1. Methodology for supercapacitor performance measurements
Dr. Natalia Stryzhakova
Dr. Yurii Maletin
Dr. Sergiy Zelinskiy

2. Methodology for supercapacitor performance measurement
References
FreedomCAR Ultracapacitor Test Manual. Idaho National Laboratory Report DOE/NE-ID-11173, September 21, 2004.
IEC Fixed electric double layer capacitors for use in electronic equipment. Part 2. Sectional specification – Electric double layer capacitors for power application.
IEC Electric double layer capacitors for use in hybrid electric vehicles – Test methods for electrical characteristics.
A. Burke, M. Miller. Testing of Electrochemical Capacitors: Capacitance, Resistance, Energy Density, and Power Capability. ISEE’Cap09 Conference, Nantes,
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.
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
A. Burke. Testing Large Format Electrochemical Capacitors. Tutorial of ISEECap2011, Poznan, Poland, June 12, 2011.

3. Main characteristics of a supercapacitor unit cell
Methodology for supercapacitor performance measurement
Main characteristics of a supercapacitor unit cell
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 (-40…+70 ºC)
Cycle life
Self discharge
Calendar life (hours) at rated voltage and high temperature (60 ºC)

4. Test procedures Constant current charge/discharge
Methodology for supercapacitor performance measurement
Test procedures
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 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)

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

6. Capacitance Test procedure: Constant current charge/discharge
Methodology for supercapacitor performance measurement
Capacitance
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%.

7. Capacitance Test procedure: Constant current charge/discharge
Methodology for supercapacitor performance measurement
Capacitance
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

8. Capacitance Test procedure: Constant current charge/discharge
Methodology for supercapacitor performance measurement
Capacitance
Test procedure: Constant current charge/discharge
Yunasko procedure
1) A set of current values from 0.2Itest to Itest.; Itest 200 A
2) From С = f(I) plot the С0 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.

9. Yunasko supercapacitor cell:
Methodology for supercapacitor performance measurement
Capacitance
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
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 9

10. Methodology for supercapacitor performance measurement
Internal resistance
Equivalent Series Resistance (ESR) - the resistance due to all the resistive components within the supercapacitor.
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. 10

11. Internal resistance Test procedure: Constant current method,
Methodology for supercapacitor performance measurement
Internal resistance
Test procedure: Constant current method,
sampling rate of 10 ms 11

12. Internal resistance ESR is independent of current value.
Methodology for supercapacitor performance measurement
Internal resistance
ESR is independent of current value.
EDR value depends on testing current 12

13. Methodology for supercapacitor performance measurement
Internal resistance
Measurements using the voltage recovery after current interruption
(Maxwell procedure) 13

14. Internal resistance Yunasko procedure
Methodology for supercapacitor performance measurement
Internal resistance
Yunasko procedure 14

15. Internal resistance Pulse procedure (Arbin)
Methodology for supercapacitor performance measurement
Internal resistance
Pulse procedure (Arbin)
Rpulse = Average (Voltage at P2 – Voltage at P3) / (2 I). 15

16. Internal resistance Comparison of different procedures: Conclusions:
Methodology for supercapacitor performance measurement
Internal resistance
Comparison of different procedures:
 Yunasko
cells
C, F
Resistance, mOhm
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. 16

17. Specific energy and power
Methodology for supercapacitor performance measurement
Specific energy and power
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 = U×I×Δt during charge and discharge.
The usable specific energy Em (Wh/kg)
The efficiency η:
Ragone plot: a plot illustrating Em (or Ev) vs Pm (or Pv)

18. Specific energy and power
Methodology for supercapacitor performance measurement
Specific energy and power
Test procedure: Constant power tests, Ragone plot

19. Specific energy and power
Methodology for supercapacitor performance measurement
Specific energy and power
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

20. Specific energy and power
Methodology for supercapacitor performance measurement
Specific energy and power
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 :
where
U6=0.2U (20%)
Ue=0.4U (40%)
The power at efficiency η and at discharge from the rated voltage Ur to Ur/2:
NOTE: YUNASKO normally uses the η value of 0.95

21. Methodology for supercapacitor performance measurement
Self-discharge test
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 (%)

22. Self-discharge test - example
Methodology for supercapacitor performance measurement
Self-discharge test - example
where B is the voltage maintenance rate (%)

23. Methodology for supercapacitor performance measurement
Cycle-life test
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 ± 3°C.
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)

24. Cycle-life test – SC example
Methodology for supercapacitor performance measurement
Cycle-life test – SC example
Cycling a 1200F device between 2.0 and 3.2 V at 60 °C

25. Cycle-life test – hybrid capacitor example
Methodology for supercapacitor performance measurement
Cycle-life test – hybrid capacitor example

26. Temperature Performance
Methodology for supercapacitor performance measurement
Temperature Performance
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 25±3°C 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 ± 3°C until thermal equilibrium is achieved. Perform the above mentioned tests at this temperature.
Step 3 - Condition the capacitor at -30 ± 3°C until thermal equilibrium is achieved. Perform the above mentioned tests at this temperature .
Step 4 - Condition the capacitor at 25 ± 3°C 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

27. Temperature performance
Methodology for supercapacitor performance measurement
Temperature performance
Hybrid
EDLC

28. Methodology for supercapacitor performance measurement
Endurance test
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 ± 3°C 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 ± 3°C.
1. Constant-Current Charge/Discharge (In)
2. ESR (from constant-current test data)
3. Constant Power Discharge (200 W/kg, 1000 W/kg)

29. Methodology for supercapacitor performance measurement
Endurance test

30. Methodology for supercapacitor performance measurement
Conclusions
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)

31. Methodology for supercapacitor performance measurement
Acknowledgements
Special thanks to my R&D 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 (Energy Caps) is very much acknowledged

32. THANKS FOR YOUR ATTENTION! Please visit us at: www.yunasko.com