That changed in the ’50s when vehicle electric systems transitioned to 12 volts, thanks to evolving car designs and features that required more power. To this day, most vehicles use 12-volt batteries. Another important milestone in the history of car batteries occurred the following decade with the introduction of the absorbed glass mat battery.
The vast majority of modern cars still use a 12-volt battery because, over the decades, an entire industry has been built around this voltage despite limitations that became apparent over time. However, a shift is happening, and some vehicles are moving to a 48-volt system, which has many advantages.
EVs use their DC-to-DC converter to step down the voltage to 12 volts to power all auxiliary systems without passing the current through the 12-volt battery. The most important function served by the 12-volt battery in these vehicles is to wake them up and keep some systems online while the vehicle is off.
A combination of size, cost and ease of manufacturing has kept 12-volt batteries alive in the industry for close to 100 years, but with 48-volt systems on the rise, the next revolution in car battery chemistry might be just around the corner.
What the 12-volt battery is used for and when it’s used varies from EV to EV. When an electric vehicle is turned off, its traction battery is disconnected from its electrical system using special contactors, which are electronically controlled switches.
In the early days meaning before WW1 there was no standardization. Some cars had 6 volt, some 12, some had 24 volt systems. Others had no battery at all. Ford did not even offer a starter until 1918 or so. Some very early cars, 1900 and earlier, used dry cell flashlight batteries for ignition.