For a novice Class 8 truck driver getting accustomed to the industry, life on the open road can be intimidating. Drivers learn that part of their responsibility is knowing how to properly service and maintain their vehicle to ensure that cargo reaches its final destination. A catalyst of operational success lies in battery performance. Truck batteries provide the essential starting power needed to keep vehicles in motion and supply energy to all electrical components, including the radio, air conditioner, brakes, and windshield wipers.
With many different battery chemistries and OEM models to choose from, it can be difficult to pick the right battery for an application. A battery technical data sheet can be a helpful resource, but there is an abundance of terminology included in the overview that can prove to be confusing for someone new to the industry.
EACH IS DIFFERENT
Since a universal battery does not exist, there are different types of models that are suitable for different applications. Over the years, the chemical composition of a battery has evolved to meet and exceed vehicle demands, but the most widely used designs for heavy-duty applications are outlined as flooded lead acid, absorbed glass mat (AGM), and AGM batteries with TPPL technology.
Flooded Lead Acid
Conventional flooded lead acid batteries have been used to power commercial vehicles for more than 100 years. They employ a liquid electrolyte that floods the space between the positive and negative plates. Most commonly, the positive plates are manufactured with a lead-antimony alloy, and the negative plates are made with a lead-calcium alloy. While this is the lowest cost battery on the market today, it will only reach its potential life span if it is maintained properly, including monthly level checks and distilled water refills. Conventional flooded lead acid batteries are also sensitive to extreme temperatures and should therefore have limited exposure to direct heat or frigid weather to avoid weakening their charge and risking permanent damage.
Absorbed Glass Mat (AGM)
The advent of AGM batteries in the mid-1970s offered users a virtually maintenance-free energy storage solution with maximum power and charging capabilities. Unlike conventional flooded lead acid batteries where the internal electrolyte fluid moves freely in the battery pack, an AGM battery contains a fiberglass separator that is placed between each plate to absorb the electrolyte. This makes the battery non-spillable with no additional water or electrolyte ever required. Given that the plates can be sealed more tightly in the cell than flooded lead acid batteries, an AGM battery also offers better extreme shock and vibration resistance and is less prone to sulfation.
AGM Batteries with Thin Plate Pure Lead (TPPL) Technology
AGM batteries featuring TPPL technology use pure lead for the plates held with an engineered compressive force allowing for the elimination of calcium and antimony for strength and reducing the corrosive elements inside the battery. High-grade sulfuric acid is also used for the electrolyte. These high-purity materials allow TPPL batteries to build on the benefits of standard AGM designs.
As the TPPL designation implies, these batteries feature plates that are thinner than conventional flooded lead acid battery designs so more of them can fit inside the battery case. More plates provide greater plate surface area and reduce resistance, enabling greater cranking power. Compared with cylindrical six-pack AGM batteries, TPPL batteries offer 15% more surface area and thus 15% more energy storage with even more power capability for a given volume.
In North America, battery manufacturers have adopted the Battery Council International (BCI) Group Size number system. These specifications are used to identify the most basic elements of fitment, namely a battery’s physical size, terminal placement, and polarity. The OEM-recommended group number is a good indication to determine what batteries could be used to directly replace the standard battery supplied with the vehicle. Most manufacturers provide lookup tables to help identify the best battery to meet the basic needs of a specific vehicle.
Selecting the right battery for the application will have a major impact on its reliability. Having enough energy, power, operating temperature range, and cycle life to meet the economic needs of the application is critical in sizing and choosing the right battery(ies) for the application. When determining the needs of your application, specifications of added equipment as well as original equipment must be taken into consideration. Body builders, equipment upfitters, and experienced battery suppliers can assist in making sure you have the information required and can often do the appropriate calculations to determine the required characteristics of the battery bank needed for the application. This may mean a larger battery box allowing for more or larger batteries than originally provided with the vehicle.
There are several terms used to describe and measure a battery’s cells, modules, packs, and overall performance that are usually summarized on battery technical specification sheets. Below is a list of the most common technical descriptions to help identify the best battery for any application:
- State of Charge (SOC)—defined as the level of charge of a battery relative to a fully charged state, represented as a percentage.
- Depth of Discharge (DOD)—defined as the percentage of a battery that has been discharged relative to the overall capacity of the battery. For example, a discharge to at least 80% DOD is referred to as a deep discharge, and many battery manufacturers will include a spec sheet with recommended DOD for optimal performance and productivity.
- Cycle Life—defined as the number of discharge-charge cycles the battery can experience before it fails to meet specific performance criteria. The full operating life of the battery is affected by the rate, number, and depth of cycles: the higher the DOD, the lower the cycle life.
- Nominal Capacity (Ah) rating—defined as the amount of energy that can be provided by the battery at a particular constant current.
- Nominal Cell Voltage (V)—defined as the average voltage a battery cell outputs when charged; the V of a battery will depend upon the chemical composition and reaction behind it.
- Reserve Capacity (RC)—defined as the measurement of the number of minutes of reserve power the battery has at a 25-amp load. This is an extremely important battery characteristic, and the number is used on both starting and deep cycle batteries.
- Cold Cranking Amps (CCA)—defined as the number of amps a battery can deliver at 0 degrees F for 30 seconds and not drop below 7.2 volts. This rating is especially important when it comes to starting battery applications in cold weather environments. As a rule, in low-temperature scenarios, the more CCAs a battery has, the better.
Ultimately, heavy-duty truck drivers should weigh the pros and cons of different battery designs against their specific application demands, always be sure to follow the manufacturer’s guidelines for battery care and handling, and direct any questions to a battery professional. They should also refer to the vehicle owner’s manual for recommended battery specifications and cross-reference it with any spec sheets that come with products under consideration for purchase. This information should guide any driver’s selection of the ideal power solution for the next battery replacement.
ABOUT THE AUTHORS
Vicki Hall is the director of transportation technical solutions at EnerSys. Bryce Gregory is the systems product manager of transportation and specialty at EnerSys. Find out more, visit www.enersys.com.