A battery is one of the most important automotive components – it is responsible for engine start-up as well as the reliable operation of all electrical systems
The first reusable lead-acid power-storage battery was introduced in 1859 by French Physicist Gaston Planté. His design used an anode (negative electrode) made of lead and a cathode (positive electrode) made of lead dioxide. Both were submerged in a shared electrolyte solution.
While batteries had been around since the 1700s, the biggest difference was the design that allowed the battery to be recharged by reversing the natural chemical reaction.
According to the Department of Energy in the United States, 30 percent of automobiles manufactured in the early 1900s were electric powered. In later years, further advances in the technology resulted in lead-acid batteries becoming widespread in a variety of industries.
Today, the benefits associated with lead-acid technology mean that it is still being used to start vehicles.
Batteries used in a commercial application are regularly exposed to severe operating environments. In addition, truck batteries are normally mounted on the subframe and subjected to vibrations, so they are designed to
be mechanically stronger and harder than those used in cars.
The electrics in trucks (unlike those found in cars) are normally rated at 24V, and therefore require two batteries connected in series. This is necessary because the engine components in trucks (like the pistons and crankshaft of a diesel engine) are much larger than those found in cars and more torque is required to turn the motor over.
Buses and trucks also have electrical systems that place greater demand on batteries. Interior lighting, heaters and air-conditioning systems are often operated while the vehicle is switched off. Therefore, batteries need higher amperage for starting and have a greater capacity so that they do not run flat.
Battery performance is directly proportional to the working surface area of the lead plates, so batteries for trucks are also heavier and longer than those used in cars.
According to Willard Batteries South Africa, vented or flooded batteries are the most common form of lead-acid battery used in production vehicles. This type of battery has a cover with one or more openings through which the gas generated by the battery can escape.
Some may require top-up with distilled water, but batteries can also be fitted with tamper-proof plugs that prevent internal access to the battery. This type of battery has “free” electrolyte which means that the acid moves freely within it.
• The starting (cranking) or shallow-cycle type of battery is designed to deliver large bursts of power for a short time, as is needed to start an engine.
• The deep-cycle (or motive) type is designed to provide power continuously for long periods of time.
• Enhanced flooded batteries (EFB) were developed for use in stop-start vehicles. The EFB design incorporates a porous fibre material (sometimes called “scrim”) along with plates that are thicker than a conventional flooded battery.
Sealed maintenance-free (SMF) battery
Willard Batteries explains that some manufacturers use the term “maintenance free” to describe a battery that is sealed and has a water loss below a certain level. This term can refer to a number of different constructions, including ones with only a slight modification to the flooded style.
Valve regulated lead-acid (VRLA) battery
One major response to the changing power needs of today’s vehicles has been the development of absorbed-glass-mat (AGM) batteries. Gas will only escape from this battery if the internal pressure exceeds a predetermined level. Also, the electrolyte is immobilised, which means that the acid is suspended in either a gel or a glass-mat structure.
Willard says that VRLA batteries bring many benefits to vehicle system design. First, they typically have much lower internal resistance than traditional flooded batteries, meaning that they will heat up less during the charge/discharge cycle, which improves longevity.
Second, AGM batteries can be more deeply discharged than traditional flooded batteries. This is a critical benefit, since the increased electrical demands of modern vehicles mean that the battery must meet peak loads when alternator output is maxed out.
Third, due to their construction, AGM batteries are more vibration resistant than traditional flooded batteries and, because they are sealed and spill-free, can be stored and operated in any orientation.
Need to know
• Maintenance: the term “maintenance-free” isn’t entirely accurate, as all starter batteries require regular testing and cleaning, or lubrication of terminals, to perform at an optimal level.
• For a battery to remain in good working order, it should be maintained in a fully charged state by the vehicle’s charging system.
• Charging voltage coming from the alternator should be between 13,8 and 14,3V.
It would seem that the benefits associated with AGM batteries present an attractive proposition to fleet managers who want to avoid having to rescue forgetful drivers. Since they are more durable than traditional flooded batteries, have a lower internal resistance, and can be allowed to discharge further, they are likely to provide a cost benefit over the long term, too.