Is there a significant (safety) advantage of lithium-iron-phosphate batteries over lithium-ion batteries? Especially at high temperatures?

The FLIR K series use lithium-ion cells using the very latest NMC technology. (Lithium Nickel Manganese Cobalt Oxide - LiNiMnCoO2).

The cells we use for the FLIR K series are produced by one of the top three manufacturers and are of the highest quality. The same manufacturer also produces lithium-ion-phosphate cells and these will also be of a very high quality.

The lithium-ion manufacturers are very focused on safety, and this attitude is applied to the development of all cell types.

There are different lithium-ion cell chemistries, and different chemistries give different cell behaviour. This different behaviour allows lithium-ion cells to be used in very different applications.

A couple of examples:

  • Some cell types can provide very high discharge currents, but have lower cell capacity and voltage. These are ideal for power tools.
  • Some cell types have high capacity but much lower discharge levels. Ideal for laptops, etc.

All cells are extensively tested to the UL1642 standard to prove the bare cell safety. (Cells are submitted to extensive and abusive tests including high temperatures.)

The issue we see for using lithium-phosphate for the FLIR K series is the low capacity (energy density), which is approx. 50%. Consequently, you need double the number of cells for the same energy density as NMC.

The cell voltage of lithium-phosphate is only 3.2 V where the NMC is 3.7 V (used in all other handheld FLIR cameras).

General comments

  • 85°C/185°F – for short periods of time the device will operate normally. For longer times you will see very slightly higher self-discharge. If the battery pack is used regularly at 85°C/185°F, you may see some slight reduction in battery pack life time.
  • 150°C/302°F – The battery pack and specific cell is designed with a number of safety features. At this temperature there is a CID, Current interruption device. This CID Open circuits the cell and opens a vent to release any pressure. Expect no leak, no deformation, no fire. Battery pack not operating. This is tested in UL1642 as the hotbox test.
  • 260°C/500°F – The plastic housing material is very close to its limit and will likely disassemble.
    There is still no risk for fire and explosion.

Note! The battery itself is protected against heat by the housing and the gloved hand.

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