An automotive battery is a rechargeable battery that supplies electric energy to an automobile. Its main purpose is to start the vehicle but it also handles lighting, ignition and charging mobile devices. Once the engine is running, power for the car is supplied by the alternator. These batteries are designed to release a high burst of current, measured in amperes, and then be quickly recharged. They are not designed for deep discharge and a full discharge can reduce the battery’s lifespan.
As well as starting the engine, the battery supplies the extra power necessary when the vehicle’s electrical requirements exceeds the supply from the charging system. It is also acts as a stabilizer, evening out potentially-damaging voltage spikes. While the engine is running, most of the power is provided by the alternator, which includes a voltage regulator to keep the output between 13.5 and 14.5 V.
Modern batteries are typically lead-acid type and is actually six cells connected in series.
Battery electric vehicles are powered by a high-voltage electric vehicle battery, but they usually have an automotive battery as well, so that they can be equipped with standard automotive accessories which are designed to run on 12 V.
An automotive charging system is made up of three major components: the battery, the voltage regulator and an alternator. The alternator works with the battery to generate power for the electrical components of a vehicle, like the interior and exterior lights, instrument panel and USB ports.
Alternators are typically found near the front of the engine and are driven by the crankshaft, which converts the pistons’ up-and-down movement into circular movement. Some early model vehicles used a separate drive belt from the crankshaft pulley to the alternator pulley, but most cars today have a serpentine belt, or one belt that drives all components that rely on crankshaft power. Most alternators are mounted using brackets that bolt to a specific point on the engine. One of the brackets is usually a fixed point, while the other is adjustable to tighten the drive belt.
To make an engine start it must be turned at some speed, so that it sucks fuel and air into the cylinders, and compresses it. The powerful electric starter motor does the turning. Its shaft carries a small pinion (gear wheel) which engages with a large gear ring around the rim of the engine flywheel.
The starter needs a heavy electric current, which it draws through thick wires from the battery. A solenoid is used to manage the current – an arrangement where a small switch turns on an electromagnet to complete the circuit.
The starter motor must not turn more than it has to in order to start the engine partly because the starter uses a lot of electricity, which quickly runs down the battery.