance of choosing the right battery for the car's engine.