The car battery provides the jolt of electricity needed to start your engine and power the accessories in your vehicle. It also stores energy.
The most common battery is the standard lead-acid variety, sometimes called a flooded battery. It requires occasional maintenance such as cleaning the terminals and topping off the fluid with distilled water.
Starter
A battery supplies electric current for powering lights, accessories and the engine. Most automotive batteries use a lead-acid chemical reaction to provide short bursts of energy. They are often referred to as SLI batteries (starting, lighting and ignition).
The electrical current triggers a series of reactions that generate the proper voltage needed to kick start an engine. The battery’s chemical solution contains plates of lead alternating with other materials immersed in an electrolyte solution of one-third sulfuric acid and two-thirds water. When turned on, the starter switch or ignition triggers the chemical process that produces the necessary voltage for starting a car’s engine.
The CCA or cold cranking amps rating tells you how much power the battery has to start your car under normal conditions in freezing temperatures. Some batteries have a Reserve Capacity or Amp-Hour rating, but the most popular ratings are CCA and CA. AGM batteries have thicker electrolyte so they can handle higher electrical demands and are more resistant to vibration, shock and temperature extremes. Solid-state batteries are newer technology that do not require a liquid base electrolyte.
Lighting
When your battery light illuminates, it’s a warning that something is wrong within the charging system. Ignoring it can lead to costly electrical damage in other areas of the vehicle.
A typical car battery consists of six cells, each with a positive and negative electrode (anode and cathode) separated by a woven separator and filled with electrolyte – sulfuric acid or lithium salt. A heavy strap connects the positive and negative plates of each cell together, and a pair of heavy terminals, plated with lead to resist corrosion, are mounted at the top.
Batteries are often marked with a code on their case that indicates the date of production – a format like YYWW or 1336. Starting batteries have thin plates to provide high instant current capability, while deep cycling or marine batteries have thicker plates for longer cycling performance. Car batteries that are marked as AGM or flooded have their electrolyte absorbed in a glass mat, which reduces the instant current capacity but improves the cycle life.
Electronics
Car batteries are the power storage devices that store chemical energy and turn it into electricity upon demand. They provide the energy to start the engine and run the lights and electrical systems in conventional vehicles.
When a battery is charged, electrons travel from the positive plates to the negative ones through a sulphuric acid electrolyte. The electrons that reach the negative plates are sucked up by the negative terminal on the vehicle. This creates a potential difference of 12 volts that can be used to power the electronics in your car.
The most common car batteries are lead-acid units. They have a plastic case that holds the acid and two heavy terminals that match up with positively and negatively charged lead plates in the electrolyte. Some are vented, with removable caps to add water as needed. Others are absorbed glass mat (AGM) units, which have no vents and cannot leak acid. They have pressure-activated relief valves to prevent overheating during recharging.
Charging
Car batteries need a battery charging system to recharge them when the engine is not running. Without it, the battery would die and the vehicle would not start.
A battery charger is like a small household battery and consists of a positive and negative electrode, an electrolyte, and separator. The negative and positive terminals are connected by a cable with a charger clamp.
Battery charging works by supplying electrical current to the battery and activating a chemical reaction inside its cells. This chemical reaction converts the battery’s sulfates into water and electrical energy, which it stores in its cells.
Before connecting your charger, make sure the hood is open. Carefully connect the charger’s red cable to the positive battery terminal and wiggle the clamp to ensure a good connection. Plug your charger into a power source and select the appropriate setting. Slower charge rates are better for your battery and reduce the risk of overcharging, which shortens its life.