In order to explain the engineering principles
on which the safety of Miretti explosion protected Li-Ion Batteries is based, Miretti
would like to elaborate the following comments.
In a Li-Ion battery, the internal cells might generate a dangerous explosion if they are present simultaneously the explosive material, a certain kind of rugged battery metallic box and an ignition source in the battery cells.
The Li-Ion battery may be subjected to high risk of explosion if for example it is selected a wrong chemical type for the cell or an improper mechanical construction design and distancing between the cells, thus making the thermal runaway effect more likely to happen. Miretti is selecting the type of battery for which a runaway condition should not occur.
The Ex d metallic enclosure might be of a type unable to safely resisting to the pressure generated by an explosion in the battery cells, but there are solutions to avoid the dangerous increase of the internal pressure
such as a proprietary Miretti designed explosion proof pressure release and limitation system or other Miretti proprietary methodologies studied to completely avoid the risk of letting a dangerous explosion happen.
The battery cells' ignition may be caused by different factors: failure of BMS (if not redundant), external fire, impact/penetration of foreign objects (if not protected by a rugged enclosure). Miretti is selecting the proper BMS system as well as is using the rugged Ex d enclosure against the impact and the dangerous penetration of foreign external objects. Furthermore, the standards used by Miretti such as for example UL1642, UL2580, IECEX ExTAG/539A/CD and EN60079-0, EN60079-1 include various electrical, mechanical and environmental tests, also simulating fault conditions in the system in order to ensure that a thermal runaway is not allowed to occur.
Concluding, Miretti is eliminating the above dangerous factors to obtain the battery to be safe and suitable for potentially explosive environments.
Therefore, a Li-Ion battery inside an Ex d enclosure or any metallic totally sealed enclosure (solution commonly used by vehicle manufacturers) may be dangerously explosive if the right countermeasures are not taken. Similarly to Miretti, the automobile manufactures, which integrate the battery into the metallic frame of the car in a completely sealed metal cage (to protect the battery in case of a crash accident or the external impact from an object), are taking in consideration the above-mentioned factors.
Technology and the practice go on and Miretti has developed an explosion proof solution which takes into account all the above considerations and is substantiated by previous art, experience and literature by the automotive and aerospace industry and by other explosion proof manufacturers which have already certified through a European Notified body an explosion proof battery using the Ex d method of protection.
The Ex d enclosure solution is, in Miretti' s opinion, as of now the most practically feasible explosion proof protection for Li-Ion batteries.
As most of the industrial equipment manufacturers and automotive manufactures are currently using a rugged metallic totally sealed enclosure very comparable to the Ex d typology design in order to protect the battery from object penetration, the Ex d solution appears to be the natural choice
as it does not alter the main construction concept adopted by most of the Li-Ion batteries and vehicles manufacturers and is also protective towards the impact/penetration and possible fire coming from an external impact.
Miretti company, in any case, is always conducting R&D and looking forward to developing new solutions which could be more ergonomic and compact, such as using the Ex e, Ex m and Ex i methods of protection for the Li-Ion battery; but at the state of the art of the current Li-Ion technology there are still more disadvantages than benefits.
is working with experienced testing laboratories to conduct the studies and certification of explosion proof Li-Ion batteries. One of the laboratories Miretti is collaborating with has developed a very huge experience in Li-Ion battery testing, working with the automotive industry and has been the first to write the alert letter related to the use of the Ex d protection method for Li-Ion batteries. The analysis related to the risks associated to using an Ex d method of protection have been very useful in order to develop and apply the solutions to resolve definitively the above mentioned risks.
The alert letter has resulted in looking at the Ex d solution in a different positive perspective through the push of studying more deeply the subject looking to previous art, developing new solutions and applicable technology. Miretti is willing to share its experience on explosion proof Li-Ion batteries with the various international legislative committees in order to give a possible contribution to the elaboration of dedicated standards on the explosion protection of Li-Ion batteries, which are the emerging battery technology used in the industrial vehicles.
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