TPPL technology broadens options
29 May 2020
Warehouses and production areas are under increasing pressure to maximise productivity and return on investment.
This has led to more attention on the role of materials handling vehicles, particularly the cost and performance of the batteries and the technology that power them.
As an example, users of material handling vehicles today will not accept a loss in productivity due to battery-related downtime. It is simply no longer possible to remove a vehicle from service to charge or change out batteries and perform routine maintenance tasks. In addition, there is a trend to lease vehicles instead of making an outright purchase. Changing a battery during a lease term is undesirable because the new battery will not be spent by the end of the contract, leading to waste.
Choosing a battery solution is affected by factors like initial cost, performance, maintenance, charging, stock management and recycling. High performing technologies, such as Thin Plate Pure Lead Batteries (TPPL), offer an attractive alternative to both the traditional solutions of lead-acid or new-comers such as lithium-ion (Li-ion). There are two main types of TPPL battery. The first is a “standard” TPPL solution supplied as a direct alternative to lead-acid batteries. The second is a TPPL solution enhanced with carbon addition. This battery offers a high-performance and cost-effective alternative to Li-ion batteries, especially in heavy-duty applications, thanks to greatly extended cycle life.
Factors that compromise truck productivity
Each battery type has different charging and safety requirements, which impact on truck productivity.
Flooded lead-acid batteries typically need long charging cycles during or after a shift. This means taking a vehicle out of service or changing the battery. For safety reasons, lead-acid batteries require dedicated charging rooms with ventilation. Regular water top-ups are part of normal operation, but also create the risk of acid spills. Also, overcharging batteries by 10-20% minimises stratification but adds to the energy demand. All these factors contribute to the total cost of ownership (TCO) for a lead-acid battery setup.
Gel type valve-regulated lead-acid (VRLA) batteries have advantages over flooded lead-acid batteries. They do not require water top-up, and their overcharge factor is only 8-10%, thus reducing the energy demand for charging. However, they do not allow for opportunity charging or fast charging with high currents. Batteries must be taken out of service for charging, which takes from 8 to 10 hours.
Li-ion batteries are more expensive, but they offer a higher-performance solution suitable for heavy-duty applications. They have the advantage of flexible charging like ultra-fast and opportunity charging. Li-ion technology also has a high-power density and zero maintenance requirements. Their extended cycle life means that they can outlast the standard life of a forklift truck. Li-ion batteries do not require ventilation, but they do need electronic battery management systems for safety, control and optimisation. A disadvantage is that the lack of Li-ion recycling options makes disposal of these batteries expensive.
TPPL batteries have the benefit of flexibility without the higher-cost of Li-ion. The NexSys Core battery from EnerSys is an example. It is suited for low and medium-duty applications. The NexSys Pure battery uses TPPL technology with the addition of carbon. It is optimised for medium to heavy-duty applications as an alternative to Li-ion batteries.
TPPL battery technology
TPPL batteries have up to 10% more energy content than flooded lead-acid batteries and up to 20% more than Gel VRLA types. This is achieved by the higher number of plates and reduced plate thickness. However, it is the flexible and rapid charging ability that separates this battery class from other lead-acid alternatives. TPPL technology allows Partial State of Charge (PSoC) cycling without compromising on battery life. A cycle life of 1500 at 60% depth of discharge (DoD) is possible and even more at shallow DoD.
With opportunity charging, trucks can complete an entire shift or even longer without losing time for recharging. Fast charging is also possible with charge rate from 0.25C5 to 0.4C5. The combination of charging speed and increased battery capacity allows truck fleets to operate with fewer batteries, thus supporting a lowe TCO.
The NexSys Core battery using TPPL technology is also available in an ATEX (ATmosphères EXplosives) version that allows materials handling vehicles to work safely in hazardous areas where there is an explosion risk.
TPPL battery technology with carbon addition
The NexSys Pure battery builds on the TPPL base with added carbon in the active material. The chemical changes in the battery yield improved performance in terms of lower internal resistance and higher charge acceptance. The NexSys Pure battery delivers ultra-fast recharge and exceptional PsoC cycling performance.
TPPL batteries with carbon added have high specific power and can sustain up to 160% energy throughput per day. This means that batteries can last for 2 to 3 shifts using multiple opportunity charges. Addition of carbon in the active material formulation and the use of a dedicated charging profile improves a NexSys Pure battery’s life, up to 50% more than NexSys Core battery (depending on application and use). This battery can outlast the rental contract for most trucks.
As a bonus, disposing of TPPL batteries with carbon is profitable compared to the extra costs to dispose of Li-ion.
Battery charging technologies
Battery charging systems are as influential in battery performance as the batteries themselves. NexSys and NexSys+ battery chargers provide intelligent charging to their TPPL range of batteries. High-frequency modular designs offer considerable energy savings compared to 50Hz chargers. This is because the management system switches off modules as the battery charges. In this way, each module always operates at its optimum loading and efficiency. Besides the energy savings, charging time can also be reduced by up to two hours. NexSys chargers are designed to reduce energy consumption by up to 35% for TPPL batteries versus other lead-acid types.
Matching battery and charging systems ensure that the benefits of integration are attained. This approach maximises energy efficiency and battery life benefits while eliminating the potential for overcharging.
There is also an on-board charger option available for class III lift trucks: NexSys COMpact onboard chargers offer the maximum charging flexibility as they make opportunity charging easier by merely plugging into an AC socket. Embedded devices, software systems and Bluetooth communication capability enable optimum charging and precise monitoring.
Optimisation through monitoring
It is advisable to choose a partner that has a holistic approach to power management as well as an exemplary track record in battery technology. Battery and charging solutions should not demand a change to operating models. Instead, a solution should be found that optimises the operation.
Some service providers like EnerSys offer monitoring packages, including cloud-based applications. These provide deep insights as well as recommended actions for improved performance. Dashboards can be made available inside the vehicle to make drivers aware of critical parameters.
Traditional lead-acid and Li-ion batteries have some limitations, which TPPL batteries can resolve. Solutions like NexSys Core and NexSys Pure batteries designed by EnerSys offer the advantages of lower maintenance, maximum charging flexibility and long service life. TPPL technology provides a lower TCO than the alternatives, therefore, offering materials handling vehicle operators an opportunity to increase profit margins.