Why the Korean Energy Storage System (ESS) burned themselves?

Between August 2017 and October 2019, up to 28 fires occurred at Energy Storage System (ESS).

South Korea Identifies Top 4 Causes that Led to ESS Fires

Nexceris June 2019

This week South Korea announced the conclusions from their fire investigation committee regarding the root cause for the 23 energy storage system fires that have occurred since August of 2017

  • Insufficient battery protection systems against electric shock
  • Inadequate management of the operating environment
  • Faulty Installations
  • ESS System Integration

Battery makers refute findings behind ESS fires

Thelec.kr Feb. 9th, 2020

South Korean battery makers refuted findings by a team of experts and government officials who announced on Feb. 6 that 4 out of 5 of the fires that occurred at Energy Storage Systems between August and October in 2019 were due to batteries.

The investigative team said that a variety of defects in the batteries were caused most of the fires, but battery makers LG Chem and Samsung SDI immediately issued statements denying the claims.

The two companies also found fault with the investigation itself, saying that fires did not occur in some of the reenactments. They also criticized the team for preemptively targeting batteries in the first place as the cause of the fires.

In the previous first round of investigations, there had been some consideration and analysis about the management of ESS in general, but this time, the investigation was purely focused on batteries.

The Korean Battery Chemistry

Lithium Polymer NMC battery cells are the key focus of the two leading manufacturers in Korea: LG Chem and Samsung SDI AIO.

NMC batteries are used for cell phones, electric vehicles, as well as energy storage systems.

Like other Lithium-ion polymer cells, NMC has the advantage of high energy density but with relatively long cycle life than other polymer cells.

LG Chem ESS Pack

Battery cell is claimed to be high output and high energy.

The True Cause of the Problem

NMC batteries are high energy density battery cells.

When a large number of battery cells are packed in a small space without good ventilation for each individual cell, heat will built-up particularly when they are drawn with 1C or higher discharge current.

In principle, the battery cell can handle 5C continuous discharge current with sufficient ventilation of heat. When a lot of batteries cells were packed in a close environment discharging around 1C or more current will dissipate a lot of heat.

Power dissipation is equal to the square of discharge current multiply with the internal resistance of the battery cell. (P=I2R).

When the batteries are heated up, the internal resistance will increase. An increase in internal resistance will increase the heat dissipation, which is called thermal runaway, eventually leading to the self-burning of battery cells.

Conclusion

Most of the battery system designers have little knowledge about the power dissipation of batteries and they simply based on the specification given by the manufacturers.

If safety is the utmost concern of a system particularly in an energy storage system (ESS), Lithium iron phosphate (LFP) batteries, containing Iron acting as an internal heatsink, are far safer than Lithium polymer type, high energy density, batteries such as LiCoO2, NCM, NMC, NCA.

The author has over 30 years of experience in the Lithium-ion battery industry from the laptop application, electric vehicle, to large energy storage.

To find LFP type Lithium-ion batteries, please visit everspring.net

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