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Sigma Cells

Published on 18 December 2019

All-in-one inverter, charger and advanced battery management system for enhanced e-mobilitys


  What is Sigma-Cells?

Sigma Cells, Leti’s switched cell technology, is revolutionizing the world of batteries for e-transportation revisiting the traditional architectures and taking the multi-cells power source as a key advantage to bring a disruptive solution featuring:
  • Improved power conversion efficiency
  • Fast charging at no additional cost
  • Less bulky and lighter batteries
  • Reduced pollution: currently, if only one cell fails, the entire battery is down
  • Contraintless electrical vehicle architecture
  • Simplified diagnostic & maintenance

Sigma Cells allows smart use of battery cells—the battery brains, by:

  • Ensuring continuity of service in the event of sudden cell failure by finding an alternative “safe route”
  • Leveraging the “best” cells at a time to ensure longer autonomy and a power reserve


Sigma Cells is designed for e-mobility applications regardless of the power size: for example e-cars, e-bicycles, e-buses, etc.

Sigma Cells can also be leveraged for storage applications, among others:
  • Network regulation
  • Server supply
  • Nomadik power banks
  • Power tools supplies
  • Autonomous building…

   What's new?

With e-mobility coming down the road, Sigma Cells addresses tomorrow’s massive demand for power conversion and efficiency. Here is what’s new:
  • Inverter function: provides a direct motor drive from the battery pack providing a waveform in line with the motor speed, torque and power
  • Integrated fast charger: bidirectional system (current and voltage) enabling a direct recharge on the electrical network
  • Advanced BMS with individual and continuous access to any cell unit:
    • reducing SoC and SoH error estimation by a factor 2
    • improving autonomy of 20%
    • improving life time of 15%
  • Enhanced performances thanks to native low voltage switching (~3.6V) compared to a classical inverter switching the full battery pack voltage (~400V):
    • reducing drastically the switching losses by 100
    • reducing the need for cooling
    • reducing drastically the CEM emission by 100

   What's next?

Leti is working hand-in-hand with industrials to prepare the upcoming e-mobility boom. Researchers are currently working towards enhanced systems and dedicated hardware and software for the automotive industry.


 14 patents

 “Battery Having a Brick Architecture Including Cells Arranged in Series or in Parallel”, 2012, G. Despesse, Patent US 2014287278, CN103782413

 “Battery with Individual Cell Management”, 2011, G. Despesse, Patent US 20140015488, JP2014512636

• “Battery Monitoring System Using Switching Battery Cells - Paper”, G. Despesse, S. Lechat Sanjuan, S. Gery, Conf. ASTech-RITF, Paris, 2012
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