An automotive battery or car battery is a rechargeable battery that is used to start a motor vehicle. Its main purpose is to provide an electric current to the electric-powered starting motor, which in turn starts the chemically-powered internal combustion engine that actually propels the vehicle. Once the engine is running, power for the car's electrical systems is still supplied by the battery, with the alternator charging the battery as demands increase or decrease. Battery in modern cars Gasoline and diesel engine Typically, starting uses less than three percent of the battery capacity. For this reason, automotive batteries are designed to deliver maximum current for a short period of time. They are sometimes referred to as "SLI batteries" for this reason, for starting, lighting and ignition. SLI batteries are not designed for deep discharging, and a full discharge can reduce the battery's lifespan. As well as starting the engine, an SLI battery supplies the extra power necessary when the vehicle's electrical requirements exceed the supply from the charging system. It is also 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 SLI batteries are lead-acid type, using six series-connected cells to provide a nominal 12-volt system (in most passenger vehicles and light trucks), or twelve cells for a 24-volt system in heavy trucks or earth-moving equipment, for example. Gas explosions can occur at the negative electrode where hydrogen gas can build up due to blocked battery vents or a poorly ventilated setting, combined with an ignition source. Explosions during engine start-up are typically associated with corroded or dirty battery posts. A 1993 study by the US National Highway Traffic Safety Administration said that 31% of vehicle battery explosion injuries occurred while charging the battery. The next-most common scenarios were while working on cable connections, while jump-starting, typically by failing to connect to the dead battery before the charging source and failing to connect to the vehicle chassis rather than directly to the grounded battery post, and while checking fluid levels. Close to two-thirds of those injured suffered chemical burns, and nearly three-fourths suffered eye injuries, among other possible injuries. Electric and hybrid cars Electric vehicles (EVs) are powered by a high-voltage electric vehicle battery, but they usually have an automotive battery as