Lithium-ion battery systems
Large lithium-ion battery systems provide power to electric vehicles, computer data centers, commercial and residential energy storage systems, and other heavy-duty applications. Battery technology and applications are rapidly evolving and so are the risks associated with large scale battery manufacturing, distribution, servicing and use.
Safety depends on our ability to recognize hazards and take precautions. To help provide safety knowledge keeps pace with the evolution of these battery systems across the workforce, ULTRUS™ Learning has prepared extensive courseware catering to individuals that work with lithium-ion batteries, along with these general guidelines.
Hazards and precautions
The process that produces electricity also produces heat. Lithium-ion batteries are sensitive to elevated temperatures and contain a flammable electrolyte solution. If the electrolyte escapes from the battery and is exposed to an ignition source, fire and/or explosion can occur. Fires can be difficult to extinguish, and they burn extremely hot; hot enough to melt metal and cause a building to collapse.
Thermal runaway incidents are significant fire and explosion risks. This is when a lithium-ion cell enters an uncontrollable, self-heating state. Understanding how thermal runaway incidents happen helps us to prevent them from happening and minimize their effects.
Thermal runaway reactions can generate elevated temperatures, fire, and the ejection of gas and shrapnel. Smoke and vent-gases from a lithium-ion battery fire present inhalation health hazards. Violent cell venting is characteristic of thermal runaway incidents. The intense heat can lead nearby cells into thermal runaway.
Batteries store energy, so there can also be electrical safety concerns. A thin separator film prevents direct contact between the cathode and anode inside of batteries. The thinness of the separator makes it a failure point in the event of a manufacturing defect or damage during handling and use. When this separator fails, an internal short-circuit can occur.
Heat produced by short-circuit incidents can cause thermal runaway. Potential causes of short circuits include mechanical abuse (drop, crush/indentation, impact, shock, vibration), process issues (contamination, burrs, tab or electrode misalignment, bad welds, loose parts), severe environments (abnormal temperature, pressure), unsafe design (improper separator), and progressive internal damages due to improper charging and discharging.
Charging and discharging a cell beyond its specified safe limits can lead to internal damage, overheating and thermal runaway. High-rate charging should be avoided in higher temperature conditions to avoid overheating. Over-discharging a cell below its specified endpoint voltage can also result in internal cell damage that increases the likelihood of thermal runaway.
Damaged lithium-ion batteries have greater potential to short-circuit and an increased fire and explosion risk. Therefore, batteries should be certified to meet industry safety and performance standards.
General lithium-ion battery systems safety guidelines
Prepare your workspace
External short-circuiting happens when positive and negative electrodes make contact directly or through mutual contact with a conductive object. One way to avoid short circuits is to work on a non-conductive surface. Remove conductive items that might drop onto batteries while you work. Use insulated tools. Move unnecessary combustibles from the charging location.
Wear personal protective equipment (PPE)
Electrically trained and qualified personnel must assess risks and take precautions before working on hazardous-voltage systems (e.g., 100 Volts DC), but heightened electrical safety precautions are needed in all situations. Wear PPE appropriate for the hazards present, such as electrical hazard-rated footwear and gloves. Safety glasses and gloves are needed if the battery is damaged or leaking. Respiratory protection may be required in some cases.
Respect electricity
Energy stored in batteries presents an electrical shock hazard after associated equipment has been turned off. According to OSHA, 50 volts is considered hazardous voltage and requires a qualified person to follow electrical safe work practices. OSHA does not provide separate limits for AC and DC current, but NFPA 70 and 70E standards from the National Fire Protection Association do provide separate limits.
Safely package batteries
Store batteries in the original packaging. Protect battery terminals by covering them with electrical tape or placing them in separate bags or containers to avoid external short circuits.
Safe handling
There are greater forces involved with dropping, mechanical shock, or vibration of large batteries. Large batteries should have handling procedures from the manufacturer that need to be followed in order to prevent damaging incidents, such as using lift cranes or other equipment for installing and handling these batteries.
Do not overheat
Store batteries in a cool, dry, well-ventilated area at or below 30 °C (86 °F) and within the manufacturer’s minimum and maximum storage temperature.
Charge according to instructions
Use chargers specific to the battery type. Follow the manufacturer’s instructions for charging.
Inspection
Fires and explosions are avoidable through early identification of damages.
- External damage includes deformed, dented, or broken parts, melted plastic, signs of corrosion and frayed wires.
- Internal damages are indicated by hissing, crackling, or popping sounds; rattling loose or dropped parts; visibly swollen cells; heat; smoke; or an odor of battery electrolyte. Batteries that will not accept a charge or provide power indicate possible internal damage.
Damaged batteries
Spent or damaged batteries are hazardous waste and require special precautions and training when transporting for recycling or disposal. The disposal of large batteries is tightly regulated. Follow the manufacturer’s safety and disposal instructions.
Incident preparedness and response planning
A pre-defined emergency plan should be in place to tackle damaged or overheating lithium-ion batteries. Pre-plan with the local fire department so first responders understand the technology, hazards and potential risks associated with batteries.
Only trained and qualified personnel should attempt to fight a battery fire, and they must discontinue efforts and leave the area if smoke is quickly filling the room, the fire is not contained, or they cannot fight the fire without respiratory protection. Battery fires beyond the initial stages are extremely dangerous and require PPE, such as a self-contained breathing apparatus and heat or fire protective gear.
When a fire begins, it may be safe for qualified workers to remove the equipment from the power source then use a multi-purpose, dry chemical extinguisher. Extinguishers will not fully extinguish a lithium-ion battery fire once thermal runaway begins. If other cells are at risk of becoming involved, then it may be advisable to flood the area with water to cool batteries and slow or prevent a cascading involvement of nearby cells. Water may not extinguish the battery fire, but it will cool the adjacent batteries and control the spread of fire.
Follow Safety Data Sheet recommendations for first aid. Chemical exposures require moving someone to fresh air and flushing their eyes and skin. Contact with energized electrical sources can cause electrical shock and burn injuries, which could require cardiopulmonary resuscitation and defibrillation. Internal injuries are not always obvious, so seek qualified medical attention.
Lithium-ion battery safety training
Special advance planning is needed to provide personnel with up-to-date training and the ability to recognize hazards and take precautions that will prevent or minimize the damage associated with lithium-ion battery incidents.
This article has provided an overview of many topics presented in UL Solutions' lithium-ion battery safety training. UL Solutions provides a wide range of web-based, licensable and customizable safety training courses for both large- and small-format battery systems.
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