General information
Whether you are running one small electric-powered industrial Truck (PIT), such as a forklift, or a large fleet, your facility needs PIT charging stations, either dispersed or grouped in a battery charging room. A question frequently raised by our clients is, how to make a charging station or room practical, compliant, and safe with lithium-ion (Li-ion)batteries? This question is of even greater importance given the popularity of these batteries. It is generally agreed that Li-ion batteries are set to displace lead-acid batteries in the medium term as they offer several benefits that make them the preferred choice among clients, such as short charging times, being maintenance free, etc.
The context
While fire protection knowledge around Li-ion batteries is starting to become more comprehensive, particularly regarding assembly or automotive manufacturing, the understanding of how Li-ion batteries behave in cars and trucks in real-world conditions is far different. This is also true for PITs. Electric vehicles are subjected to many tests defined by local authorities and/or the Society of Automotive Engineers (SAE). SAE International published the SAE J2464 standard, which establishes a range of abuse tests for rechargeable energy storage systems (RESSs) for electric or hybrid vehicles. These tests determine their response to conditions or events beyond their normal operation and are mechanical (vibration, acceleration shock, static compression), electrical (short-circuit, overload, full discharge) as well as thermal (exposure to fire, thermal shock, charging cycle at high temperature). Unfortunately, similar testing is not required for PITs. This lack of testing creates a lot of confusion and fear in the knowledge that this type of equipment is being used in industrial settings.
Few key numbers:
According to Fortune Business Insights, by 2026 more than 2.2 million forklift trucks will be in use globally, with a significant share of these forklifts using Li-ion batteries.
Over 4 million robotic vehicles are expected to be installed in over 50,000 warehouses by 2025, according to ABI Research.
The context
There are three primary causes of fire events in Li-ion batteries:
Thermal event: External heating associated with a failure of the ventilation system or im-proper design of the battery
Electrical event: Internal short circuit due to internal cell defects, overvoltage charging or a defect in the internal resistance
Mechanical failures: Physical damage to a cell which may have occurred during the manufacturing or installation process, as well as damage caused by vibration or expansion
PITs, such as forklifts, are very susceptible to mechanical failures due to the environment in which they are used. Furthermore, they are used in buildings where the temperature can vary greatly from one season to another. These events can lead to thermal runaway, which is a chain reaction leading to a decomposition reaction of the cell that spreads to adjacent cells. Once thermal runaway starts, it is difficult to stop and can result in the following:
Exothermic reaction with heat release
Release of flammable and toxic gases. The gases are generated within the cell enclosure before venting.
Intense fire because the cell casings are primarily constructed of plastic.
Even after the fire has been extinguished, stranded electrical energy may be observed, which can result in reignition. It is a unique hazard that can make an incident unsafe for long periods (from hours to days to weeks). Thermal runaway can cause re-ignition long after the fire has been fully extinguished. Reignition always involves an external electrical, thermal or mechanical stimulus, which is the cause of the thermal runaway. Based on loss history, the batteries seem not to reignite on their own once they are properly cooled. Therefore it is important to understand the differences between cooling and extinguishing. PITs can come in normal or quick/fast charging types. The difference is mainly due to the amperage available, with quick/fast charging implying a higher power needed for recharging. The main issues observed with quick charging stations is that some cells in a quickcharging battery pack may become overcharged due to inconsistency among the cells and adds stress, even if the battery is designed for such a purpose. This can result in thermal runaway.
Recommendations
The following recommendations can greatly reduce the potential for property damage and the resulting business interruption. As soon as the use of PITs powered by Li-ion batteries is being considered, contact your Risk Manager to discuss. The following recommendations should be discussed on a case-bycase basis depending on whether the PIT manufacturer has performed abuse testing like those described in SAE J2464. It is important to note that the literature regarding the fire behavior of Li-ion batteries is still not comprehensive. The following recommendations can greatly reduce the potential for property damage and the resulting business interruption. As soon as the use of PITs powered by Li-ion batteries is being considered, contact your Risk Manager or Elen Risk Consulting. The following recommendations should be discussed on a case-by-case basis depending on whether the PIT manufacturer has performed abuse testing like those described in SAE J2464. It is important to note that the literature regarding the fire behavior of Li-ion batteries is still not comprehensive.
