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# Regarding the impedance accuracy of ADBT1001

I am looking for a device that can measure the impedance of a lithium-ion battery in units of 10 mΩ. There is a statement that the ADBT1001 has a 16-bit ADC.

If the measured current is 20A, the reference 5V for this device
I thought it was possible with 5 ÷ 2 ^ 16Bit ÷ 20A ＝ 3.81μΩ.
Is it correct?

Parents
• Hi UBOTI,

There are two main ways that the ADBT1001 can be used to measure impedance.  Both involve performing a charge or discharge operation.  With DCIR, a constant current charge is setup and both battery voltage and current are measured.  A step in current is made and both voltage and current measured again.  Effectively, the internal resistance is difference in voltage divided by the difference in current.   The other method is ACIR where an AC signal is injected on top of the DC charge or discharge current.  This AC signal is synchronously demodulated on both voltage and current channels.  The demodulated voltage reading is divided by the demodulated current to get the battery impedance at the AC test signal frequency.

ACIR test measurements show < 200 uOhms in 100 Hz to 1kHz range for a short circuit.  With a 100 mOhm load, error can be less than 0.1%.

The ADBT1001 is a digital controller and uses a switching regulator for charge and discharge operations.  Other impedance measurement devices, such as the AD5941 use linear techniques for the AC measurements.

I hope this helps understand a bit on how the ADBT1001 can be used to measure impedance of a Li Ion cell.

Cheers,

George

• Hi UBOTI,

There are two main ways that the ADBT1001 can be used to measure impedance.  Both involve performing a charge or discharge operation.  With DCIR, a constant current charge is setup and both battery voltage and current are measured.  A step in current is made and both voltage and current measured again.  Effectively, the internal resistance is difference in voltage divided by the difference in current.   The other method is ACIR where an AC signal is injected on top of the DC charge or discharge current.  This AC signal is synchronously demodulated on both voltage and current channels.  The demodulated voltage reading is divided by the demodulated current to get the battery impedance at the AC test signal frequency.

ACIR test measurements show < 200 uOhms in 100 Hz to 1kHz range for a short circuit.  With a 100 mOhm load, error can be less than 0.1%.

The ADBT1001 is a digital controller and uses a switching regulator for charge and discharge operations.  Other impedance measurement devices, such as the AD5941 use linear techniques for the AC measurements.

I hope this helps understand a bit on how the ADBT1001 can be used to measure impedance of a Li Ion cell.