The battery cell chemistry is Lithium Iron Phosphate (LiFePO, a.k.a. LIPO, a.k.a. LFP). This is a benign chemistry that is more tolerant of abuse including heating and puncture than most other lithium chemistry. Certainly much easier to control in an emergency that Lithium Cobalt Oxide (LCO) cells that are found in phones and laptops. Burning is normally slow, taking about 20 minutes to completely set alight.
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