Using electric forklifts in cold storage environments traditionally presented a unique set of challenges due to the extreme, often sub-zero temperatures. The harsh conditions could negatively affect equipment, operators, safety protocols and maintenance routines.
With advances in charging technology and the transition by many operations from lead-acid batteries to lithium-ion batteries, one of the common pain points in these applications—charging forklifts without affecting productivity and equipment—is becoming less of a challenge.
Challenge of charging in cold storage
Charging forklifts utilized in cold storage environments has historically been a complex task requiring careful planning and offering suboptimal options due to technology limitations. Forklift chargers designed for use in ambient warehouse temperatures may not be rated for use in environments below freezing. In sub-zero settings, components inside the charger, including transformers, circuit boards and control systems, can operate inefficiently or even malfunction. To address this, charging stations for cold storage forklifts have typically been placed in adjacent ambient temperature areas, requiring forklifts to exit the cold storage area to be charged. The temperature changes experienced by both operators and equipment come with their own set of challenges.
Historically, forklifts used in cold storage applications have been powered by lead-acid batteries, which are not designed to operate efficiently in cold environments. Lead-acid batteries may lose an estimated 30% of their rated capacity when used in temperatures below 32°F. This means you will have just 70% of a battery’s available capacity accessible for actual runtime. Consequently, even a new battery’s discharge/charge cycle life is significantly shortened. This also means shorter run times before the battery needs to be returned to the battery room to be charged.
Unfortunately, frequent transitions between cold storage and ambient temperatures, either to charging stations or battery rooms, can cause condensation to form. This condensation can lead to rust and corrosion of forklift components and affect electronic components and sensors. This can make it more difficult to maintain a forklift that frequently travels between freezer and ambient temperature environments.
Additionally, lead-acid batteries can experience an artificial spike in voltage when charging in the cold. When this happens, charging may be stopped too soon, resulting in the battery being short charged. Over time, this can affect the battery’s capacity retention and shorten its lifecycle.
Cold storage charging evolving
Until recently, these performance issues and limitations were considered part of the cost of doing business in cold storage environments. Technology innovation is changing that mindset and the approach to forklift charging for cold storage applications.
Lithium-ion batteries have become a viable alternative to lead-acid batteries, especially in refrigerated warehouses and freezers.
Lithium-ion chemistries experience less voltage drop and the batteries maintain more of their original capacity in low temperature environments. Some batteries include integrated heaters or battery management systems (BMS) that regulate internal temperature, promoting reliable operation even in sub-zero conditions.
Lithium-ion batteries are designed to be charged faster and more efficiently and are often integrated into the forklift so the battery does not need to be removed during recharge. Lithium-ion batteries may require only one hour of charging for eight hours of use. They can also be opportunity charged during operator breaks without leaving the cold storage environment and do not require a cool-down period after recharging.
Chargers represent another area of innovation. There are chargers available today designed specifically to work in cold storage environments. They feature industrial-grade components that maintain expected functionality at sub-zero temperatures. By installing chargers in the cold storage area, forklifts no longer need to move into ambient temperature areas to charge, which minimizes the risk of condensation and damage caused by moisture.
Some chargers can also communicate with BMS and battery monitors and use smart algorithms to determine battery temperature and adjust the charging rate accordingly. This avoids the potential for an artificial voltage spike when charging a cold lead-acid battery. Unexpected voltage spikes present a false state of charge for the battery and could result in overcharging or undercharging, which can reduce battery lifespan over time.
Cold storage best practices
As these technology innovations make charging forklifts in cold storage environments a more viable option, there are a few key best practices to keep in mind.
1. Consider the charging station location
When placing charging stations, ensure adequate room to properly position forklifts for charging. This can be especially important if two or more charging stations are co-located. Also consider pedestrian and operator access, location of the forklift’s charge port, the direction of travel and the available charger mounting locations.
2. Practice proper cable management
Cold and sub-zero temperatures can make cables more brittle over time, which can lead to charging failures due to connector and cable stress, even when not charging. This is more likely to occur if proper cable management practices are not maintained. Parking forklifts in the appropriate position with the cable supported helps the cables maintain their flexibility. Incorrect charging station configuration can also lead to improper cable management, which can cause undue stress on cables and connections.
3. Don’t forget about the onboard heaters
Lithium-ion batteries suitable for freezer use have onboard heaters that help ensure battery performance. These heaters typically discharge 5-6 amps per hour which means when the forklift is sitting idle and not plugged into a charger the battery charge level is dropping. This is why it is critical in cold storage applications to plug in lithium-ion batteries to the charger if the forklift is going to be idle during operator breaks or shift changes. The charger will continue to charge the battery as needed to ensure it stays topped off and ready for operation.
4. Ensure necessary operator training
Consider how changes in charging habits should be addressed in forklift operator training. Operations that make the switch from lead-acid batteries to lithium-ion and from centralized chargers to distributed charging stations must continue to remind operators that they need to modify their charging behavior, or they risk not realizing the benefits associated with these new technologies. This risk level is increased in cold storage operations.
5. Prioritize integrated solutions
The compatibility of components in your forklift power system, including the forklift itself, can offer a number of advantages. A highly integrated system can help increase uptime, reduce maintenance and parts replacement and improve safety during charging and operation. Integrated systems can also produce savings in time, money and energy consumption. Forklift compatibility is also important. During lift truck operation, an integrated power system works with the lift truck’s operating system to reliably monitor state of charge and adjust lift truck behavior to provide ample notice when charging is needed.
6. Consult with experienced providers regarding configuration
When considering adding charging stations to a cold storage environment, the knowledge accumulated by the forklift and/or charging station provider can be a great resource when consulted early in the process. Your provider can help identify the best location for the charger(s), ensure proper cable management is implemented and help you communicate best practices to your workforce to help ensure that potential productivity gains are achieved.
