Li-ion battery

Comparing Lithium-Ion and Lead-Acid Batteries

Dec. 6, 2019
Comparing the two batteries’ performance in keeping forklifts up and running seems to tilt the choice in a definitive direction.

Battery technology is evolving and taking the world by storm, offering an array of possibilities for the machines and devices that help keep our global infrastructure humming. But as the technology improves and options abound, how does one choose between traditional lead-acid batteries and the newer lithium-ion variety?

The Contenders

Lead-acid batteries have long held the largest market share in rechargeable batteries, thanks to low cost, reliability, and a lack of alternatives. They are popular for applications in which weight and space are not major concerns. Lead-acid has history on its side, having long been used successfully. But lead-acid batteries also have the lowest energy-to-volume and energy-to-weight ratios among secondary batteries. They are also quite demanding in terms of daily preventative maintenance and strict charging schedules. Neglecting this rigorous routine considerably diminishes the life of lead-acid batteries.

The main critique of lithium-ion has been cost, as the upfront purchase costs are typically considerably higher than those of lead-acid batteries. But although more costly, lithium-ion have more than twice the cycle life of lead-acid, and the highest energy-to-volume and energy-to-weight ratios among secondary batteries. This translates to more energy and weight in a smaller space.

As long as Li-ion batteries are more expensive than lead-acid, the economics of switching battery types depends on how much they are used and, therefore, on the downtime and maintenance they require. Operations where switching to lithium-ion provide a 20 to 40% reduction in the total cost of ownership include those involving a fleet of forklifts covering several shifts.

At such companies, Li-ion batteries need less time and space for charging and maintenance than lead-acid batteries. Lithium-ion batteries offer better charging options, so forklifts can be quickly recharged, at least partially, during short breaks and downtime before getting back to work. This is where companies begin to see substantial savings from their higher investments.

Batteries in the Warehouse

One company that uses forklifts, Standard Distributing Co. Inc., found that areas for charging and maintaining its lead-acid batteries were difficult to keep clean. Also, it cost money to take lifts offline for eight hours of charging and eight hours of cooling, a requirement for lead-acid batteries.

A Li-ion battery, by comparison, can be charged from zero to full power in under two hours and there is no memory effect, so quick recharges are recommended.

Lead-acid batteries can seriously degrade if recharged too often. Li-ion batteries stay in top condition regardless of how often they are recharged or what the depth of discharge is.

In April of 2019, with the help of the Eastern Lift Truck Co., Standard Distributing had figured that 12 forklifts running on Li-ion batteries could do the same job as 17 forklifts powered by lead-acid batteries, thanks to opportunity charging.

A major drawback of lead-acid batteries is that they require extensive daily maintenance in the form of watering each shift. This increases labor costs. Li-ion batteries, by comparison, require no daily maintenance.

Saving time on maintenance lets workers focus on other tasks within the business. Eliminating daily maintenance, along with the need for eight-hour charging shifts and eight-hour cooling shifts, also saves warehouse floorspace. Lead-acid batteries require a dedicated room where they are charged and stored. While charging, they emit dangerous hydrogen and sulfuric gases, so the room must be well-ventilated and kept cool.

Chargers for Li-ion batteries can be stationed throughout a facility for short or long recharging. After switching to Li-ion batteries, Standard Distributing found that the floorspace it had devoted to lead-acid battery charging and maintenance could be reclaimed; keeping the area clean, an issue of difficulty for the facility previously, was no longer a problem.

Density and Capacity

A battery’s capacity defines its run time, which reflects the current the battery can provide until it needs recharging. Power density, on the other hand, defines the battery’s maximum discharge rate. Some batteries require lower rates of discharge, but those called on to provide bursts of power need more power density.

The life-cycle durability of a battery defines the stability of the battery through repeated cycles of recharging and  discharging. Some of Li-ion battery users have noted they can replace a lead-acid battery with a lithium-ion battery with as little as 60% of the same capacity. That’s because the lead-acid battery’s maximum discharge is 80%, whereas lithium-ion batteries’ maximum discharge is 100%; they can be discharged to zero.

In addition to that disparity, the harmless quick or partial recharges of lithium-ion batteries would quickly reduce the lifespan of a lead-acid battery.

Green Operations

Li-ion batteries offer a way to create more environmentally-friendly warehouses. That’s because lithium-ion batteries are 30% more energy-efficient than their lead-acid alternatives, reducing costs and carbon footprints. Li-ion batteries do not contain toxic substances or emit harmful gasses, making them safer for the environment, the warehouse, and its workers’ workforce.

Such considerations are paramount at Standard Distributing, where having a clean and efficient warehouse is essential for both the beverages it handles and the company’s green policy. It also means a leaner operation overall, using just 12 forklifts instead of 17.

The company’s new Li-ion battery-powered forklifts also provide safer working conditions. Workers no longer have to remove heavy batteries to replace them with freshly charged batteries; acid spills are no longer a risk, nor the possibility of inhaling toxic gas fumes during charging.

Additionally, with lithium-ion batteries in forklift trucks, battery don’t need to be disposed of as often. OneCharge, for example, collects Li-ion batteries it has shipped to customers when they reach the end of their useful life, disassembles them, recycles the metal cases, disposes of the electronics, and sends the li cells back to the manufacturer for repurposing or proper disposal.

There are many points of analysis to consider in selecting batteries for electric forklifts. However, in many cases the clean and efficient operation provided by Li-ion technology may be the answer for material handling businesses as they improve the performance  of their forklifts and grow the bottom line.

Maxim Khabur is marketing director of OneChange Inc.

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