Your gasoline-powered car has a battery. It relies on the battery to power everything from the headlights to the entertainment system. And of course, you need a battery to start the car. So how does the battery stayed charged? It’s not like you’re plugging your car into a charger every night.
When engineers added batteries to cars some one hundred years ago or so, they also devised an ingenious piece of kit that truly revolutionized driving. What was that piece of kit? An alternator. Thanks to the alternator in your car, you don’t have to remember to recharge the battery. It recharges as you drive.
Transferring Kinetic Energy
One of the fundamental laws of physics states that energy cannot be created nor destroyed. It can only be transferred. The alternator works on that principle. It transfers kinetic energy from engine to the battery. As long as the alternator is working properly, it keeps the battery charged.
An alternator is a semi-cylindrical device attached to the front of your motor with a bolt or two. You may or may not be able to see it looking through the hood of your car, depending on the configuration of the engine compartment. It is normally toward the front of the motor, very near the fan.
A steel rod protruding from the front of the motor accommodates a series of pulleys. One pulley provides the connection to the alternator via a belt. As the pulley turns, it forces a companion pulley on the alternator to turn. Inside the alternator is a small electric generator that sends electricity to the battery.
Energy transfer is what actually takes place here. The alternator transfers kinetic energy produced by your engine to the battery, after converting it to electricity. Your car’s electrical components draw energy from the battery as you drive. It is all pretty simple in practice.
Charging Consumer Batteries
Charging consumer batteries also requires a transfer of electricity. The process is somewhat different, but the scientific principle is the same. For example, consider your AA batteries from Pale Blue Earth. They are designed to be recharged using any standard USB port. Once again, recharging is a matter of energy transfer.
When you plug the batteries into a USB port, energy is transferred from the source of the power to your batteries. That source might be your computer, a bedside lamp, or a wall outlet. You might even have a portable charging battery for your cell phone. You could charge your lithium-ion batteries by plugging into it. Energy would be transferred from it to your batteries.
When Energy Transfer Fails
Getting back to your car and its battery, what happens if energy transfer fails? That’s a big problem. It is more of a problem today than it was 30 or 40 years ago because so many modern car components are electronic.
All those electronic components are constantly drawing battery power. Therefore, your alternator is continually working to keep the battery charged. As it starts to fail, it produces less electricity. At the point of imminent failure, you notice it. Your headlights do not shine as brightly as they used too. The heater fan doesn’t blow is hard. It is all because the electric components are drawing more energy than the alternator is producing.
When the alternator stops working altogether, so will your car. The only solution is to replace it and recharge the battery. Incidentally, you could run a car without an alternator and battery back in the 70s and 80s. You wouldn’t have had access electric components, but the non-electronic engine would still run. This is not the case today.