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Active Measurement Cancellation

Isolating batteries from active circuits to measure cell impedance in-line

Idaho National Laboratory

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Publications:

PDF Document PublicationTechnology Fact Sheet (937 KB)

Active Measurement Cancellation uses two measurement points in a battery string and eliminates the need for post-measurement calculations.
Active Measurement Cancellation uses two measurement points in a battery string and eliminates the need for post-measurement calculations.

Technology Marketing Summary

Impedance measurements are used to assess the state and health of many systems, including structural crack measurements, stress indicators, and batteries. Electrochemical batteries lose capacity over their service lifetime,typically because battery use causes chemical degradation with increasing resistance until it can no longer supply a useful amount of power. Impedance measurements are currently performed by placing a shunt in series with the battery to determine battery current. The resulting battery current and voltage are used to calculate battery impedance.  This system works well for isolated batteries, but does not work for modules with many interconnected batteries and no provision for placing a shunt within the module.  Using a different method, a measurement system injects a signal across a single battery, the signal response is a composite of the entire battery module and everything connected to the module.  The individual battery impedance is distorted by all other connections to the battery.  This same problem exists when attempting to measure element impedance within any type of active circuit. 

Description

Researchers at INL have developed a method known as Active Measurement Cancellation (AMC) for measuring impedance.  This new method is effective for measurement of isolated components as well as active, interconnected circuits, allowing impedance measurement in situ. The AMC circuit is capable of cancelling the effects of the interconnected circuit, measuring only the response of the desired component, eg. a battery cell, thereby allowing accurate, immediate, impedance measurements of the components even when in use.

Benefits
  • Ability to accurately measure real-time impedance of a component even in an energized system
  • The ability to measure impedance of a component, in situ, without modifying the circuit
  • Uninterrupted and unimpaired operation of battery module.
  • Greater insight into polarization effects
Applications and Industries
  • Electric vehicle systems
  • Portable electronics, such as phones, laptops, and wearables
  • Energy storage systems
More Information

This technology has been tested and validated at the bench scale. Additional development will be required to integrate this technology into a commercially viable product. BEA may be in a position to support additional research and development of this technology under a mutually acceptable Cooperative Research & Development Agreement (CRADA), Strategic Partnership Projects (SPP), or similar agreement subject to prior approval by DOE.

Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Date
Patent 9,519,031
Patent
9,519,031
Circuits and methods for impedance determination using active measurement cancelation
A delta signal and opposite delta signal are generated such that a sum of the two signals is substantially zero. The delta signal is applied across a first set of electrochemical cells. The opposite delta signal is applied across a second set of electrochemical cells series connected to the first set. A first held voltage is established as the voltage across the first set. A second held voltage is established as the voltage across the second set. A first delta signal is added to the first held voltage and applied to the first set. A second delta signal is added to the second held voltage and applied to the second set. The current responses due to the added delta voltages travel only into the set associated with its delta voltage. The delta voltages and the current responses are used to calculate the impedances of their associated cells.
Idaho National Laboratory 12/13/2016
Issued
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
BA-671PrototypeAvailable09/11/201709/08/2017

Contact INL About This Technology

To: Ryan Bills<ryan.bills@inl.gov>