Manufacturers are pouring billions of dollars on battery technology to increase the range and efficiency of new electric vehicles. If you open the hood of a new EV, though, you might find a standard 12-volt automobile battery. That could be perplexing but worry not: we will figure out why it’s there, as well as the mysteries of an electric car’s 12-volt mechanisms while we are at it.
Most electric automobiles are propelled by a single large, high-voltage battery pack containing rechargeable lithium cells. However, just like your fossil-fueled car, EVs have a standard 12-volt lead-acid battery. Although it may appear unusual or redundant, the old-school battery provides several critical functions. One of the drawbacks of a large, high-voltage battery is that it could be quite hazardous. It’s critical to keep the battery separate from the other car’s components. A contactor is used in electric cars to do this.
When the vehicle is in an accident, being repaired, or not being driven, the contactor permits the vehicle’s main battery power to be turned off. It’s a crucial safety feature that allows the primary traction electronics to get de-energized while not in use, preventing electrical fires and/or electric shocks. The term “contactor” refers to a large switch that regulates the current flow from the battery pack. Voltage is applied to a coil to turn on a contactor. This coil functions as an electromagnet, pushing a bigger set of contacts, allowing current to flow from the high-voltage battery. When you turn off the coil, the contacts separate, breaking the circuit and detaching the battery. It’s essentially the same as a large relay race.
The necessity for such a device raises a question: how do you activate this contactor to connect the primary traction battery to the other of the car’s electronics? Using a nice, dependable 12-volt battery is a simple method to do this. Fancier options, such as contemporary Li-Ion 12V batteries, would also work and are now available in some vehicles. Why reinvent the wheel when lead-acid automobile batteries have already been verified and certified to last in an automobile setting and are widely available? Or, for that matter, the battery.
The 12-volt battery is also useful in all of the ancillary systems found in modern automobiles. Historically, 12 volts have been used for electric windows, blower fans, headlights, and infotainment systems. They are all great, just the way they are. Because designing an electric drivetrain is difficult enough makes financial and operational sense to reuse existing, demonstrated designs for processes that can be largely reused.