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Methodology for supercapacitor performance
measurements

Dr. Natalia Stryzhakova Dr. Yurii Maletin Dr.
Sergiy Zelinskiy
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References
Methodology for supercapacitor performance
measurement

1. FreedomCAR Ultracapacitor Test Manual. Idaho
   National Laboratory Report DOE/NE-ID-11173,
   September 21, 2004.
2. IEC 62391-2 . Fixed electric double layer
   capacitors for use in electronic equipment. Part
   2. Sectional specification Electric double
   layer capacitors for power application.
3. IEC 62576. Electric double layer capacitors for
   use in hybrid electric vehicles Test methods
   for electrical characteristics.
4. A. Burke, M. Miller. Testing of Electrochemical
   Capacitors Capacitance, Resistance, Energy
   Density, and Power Capability. ISEECap09
   Conference, Nantes, 2009.
5. A. Burke, M. Miller. Testing of Electrochemical
   Capacitors Capacitance, Resistance, Energy
   Density, and Power Capability. Idaho National
   Engineering Laboratory Report DOE/ID-10491,
   October 1994.
6. S. Zhao, F. Wu, L. Yang, L. Gao, A. Burke. A
   measurement method for determination of dc
   internal resistance of batteries and
   supercapacitors. Electrochemistry Communications,
   2010, v.12, p.242-245.
7. A. Burke. Testing Large Format Electrochemical
   Capacitors. Tutorial of ISEECap2011, Poznan,
   Poland, June 12, 2011.

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Main characteristics of a supercapacitor unit
cell
Methodology for supercapacitor performance
measurement

• Rated voltage, Ur (V)
• Capacitance, C (F)
• Internal resistance, R (Ohm)
• Specific energy, E (Wh/kg)
• Specific power, P (W/kg)
• Specific energy vs. Specific power (Ragone plot)
• Resistance and capacitance vs. temperature
  (-4070 ºC)
• Cycle life
• Self discharge
• Calendar life (hours) at rated voltage and high
  temperature (60 ºC)

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Test procedures
Methodology for supercapacitor performance
measurement

• Constant current charge/discharge
• Capacitance and resistance
• Cycle life
• Pulse tests to determine resistance
• Constant power charge/discharge
• Ragone Plot for power densities between 100 and
  at least 1000 W/kg for the voltage between Ur
  and ½ Ur.
• Test at increasing W/kg until discharge time is
  less than 5 sec. The charging is often done at
  constant current with a charge time of at least
  30 sec.
• Voltage maintenance
• Self discharge test
• Continuous application of rated voltage at high
  temperature
• Endurance test (calendar life estimation)

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Capacitance
Methodology for supercapacitor performance
measurement
Test procedure Constant current
charge/discharge USABC test procedure
Normal Test Currents (Discharge Charge) Test Currents Test Equipment Limited to ITEST lt IMAX (Discharge Charge)
Minimum Test Current 5C 5C
Other Test Currents 0.1 IMAX 0.1 ITEST
Other Test Currents 0.25 IMAX 0.25 ITEST
Other Test Currents 0.5 IMAX 0.5 ITEST
Other Test Currents 0.75 IMAX 0.75 ITEST
Maximum Test Current IMAX ITEST

• Current of 5C corresponds to 12 min discharge
• IMAX can be chosen as the lowest of (a) the
  current required to cause an immediate ( lt0.1 s)
  20 voltage drop in a fully charged device at 30
  ºC, or (b) the current required to discharge the
  device from UMAX to UMIN within 2 s.
• At least 5 cycles at each current value

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Capacitance
Methodology for supercapacitor performance
measurement
Test procedure Constant current
charge/discharge IEC procedure ( 62576)
Single test to determine the capacitor
performance at a single current so that the
efficiency in charge and discharge to be of 95.
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Capacitance
Methodology for supercapacitor performance
measurement
Test procedure Constant current
charge/discharge UC Davis procedure (ITS,
Dr.A.Burke)
1) The nominal charge/discharge current In
corresponding to nominal power density (200 or
400 W/kg)
2) A set of current values 0.25, 0.5, 1.0, 2.0,
4.0, 8.0In
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Capacitance
Methodology for supercapacitor performance
measurement
Test procedure Constant current
charge/discharge Yunasko procedure
1) A set of current values from 0.2Itest to
Itest. Itest 200 A
2) From ? f(I) plot the ?0 max capacitance
value (extrapolation to zero current) and -dC/dI
value (the slope) can be found. NOTE The -dC/dI
slope characterizes the system behavior at high
power loads and depends on electrode material and
system design.
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Capacitance
Methodology for supercapacitor performance
measurement

