Cold storage facilities have always been a punishing place for flooded lead acid batteries. Cold-induced power losses and charging complications can combine to slash battery capacity and life; flooded lead acid batteries cannot last as long in cold storage applications as they do in warmer material handling environments.
Unfortunately, current industry trends are exacerbating these challenges. The rising height of warehouse racking and the 500-inch vertical reach of the latest lift trucks are placing even greater power and throughput demands on cold storage batteries. Simply put, today’s cold storage facilities need batteries that can provide more power, charge faster and last longer, all with less maintenance.
It’s a tall order, but thanks to recent battery technology advances there are more cold storage power options than ever. And much like lift trucks that have modifications to handle cold and condensation such as enclosed motor drives, rust inhibitors, stainless steel components, special freezer oil, heaters and more, these newer batteries have features that make them well-suited for sub-freezing work. But before weighing the relative benefits of these newer technologies, it’s worth considering why the cold is so hard on conventional lead acid batteries.
Flooded Batteries vs. Freezing Temperatures
In simplest terms, cold temperatures slow down the movement of molecules, including those that make up a battery’s electrolyte. Low temperatures increase the electrolyte’s viscosity, causing it to thicken and move more slowly through the pores of the active plate, limiting the chemical reaction required to power the vehicle. Corresponding power losses can range from 20% to 60%.
For example, a fully charged flooded battery with an internal temperature of 32°F will deliver just 75% of the power it would at a room temperature of 77°F. It’s why batteries designed to run for eight hours in a warm warehouse may only last four to six hours in cold storage facilities.
These battery run-time reductions can make it harder to maintain proper run, charge and cool cycles, leading to a vicious cycle of undercharged and prematurely swapped batteries. Cold internal battery temperatures also affect charge acceptance rates. When a battery’s internal temperature drops below 40°F, its voltage will appear higher than it really is, causing battery discharge indicators to display an incorrectly higher battery power capacity. Chargers will also read voltage levels as higher than what they are and shut down prematurely.
Despite these difficulties, the majority of cold storage facilities do operate very successfully with flooded lead acid batteries. Factoring in their reduced run times is a must and working with a battery professional to assess and meet total amp hours requirements can be key. A battery changing system (BCS) can also help, as it simplifies charging and battery selection and can analyze power usage to optimize battery fleet size.
Of course, even with a BCS and a properly sized battery fleet, flooded lead acid batteries are maintenance-intense compared to newer battery technologies. And just like distribution centers (DCs) and warehouses with warmer environments, cold storage operations want to manage their business, not their batteries. Fortunately, they now have several lift truck battery options to consider that eliminate time-consuming maintenance such as watering, equalizing, changing, or cleaning, even as they perform better in the cold.
Lithium-ion Batteries
Lithium-ion (Li-ion) batteries are very well-suited for 24/7 facilities with high amp-hour demands. Their high charge acceptance rates enable efficient opportunity charging that can end the need for battery changeouts and battery rooms, giving facilities more space-saving opportunities and floor plan flexibility.
Li-ion batteries do exhibit some power capacity loss in the cold, but it is much lower than that of flooded lead acid batteries. Therefore, Li-ion battery runtimes and lifecycles are much longer.
While the expense of converting to Li-ion lift truck batteries is higher than flooded lead acid batteries, over the long-term, Li-ion battery total cost of ownership (TCO) could make them a better option.
Thin Plate Pure Lead Batteries
For multi-shift cold storage operations with lower amp-hour requirements, thin plate pure lead (TPPL) technology can often provide a “just-right” Goldilocks solution that balances power, maintenance and budget demands. A closer look at TPPL battery design helps explain why.
TPPL batteries feature 99% pure lead plates that are much thinner than those in conventional lead acid batteries. Thinner plates mean more of them can fit inside the battery; more plates deliver more power in 30% less space than an equivalently sized flooded lead acid battery. The greater plate surface area also maintains more energy and more power during peak load periods.
Additional pure lead plate surface area also minimizes the effects of increased electrolyte viscosity, allowing TPPL batteries to perform in temperatures as low as 12°F. TPPL batteries also have high fast-charge rates that enable opportunity charging and can eliminate battery changeouts. Ultimately, TPPL batteries offer almost the same virtually maintenance-free experience as Li-ion, but for roughly half the upfront cost.
Which Technology Is Best For You?
So how can you determine which battery makes the most sense for your operation? First, by quantifying exactly how much power your lift truck fleet is using and your associated costs. It may sound like a complicated prospect, but there are battery professionals that can help by conducting an on-site power study of your fleet and facility. Proprietary consultative tools, such as modeling software, are available to make collecting and quantifying the necessary power, fleet and facility data a manageable and effective process.
A thorough power assessment should weigh multiple factors, including vehicle models, shift schedules and amp-hour requirements. Any on-site power study should also compare battery chemistries, including charging times and costs, and consider other impacts on TCO. A thorough site survey can also reveal operational challenges that are driving current operating costs.
In the end, the more cold data you can muster, the more likely you’ll be able to quantify which battery chemistry, or even combination of chemistries, is best for your vehicle fleet.
Jarrod Smith is the Southeast district manager at EnerSys, a provider of stored energy solutions for industrial applications. He has been in the material handling industry for over 20 years and helped design and launch the EnerSys EnSite modeling software.