Battery charging room or station? Construct a battery charging room as soon as there are more than 10 PITs at your location. Why does Elen Risk Consulting propose this threshold? Installing charging stations all over a facility can become a nightmare to manage from a loss control perspective. There are requirements regarding the space separation between charging stations and any combustible material, and this can become difficult to police when there are many charging stations in different areas. It is our experience that it is necessary to create a dedicated battery charging room when you have more than 10 PITs.
Battery charging room
Battery charging room with Li-ion batteries Battery charging room with lead-acid batteries The requirements for creating a battery charging room are well established with regards to PITs driven by lead– acid batteries. Should these requirements be the same for PITs driven by Li-ion batteries? The answer is yes, but there are additional requirements specific to Li-ion batteries listed below in Recommendation No. 4.
a. Install fire detection device (smoke and heat).
b. Install mechanical ventilation ideally ducted outside. If ventilation is common to other rooms, provide interlocked dampers to prevent contamination of other areas in the event of fire. c. Ensure the room is segregated from other areas with a fire rating of at least 1 hour, but ideally 2 hours.
d. Maintain a minimum distance of 0.9 m (3 ft.) between two charging stations within the room. This ensures that the battery is always accessible to operators.
e. Prohibit the use of combustible material in the room (combustible pallets etc.).
f. Equip the battery charging station or room with fire extinguishers suitable for use on electrical fires.
g. Install sprinkler protection designed to provide an Ordinary Hazard Group 1 density in accordance with the latest edition of NFPA 13, Standard for the Installation of Sprinkler Systems. There are various ongoing discussions in the fire protection community to determine what sprinkler densities are adequate for battery charging rooms. Recent Factory Mutual fire tests demonstrated that a fire involving a single rack of Li-ion batteries was controlled by a sprinkler system with a relatively low density. The most challenging issue is not the fire itself, but the firefighter response and the post-incident management.
3. Battery charging station
a. Remove all combustible materials located within 2.5 m (8 ft.). It is important to note that local requirements may require a greater distance. This requirement is for the battery charging station and associated PIT, including the area above the charging stations. Install mechanical protection or floor markings around this 2.5 m (8 ft.) perimeter.
b. Do not place the battery chargers within a storage rack.
c. Do not use wooden pallets (or other combustibles) as a housekeeping pad for charging stations.
d. Never install battery-charging stations on or near combustible construction materials (combustible sandwich panel).
4. Specific requirements for both battery charging stations and rooms using Li-ion batteries
a. Ensure the battery management system (BMS) of the batteries complies with the current requirements under the P2686 - Recommended Practice for Battery Management Systems in Energy Storage Applications. The capacity of the battery to anticipate a possible fire does not lie in the cell itself but in the BMS. The BMS technology varies in complexity and performance.
b. Inform the fire service about the presence of PITs powered by Li-ion batteries so that they can plan accordingly. Considerations for the fire service should include the following:
l. Since toxic gases are released during a thermal runaway event, the fire service will likely need SCBA gear.
ll. An infrared camera should be used to identify hot spots and potential areas of reignition
lll. Submerging batteries in water (preferably outdoors) after they burn has proven to be effective at cooling the batteries and neutralizing the thermal threat..
c. Maintenance plan
l. Inspect the battery charging contacts on a weekly basis for any signs of arcing. Take corrective action when signs of arcing appear.
ll. Conduct infrared scanning on an annual basis for all electrical components associated with the charging stations.
III. Establish a battery replacement program for aged batteries. Review the battery replacement program regularly and include, at a minimum, the following components:
1. Regular monitoring of the state of health of batteries which is generally available through the BMS.
2. The Original Equipment Manufacturer (OEM) design life expectancy of the batteries. This will be based on the number of years and the number of cycles that the battery is expected to perform adequately. After this point, the battery’s performance will deteriorate and the likelihood of thermal runaway will increase.
Interlock all equipment to stop operating upon actuation of the fire alarm system (activated upon sprinkler or fire detection).
Select batteries that are NEMA rated IP54.
Some clients decide to have both lead acid and Li-ion charging stations in the same area. This creates the potential for operator error. Therefore operating training is essential in this case.
References
Global Forklift Battery Market – Allied Market Research
Définition des bonnes pratiques dans la conception et la gestion des installations de charge de batteries (Definition of good practice in the design and management of battery charging facilities) – Ineris
P2686 - Recommended Practice for Battery Management Systems in Energy Storage Applications – IEEE SA Standards Association
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