How Does a Vehicle's Battery Work?
Other People Are Reading
-
What All Batteries Have in Common
-
All batteries do the same thing: convert chemical energy into electricity through the reaction of two different substances. The arrangement of a battery is to have two electrodes--an anode (negative terminal) and a cathode (positive terminal), each made from a different substance. These are not placed in direct contact due to the risk of a short circuit, and are instead connected by a medium or electrolyte. Using the electrolyte, the anode and cathode react so that positively charged electrons travel to the cathode and negatively charged electrons travel to the anode, forming electric current. When a device is connected to the battery, it forms a circuit through the battery's negative and positive terminals. The current flows out of the battery, through the device and back to the battery--but without some of the charged particles that make up the electric current.
Lead-Acid Batteries
-
The batteries used in most cars, motorbikes and boats are lead-acid designs. The anode and cathode are made of lead and lead dioxide. The electrolyte is a solution that is one-third sulfuric acid. These parts react as previously described to produce an electric current. In lead-acid batteries, as power is discharged from the battery, the anode and cathode undergo a chemical reaction that converts them into lead sulfate. Lead-acid batteries are a venerable design, and they have the worst stamina and power-to-weight ratio of any battery type in common use today. However, they can deliver a big charge in one jolt, making them ideal for engine starters. Hybrids and newer all-electric vehicles, on the other hand, have a need for greater sustained power output, and use a different type of battery.
-
Nickel Metal Hydride Batteries
-
Some hybrids and all-electric cars use the nickel-hydride battery design. These use nickel oxyhydroxide for a cathode, a hydrogen-absorbant material as the anode, and potassium hydroxide as the electrolyte.
Lithium Ion Batteries
-
Other hybrids and all-electrics use lithium ion batteries that are similar to the ones used in mobile phones and laptop computers. The cathode is a lithium oxide or phosphate, the anode is typically graphite, and the electrolyte is a solution of lithium salts and an organic solvent such as ether. In lithium ion batteries, the electrolyte tends to break down on the anode during recharging.
Recharging
-
When current is applied to a rechargeable battery, the electrochemical reaction is reversed. For example, when a lead-acid battery is recharged, the anode and cathode partially reverse their mutual transformation into lead sulfate. Conventional vehicles with lead-acid batteries charge them either by using an alternator (a mini-generator powered by a belt that transfers mechanical power from the engine to the battery) or through the use of a battery charger. Car battery chargers transform the voltage from a wall outlet to provide electric current suitable to the battery. Hybrid batteries are charged using a generator powered by the car's gasoline engine, or using energy captured from braking by a mechanism in the brakes in a process called regenerative braking. Some hybrids that have been refitted into plug-in hybrids can be charged using current from external outlets.
-
