Modular Approach for Active Cell-level Balancing to Extend ... · M. Muneeb Ur Rehman, Regan Zane....
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Approach and Vision Proposed Integrated BMS-DC/DC System Bypass Converter Topology • Existing DC/DC and battery management system is replaced with integrated, modular BMS-DC/DC • Low-cost isolated bypass DC/DC converter modules connect each cell to the vehicle 12 V bus • 12 V load is used to differentially balance battery cells • 12 V battery is reduced in size (or eliminated) • Total system cost is lowered Phase-shift modulated Dual-Active Bridge Converter Operating Waveforms Parameter Value Input voltage 2.5 – 4.1 V Output voltage 13 – 16 V Power rating 35 W Peak efficiency 94 % Inductance, 35 nH Turns ratio, 4 Switching frequency, 250 kHz Hardware Results • Life balancing extends battery life by reducing stress on weakest cells • Range no longer limited by weakest cell in the pack • Relaxes thermal management requirements -- Passive Balancing -- Life Balancing Pack level results with life balancing control Discharge Cycle (US06 drive cycles) Charge Cycle (15 A Constant Current) • Cell-level and sub-string level DC/DC • Full pack implementation on PHEV • Long term validation tests in progress at NREL with A/B passive versus Life Balancing Team Partners The information, data, or work presented herein was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000271. Conclusion • Cost neutral integrated BMS-DC/DC system replaces existing BMS and HV-to-LV DC/DC • Life balancing leads to reduced capacity imbalance, increased lifetime, and relaxed thermal management • Range is no longer limited by weakest cell in the pack • Proposed system architecture and life balancing is experimentally validated PHEV20 air-cooled BEV75 liquid-cooled BEV225 liquid-cooled +29% +42% +45% Battery Cell bypass DC/DC Battery Cell shared bus SELECT Annual Meeting and Technology Showcase – Logan, Utah – September 27-28, 2016 M. Muneeb Ur Rehman, Regan Zane Utah State University Fan Zhang, Dragan Maksimović University of Colorado Boulder Kandler Smith, Ying Shi National Renewable Energy Lab Modular Approach for Active Cell-level Balancing to Extend Electric Vehicle Battery Pack Lifetime • Dual-active bridge topology offers high efficiency and low rms currents • DC/DC is designed for nominal li-ion cell voltage and LV DC bus for electric vehicles • DC/DC is designed with suitable power rating to enforce life balancing • DC/DC regulates output voltage and cell state-of-charge (SOC)
Transcript of Modular Approach for Active Cell-level Balancing to Extend ... · M. Muneeb Ur Rehman, Regan Zane....
Approach and Vision Proposed Integrated BMS-DC/DC System
Bypass Converter Topology• Existing DC/DC and battery management system is replaced with integrated,
modular BMS-DC/DC• Low-cost isolated bypass DC/DC converter modules connect each cell to the
vehicle 12 V bus• 12 V load is used to differentially balance battery cells• 12 V battery is reduced in size (or eliminated) • Total system cost is lowered
Phase-shift modulated Dual-Active Bridge Converter Operating Waveforms
Parameter ValueInput voltage 2.5 – 4.1 V
Output voltage 13 – 16 VPower rating 35 W
Peak efficiency 94 %Inductance, 𝐿𝐿𝑙𝑙 35 nH
Turns ratio, 𝑛𝑛𝑡𝑡 4Switching
frequency, 𝑓𝑓𝑠𝑠250 kHz
Hardware Results
• Life balancing extends battery life by reducing stress on weakest cells• Range no longer limited by weakest cell in the pack• Relaxes thermal management requirements
-- Passive Balancing
-- Life Balancing
Pack level results with life balancing control
Discharge Cycle (US06 drive cycles) Charge Cycle (15 A Constant Current)
• Cell-level and sub-string level DC/DC• Full pack implementation on PHEV • Long term validation tests in progress at NREL
with A/B passive versus Life Balancing
Team Partners
The information, data, or work presented herein was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000271.
Conclusion• Cost neutral integrated BMS-DC/DC system replaces existing BMS and
HV-to-LV DC/DC
• Life balancing leads to reduced capacity imbalance, increased lifetime, and
relaxed thermal management
• Range is no longer limited by weakest cell in the pack
• Proposed system architecture and life balancing is experimentally validated
PHEV20air-cooled
BEV75liquid-cooled
BEV225liquid-cooled
+29%
+42%
+45%
Battery Cell
bypass DC/DC
Battery Cell
shared bus
SELECT Annual Meeting and Technology Showcase – Logan, Utah – September 27-28, 2016
M. Muneeb Ur Rehman, Regan ZaneUtah State University
Fan Zhang, Dragan MaksimovićUniversity of Colorado Boulder
Kandler Smith, Ying ShiNational Renewable Energy Lab
Modular Approach for Active Cell-level Balancing toExtend Electric Vehicle Battery Pack Lifetime
• Dual-active bridge topology offers high efficiency and low rms currents• DC/DC is designed for nominal li-ion cell voltage and LV DC bus for
electric vehicles• DC/DC is designed with suitable power rating to enforce life balancing• DC/DC regulates output voltage and cell state-of-charge (SOC)
