Electric vehicle batteries continue to cause public concern across several fronts. There is a small possibility of an EV battery catching fire in a confined parking basement, or car ferry. Popular opinion lays this chance at the door of LFP chemistry. However, when we compare NMC versus LFP EV fire risks, we may come to a different conclusion.
Comparing NMC and LFP EV Battery Chemistry
There are two main types of electric vehicle batteries in common use today. These use either nickel manganese cobalt oxide (NMC), or lithium iron phosphate (LFP) chemistry. Econo Times reports that while the NMC option costs less, it is more likely to overheat and cause a battery fire.
Their survey suggests that some 90% of electric vehicles in America, Europe, and Asia use NMC batteries. They say that manufacturers favor them, although they are ‘more prone to thermal runaway, making them a major safety concern’.
The news channel went into some detail to compare NMC versus LFP EV fire risk profiles. They analyzed twenty-four studies to access data concerning their heat release rates (HRR) at single cell-level. Although they accepted that reality was more complex with multi-cell batteries.
How the Econo Times Lined Up the Relative Fire Risks
The researchers were able to reach several interesting conclusions, despite the data being at single-cell level:
- Nickel manganese cobalt oxide (NMC) displayed relatively low heat release rates (HRR) at lower capacities. However, the heat rate spiked dramatically at capacities above 100-kilowatts.
- By contrast, lithium iron phosphate (LFP) batteries had a more consistent heat release rate pattern. This did not reach the level of high capacity nickel manganese cobalt oxide.
- The state of charge influences the power that both battery types release during a fire. Intensity remained stable from 0% to 75% charge, but at full charge, fire strength surged. This reached 31 kW/Ah for LFP, and 38 kW/Ah for NMC batteries respectively.
The Econo Times team suggested that, “NMC batteries pose greater fire risks at higher capacities, especially when 100%-charging. This emphasizes the need to consider battery type and capacity, when assessing electric vehicle safety especially for larger [battery]packs”.
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