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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