Safety of NAS batteries

NAS batteries have obtained the certification based on stationary storage battery safety standard UL 1973 (cell and module level) and a test report based on UL 9540A standard*, which is to verify batteries and storage battery systems fire risk, for confirming compliance with its evaluation criteria (cell, module and installation level) through the evaluation program of UL Solutions, a global independent safety science company.

* NAS batteries container type (including cells and modules on mounted) are covered .

Cell design

Hermetically sealed casing
High temperature ignited short-circuit current suppression system

Module design

Each cell is wound with insulation sheet and heat and corrosion resistive sheet

Sand filling

  • Self extinction in case of fire
  • Absorption of leaked active materials


  • To prevent short-circuits

Thermal enclosure

  • To prevent the leakage of active material
  • To absorb the external physical shock

Safety tests

In designing the NAS battery, NGK placed safety in paramount importance. The safety of NAS batteries has been proven in testing by NGK and third-party authorities and from decades of field experience. NAS batteries also comply with CE Marking requirements which are essential for exportation to Europe.

Test Test Result
Fire exposure < Put module in fire >
No leakage. No fire. Safety confirmed.
Submerge < Submerge module at operational temp >
No leakage. No fire. Safety confirmed.
Drop < Drop module at operational temp >
Module enclosure was damaged but no damage to battery cells. No leakage. No fire. Safety confirmed.
Short circuit < Short circuit module >
Circuit was opened by internal fuses.
No leakage. No fire. Safety confirmed.
Self-extinguish < Ignite one battery cell inside module >
No expansion of fire to adjacent battery cells.
No leakage. No fire. Safety confirmed.
  • *NAS and the NAS logo are trademarks of NGK INSULATORS, LTD., registered in the U.S. and other countries.

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