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Smart cell management system for future batteries

Electronics
Energy / Utilities
Compelling a hardware/software solution for a future generation of Battery Management Systems (BMS) based topology and on the concept of smart-cell: the battery cell (hardware) plus its dedicated controlling electronics (software). The solution uses online Electrochemical Impedance Spectroscopy (EIS) and intelligent switching architecture to provide accurate state estimation, lifetime extension, improved safety, and easy second-life repurposing.

Issue

Today’s battery management systems (BMSs) are based on a master/slave architecture, voltage/current measurements and passive balancing. Battery packs are complex systems where electrochemical reactions happen at cell level and determine the pack performance, ageing and safety.

Such BMSs present some issues:

  1. Voltage and current do not relate accurately to the inner electrochemical reactions of Li-ion cells;
  2. They cannot track the aging evolution of each single cell (i.e. SoH);
  3. They cannot estimate the inner temperature of each single cell;
  4. They do not implement operation margins to ensure an adequate level of safety reducing the battery's performance;
  5. There is a limited degree of freedom in controlling each cell according to its state;
  6. passive balancing fails to balance cells that have aged differently, reducing the pack lifetime (pack limited by its weakest cell);
  7. They do not trace/store the state of battery cells, hindering reuse and recycling.

 

Solution

We have developed a hardware/software solution for Battery Management Systems (BMS) based on the smart-cell concept: the battery cell (hardware) plus its dedicated controlling electronics (software). The solution provide several advantages:
  1. Accurate state estimation with EIS and dedicated battery models. Validated RMSE <5% in wide range of SoCs (5/95%) and temperatures (-10/40°C);
  2. Novel active balancing method able to correct up to 50% SoC imbalance (without dissipation) and keep cells' SoHs uniform.
  3. Battery lifetime extended by more than 20% thanks to a combination of sensing (EIS) and acting (switching) capabilities.
  4. Increased safety, thanks to combination of sensing (EIS) and acting (switching) capabilities.
  5. Savings on the diagnostic assessment for second-life repurposing. 

Our BMS solution is based on a fully-decentralised architecture, with these features:
  • Distributed intelligence: each battery cell is equipped with its own cell management system (CMS);
  • Electrochemical Impedance Spectroscopy (EIS) at cell level without external equipment;
  • Capability to switch each single cell in/out to modulate the usage of each cell;
  • Physically-based models to estimate battery states (SoC, SoH, etc.).
  • Wireless communication to reduce wiring
  • Cell traceability to store relevant information at cell-level.
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