• Conclusions
• Capacitance value depends on test conditions,
  though, not dramatically.
• Testing current conditions differ significantly

Yunasko supercapacitor cell 1200F, 0.15 mOhm, 0.12 kg Yunasko supercapacitor cell 1200F, 0.15 mOhm, 0.12 kg
Procedure Itest, range, A
USABC from 2.5 A (5C) to 800 A (Imax)
IEC 450 A
ITS from 35 A to 280 A
Yunasko from 40 A to 200 A
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Internal resistance
Methodology for supercapacitor performance
measurement

1. Equivalent Series Resistance (ESR) - the
   resistance due to all the resistive components
   within the supercapacitor.
2. Equivalent Distributed Resistance (EDR) includes
   ESR and an additional contribution from the
   charge redistribution process in the electrode
   pore matrix due to non-homogeneous electrode
   structure, the process adding significantly to
   Joule heating I2Rt.

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Internal resistance
Methodology for supercapacitor performance
measurement
Test procedure Constant current method,
sampling rate of 10 ms
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Internal resistance
Methodology for supercapacitor performance
measurement
ESR is independent of current value. EDR value
depends on testing current
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Internal resistance
Methodology for supercapacitor performance
measurement
Measurements using the voltage recovery after
current interruption (Maxwell procedure)
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Internal resistance
Methodology for supercapacitor performance
measurement
Yunasko procedure
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Internal resistance
Methodology for supercapacitor performance
measurement
Pulse procedure (Arbin)
Rpulse Average (Voltage at P2 Voltage at P3)
/ (2 I).
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Internal resistance
Methodology for supercapacitor performance
measurement
Comparison of different procedures
 Yunasko cells C, F Resistance, mOhm Resistance, mOhm Resistance, mOhm
 Yunasko cells C, F pulse ESR interruption
E-type 1500 0.242 0.225 0.265
P-type 1200 0.091 0.101 0.104
Conclusions Internal resistance measurements
involve different time intervals to fix the
voltage drop/jump. Resistance values depend on
test conditions, in particular, on time interval
and testing current chosen.
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Specific energy and power
Methodology for supercapacitor performance
measurement
Test procedure Constant power tests
1) Power values between 200 and at least 1000 W/kg
2) For each constant power test, the energy is
calculated as E UI?t during charge and
discharge. The usable specific energy Em (Wh/kg)
The efficiency ?
Ragone plot a plot illustrating Em (or Ev) vs Pm
(or Pv)
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Specific energy and power
Methodology for supercapacitor performance
measurement
Test procedure Constant power tests, Ragone plot

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Specific energy and power
Methodology for supercapacitor performance
measurement
Maximum energy stored - the energy that can be
obtained at discharge from the rated voltage to
zero
Available energy - at discharge from the rated
voltage Ur to Ur/2
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Specific energy and power
Methodology for supercapacitor performance
measurement
Maximum power (matched impedance power) - the
power that can be delivered to the load of the
same resistance as a supercapacitor.
Power density according to IEC 62391-2
where U60.2U (20) Ue0.4U (40)
The power at efficiency ? and at discharge from
the rated voltage Ur to Ur/2
NOTE YUNASKO normally uses the ? value of 0.95
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Self-discharge test
Methodology for supercapacitor performance
measurement
The time dependence of the capacitor
self-dissipation, i.e., the rate of internal
processes that cause the capacitor discharge when
not connected to a load.
where B is the voltage maintenance rate ()
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Self-discharge test - example
Methodology for supercapacitor performance
measurement
where B is the voltage maintenance rate ()
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Cycle-life test
Methodology for supercapacitor performance
measurement

