Li-Ion Safety in Battery Plants
When setting up a new Li-Ion battery assembly facility, there are several fire safety & environmental considerations that require detailed planning during the facility design phase.
Below are a few pointers taken from a recent automotive plant D&B project for the assembly of cylindrical cells into PHEV/BEV battery packs.
Avoidance of Waste
Several initiatives can be employed on site to reduce the volume of module/pack level waste streams. These generally fall into four categories:-
Battery Re-pair (Control electronics failure)
Battery Re-manufacturing (Cell failure)
Battery Re-purposing (Pack state of health failure)
Battery Re-Cycling (Battery cells no longer hold state of charge)
Provision of facilities to accommodate the above stages can significantly maximise reuse of otherwise discarded assets that still contain value.
Fire Safety Considerations
Identifying your high-risk assembly operations & respective probability of failure is key to safeguarding business continuity and ensuring personnel safety.
Typically, activities that involve welding, end of line testing and load testing of the modules/packs introduce potential pathways that can result in cell puncture and subsequent thermal runaway if not carefully controlled.
Emergency Planning
In the event abnormally high temperatures are identified at the component level during high-risk operations. Rapid action needs to be taken. Various strategies can be employed including:-
Cell ejection to flameproof receptacles containing layers of expanded glass granulate or vermiculite, offering a lightweight alternative to sand. (Cell level)
Automated gantry crane removal to a Liquid N2 (LN2) + CO2 dispensing booth. (Module level)
Manually-closed / self-closing fire rated 'coffins' placed at conveyor eject points, enclosing the suspect component & providing valuable time for transport to a safe quarantine location. (Module level)
Provision of internal / external insulated quarantine booths accessible via AGV or designated emergency FLT. (Pack level)
Quarantine of Suspect Components
Quarantine facilities can be built on-site at a safe distance from the building, providing multiple bays ready to accept suspect components.
We prefer the use of low-cost 'sacrificial' buildings that allow for safe storage whilst further monitoring and assessment takes place. Such buildings are typically of steel frame construction with chequer plate reinforced walls and gates, plus metal sheet roofing to provide a level of weather and blast protection without putting your assets at risk.
When safe to do so - visual, thermal & functional assessments can be undertaken to categorise quarantined components into four categories:-
Hazard, Critical, Non-Critical & Functional.
The latter two categories signal the opportunity for removal and storage in a designated area ready for off-site transportation in preparation for advanced recycling.
Storage and Transportation
High CapEx shelved-storage containers are available on the market for a variety of battery sizes. They typically include fire rated insulation, ATEX rated HVAC and complex fire suppression & alarm systems.
By implementing quarantine & battery assessment processes as described above, significant cost savings can be realised with de-rated container facilities, utilising design features such as shatter proof viewing windows, roof sun reflectors, white paint to reduce solar gain, and low/high level intumescent sealed louvres to enable adequate air circulation.
Transportation off-site can be facilitated with UN certified; lightweight packaging designed for re-use. Again, significant cost savings can also be realised at this stage via the processes described - essentially down-grading the transportation compliance requirements as set out in the ADR regulations.