Testing of Lithium Ion Batteries Low-frequency AC-IR vs DC-IR
Method
Roy Hali Batenburg Mechatronica bv
Battery Production Process
Equivalent Circuit of the Electrode interface of a Battery
-Imaginairy (reactance) [Ω]
1kHz
0
10kHz
Real (resistance) [Ω]
Anode Cathode
Electrolyte
e-
e-
Electrolyte
+
+
+
+
+
+
+
+
+
Cathode
Electrode
Anode
ElectrodeBattery model
Equivalent Circuit of the Electrode interface of a Battery
0
Real (resistance) [Ω]
1kHz 1Hz
Anode Cathode
Electrolyte
e-
e- e-
e-
e-
e-
e-
e-
e-
ElectrolyteElectrode
+
++
+
+
e-+
e-
e-+
Charge transfer resistance
Electrical double layer capacitance
Battery model
Electrical double layer
-Imaginairy (reactance) [Ω]
Equivalent Circuit of a Battery
Cole Cole Plot and Equivalent Circuit
Basic Measurement Setup
DC-IR vs AC-IR (1)
DC-IR vs AC-IR (2)
Comparison of DC-IR and AC-IR methode of 24 Li-ion 18650-type cylindrical batteries with Trend Line
DC-IR vs AC-IR (3)
Considerations when using AC-IR Methode (1)
The Test Current
Considerations when using AC-IR Methode (2)
4-Terminal Method 4-Terminal Pair Method
Test Probe Wiring
Considerations when using AC-IR Methode (3)
Test Wiring Method
Considerations when using AC-IR Methode (4)
Measurement Probes
Current terminal
Voltage terminal
Traditional 4-Terminal clip
Currentterminal
Voltage terminal
4-Terminal Pair clip for use withlaminated batteries
Stopper
Considerations when using AC-IR Methode (5)
Measurement Probes
New
Traditional
BT4560 Battery Impedance Meter
Key features
• Low-frequency AC-IR measurement* : Measure the reaction resistance of a battery
*The BT4560 ensures battery cell quality by measuring internal impedance at a low frequency of 1 Hz or below
• Reliable measurements for low-impedance batteries because of 1.5A test current (< 1mΩ)
• Circuit configuration highly tolerant of contact and wire resistance to provide stable measurements
• Voltage measurement function equivalent to 6-digit DMM (± 0.0035% rdg.)
• Available in 5V, 10V and 20V version• Can be combined with switching devices for automated
testing
Software
Application 1: Selecting Li-ion Cells
Application 2: Check deterioration of Li-ion
Conclusions
• Low frequency AC-IR is a valid alternative for DC-IR measurement
• AC-IR reduces measurement time dramatically
• Possible to measure resistance of 1mΩ or less accurately
• 4-terminal pair test leads required to measure low resistance with AC-IR
• Select test probes that ensure repeatability
Q&A
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