• Stable performance over more than 100,000
  charge/discharge cycles is desired.
  Constant-current charge and discharge are used.
• Typical procedure
• Condition the capacitor at 25 3C.
• Charge the device by a current I chosen so that
  the voltage reaches Ur in 30 s.
• Maintain voltage Ur of the device for 15 s.
• Then discharge the capacitor to Umin with
  current I.
• Hold the capacitor at Umin for 50 s.
• Repeat cycling.
• Devices shall be characterized initially and
  after 1000 4000 10,000 40,000 100,000
  cycles.
• Characterization tests to be performed at each
  measurement cycle include
• 1. Constant-Current Charge/Discharge (In)
• 2. ESR (from constant-current test data)
• 3. Constant Power Discharge (200 W/kg, 1000 W/kg)
  

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Cycle-life test SC example
Methodology for supercapacitor performance
measurement
Cycling a 1200F device between 2.0 and 3.2 V at
60 C
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Cycle-life test hybrid capacitor example
Methodology for supercapacitor performance
measurement
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Temperature Performance
Methodology for supercapacitor performance
measurement
Temperature influences the energy that can be
stored in a device as well as the power it can
deliver. Typical procedure Step 1 - Condition
the device at 253C and perform the followed
tests 1. Constant-Current Charge/Discharge (In)
2. ESR (from constant-current test data) 3.
Constant Power Discharge (200 W/kg, 1000 W/kg) .
Step 2 - Condition the capacitor at 60 3C
until thermal equilibrium is achieved. Perform
the above mentioned tests at this
temperature. Step 3 - Condition the capacitor at
-30 3C until thermal equilibrium is achieved.
Perform the above mentioned tests at this
temperature . Step 4 - Condition the capacitor at
25 3C and repeat the tests listed above. This
test data will provide information about the
stability of the capacitor under thermal cycling
conditions. Step 5 - Perform a visual inspection
of the capacitors to identify any damage or
electrolyte leakage caused by the thermal cycle
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Temperature performance
Methodology for supercapacitor performance
measurement
Hybrid
EDLC
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Endurance test
Methodology for supercapacitor performance
measurement

• This procedure characterizes device life
  properties and performance using an accelerated
  aging condition.
• Typical procedure
• Device properties and performance are measured
  initially and then periodically throughout the
  aging period.
• Age the capacitors in a suitable oven or
  environmental chamber maintained at 60 3C with
  an applied voltage equal to Ur.
• Characterization tests of the devices should be
  performed at the start of the test sequence and
  after 250 10, 500 25, 1000 50, and 2000
  100 hours. Measurements are made at 25 3C.
• 1. Constant-Current Charge/Discharge (In)
• 2. ESR (from constant-current test data)
• 3. Constant Power Discharge (200 W/kg, 1000 W/kg)

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Endurance test
Methodology for supercapacitor performance
measurement
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Conclusions
Methodology for supercapacitor performance
measurement

• There is a need to further standardization of
  test procedures.
• The largest uncertainty is related with the
  resistance measurements.
• The effective capacitance of carbon/carbon
  devices is well-defined from constant current
  tests, but varies with the voltage range used it
  is recommended the voltage range of Vr and Vr/2
  to be used.
• Further work is needed to define the effective
  capacitance and resistance of hybrid capacitors.
• The energy density should be measured at the
  constant power discharge this is especially the
  case for hybrid capacitors
• Definition and determination of maximum power
  capability of both supercapacitors and lithium
  batteries remains a very confused issue (A.F.
  Burke)

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Methodology for supercapacitor performance
measurement
Acknowledgements
Special thanks to my RD and Design Bureau
colleagues S.Podmogilny, S.Chernukhin,
S.Tychina, D. Gromadsky, O.Gozhenko, A.Maletin,
D.Drobny, and A.Slezin Our Pilot Plant and
Administrative Department For the great
support, diligence and dedication to work YUNASKO
investment, technical, scientific and industrial
partners For the great collaboration and
support during the projects Many thanks to Dr.
Andrew F. Burke (ITS) and Dr. John R. Miller
(JME) for their measurements and
stimulating discussions Financial support from
FP7 Project no. 286210 (Energy Caps) is very much
acknowledged

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