Modular Approach for Continuous Cell-Level Balancing to Improve Performance of Large Battery Packs

Kandler Smith, Eric Wood, Regan Zane, Gregory Plett, Dragan Maksimovic, M. Muneeb ur Rehman, Michael Evzelman, Kelly Hathaway

Research output: Contribution to conferencePaperpeer-review

65 Scopus Citations


Energy storage systems require battery cell balancing circuits to avoid divergence of cell state of charge (SOC). A modular approach based on distributed continuous cell-level control is presented that extends the balancing function to higher level pack performance objectives such as improving power capability and increasing pack lifetime. This is achieved by adding DC-DC converters in parallel with cells and using state estimation and control to autonomously bias individual cell SOC and SOC range, forcing healthier cells to be cycled deeper than weaker cells. The result is a pack with improved degradation characteristics and extended lifetime. The modular architecture and control concepts are developed and hardware results are demonstrated for a 91.2 Wh battery pack consisting of four series li-ion battery cells and four dual active bridge (DAB) bypass DC-DC converters.

Original languageAmerican English
Number of pages8
StatePublished - 11 Nov 2014
EventIEEE Energy Conversion Congress and Exposition (ECCE) - Pittsburgh, Pennsylvania
Duration: 14 Sep 201418 Sep 2014


ConferenceIEEE Energy Conversion Congress and Exposition (ECCE)
CityPittsburgh, Pennsylvania

Bibliographical note

See NREL/CP-5400-61263 for preprint

NREL Publication Number

  • NREL/CP-5400-64931


  • bridge circuits
  • DC-DC power converters
  • distributed control
  • energy storage
  • secondary cells
  • state estimation


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