A battery stores energy for running your car’s electrical systems. Its two most important functions are starting and supplying power for driving.
A standard auto battery uses lead-acid technology, with plates of lead sulfate and other materials immersed in an electrolyte solution of water and sulfuric acid. We call these batteries flooded or conventional (or SLI, for starter, lights and ignition). Some have vents to allow air to flow in and out to regulate the developing current.
Types
There are many types of car batteries and the type you need depends on the power demands of your vehicle. One of the most important factors is Cold Cranking Amps (CCA) which measures a battery’s ability to start an engine in freezing temperatures.
The oldest and most common are lead-acid batteries. These have an outer case that holds a series of lead plates bathed in acid that creates the electricity to run the car’s accessories and start the engine. They are known as SLI batteries (starting, lighting and ignition).
More recent car batteries use an absorbed glass mat or AGM design that is spill-proof and doesn’t need periodic replenishment of the acid. Newer lithium-ion batteries have high power-to-weight ratios and high energy efficiency while providing better high temperature performance than lead-acid batteries. They also offer lower internal resistance allowing them to charge faster. Research continues into solid-state battery technology that would eliminate the need for a liquid base and could be used in future electric cars.
Performance
Batteries provide an essential power boost to the vehicle’s electrical system. They also help stabilize voltage spikes from turning on and off accessories that pull a lot of energy.
Traditional battery ratings include Cold Cranking Amps (CCA) and Reserve Capacity (RC). CCA indicates the amount of power a standard auto battery can supply for 30 seconds at 32 degrees F. Reserve capacity measures a battery’s ability to hold a charge in the face of heavy loads.
Li-ion batteries self-discharge at a slower rate than other types. Temperature and charging patterns affect long term battery life, but manufacturer recommendations and good usage habits can reduce degradation rates. EV battery protection buffers control the usable state of charge window, limiting extreme low and high charging for battery health and maximum driving range. The Chevrolet Volt, for example, features large buffers and liquid thermal management to slow degradation. The buffers are dynamic, decreasing as the battery ages. This allows the battery to continue providing a minimum of 100 miles per charge, even as its state of charge decreases.
Maintenance
Whether you drive a daily commuter or weekend sports car, a reliable battery is essential to getting you where you need to go. Keeping your battery charged and free from damage helps to ensure that the electronics in your vehicle work properly, including crucial safety systems like anti-lock braking.
When a battery is not in use, it will lose a small amount of charge every month. To minimize this loss and to prevent lead sulfate from building up on the battery plates, periodically check the battery’s charge level and recharge it as needed.
Make sure the terminals are clean; rust and corrosion inhibit the flow of electricity. Use a wire brush or battery terminal cleaning tool to remove any deposits, then scrub with a solution of water and baking soda. After cleaning, reattach the terminals and spray with a corrosion-resistant product (available at parts stores). If your battery has a hold-down bar, tighten it to help stabilize the battery and prevent excessive vibration.
Warranty
Most battery manufacturers offer a warranty on their products. The duration and details vary from plan to plan, but most warranties cover manufacturing issues as well as defects in materials or workmanship.
The warranty will usually include a free replacement for the product during its lifetime, but there will also be limitations on how many cycles or years the battery can last before needing a replacement. The number of cycle is typically printed on the receipt, as are the warranty terms and conditions.
If a battery is transferred to another owner, a new receipt will need to be issued, as the warranty will generally expire on the date written on the previous receipt. Additionally, using a battery for purposes other than those for which it is designed, advertised or marketed will void the manufacturer’s warranty. The exact process of filing a warranty claim will differ from provider to provider, but there are certain common exclusions.