LFP or NMC: which battery chemistry is safer at home?
Lithium iron phosphate and nickel manganese cobalt cells behave differently in a fire. What a 2024 study measured, and where to place a battery either way.
The two common chemistries
Most power stations and balcony batteries sold today use lithium iron phosphate cells, often written LFP or LiFePO4. Older and lighter models often use nickel manganese cobalt cells, written NMC. LFP stores less energy per kilogram, so the units are heavier, but it is more stable when overheated and usually lasts more cycles.
What happens in a fire
A 2024 study by Bugryniec and colleagues compared the gases released when cells fail. NMC released about ten times more carbon monoxide per kWh than LFP, about 172 against 19 grams. LFP, on the other hand, released more than ten times as much hydrogen fluoride per kWh, 50 to 100 grams against less than 10. So LFP is less likely to go into violent thermal runaway, but its smoke is still dangerous. Neither chemistry is harmless.
Where to put a battery
Do not place any lithium battery in a hallway or staircase you would use to escape, or in a bedroom. Choose a dry place with some air around the unit, away from heat sources and things that burn easily, and within reach of a smoke alarm. Charge only with the charger and cables from the manufacturer, and stop using a unit that swells, smells or gets unusually hot. When you compare models, prefer LFP and look for an independent safety mark rather than a claim in the advert.