CN0510

Hi,

Kindly refer to 

- (+) Software operation of battery impedance spectrum measurement - Q&A - Reference Designs - EngineerZone (analog.com) 

(+) AD5941BATZ：Sensor pal's Nyquist graph derived data, the imaginary part of the impedance is positive - Q&A - Reference Designs - EngineerZone (analog.com)

Could  you  give  me  more details?   How to set the resistance of calibration resistor? If the internal resistance of my current battery is only 10mohm, can I measure it with CN0510? Is it necessary to ensure that the calibration resistance is less than the internal resistance of the battery? How to determine the amplitude of alternating current applied to different batteries and how to choose the bias voltage? Is EIS only measured by high-frequency excitation circuit, and low-frequency excitation circuit is used to measure battery impedance at specified frequency, right? Is there a corresponding routine for measuring the battery impedance at the specified frequency? If so, can you provide it? Only by adjusting the software, can we accurately obtain the battery internal resistance of 0.01hz? Thanks for the answer.

 Hi,

How to set the resistance of calibration resistor?

Calibration resistor value is preferred to be close to expected Battery impedance value.

If the internal resistance of my current battery is only 10mohm, can I measure it with CN0510?

Yes.

Is it necessary to ensure that the calibration resistance is less than the internal resistance of the battery?

Not necessary.

How to determine the amplitude of alternating current applied to different batteries and how to choose the bias voltage?

The voltage generated at CE0 is used to turn ON the Darlington pair (highlighted in the diagram). Current though the battery is generated by the battery's supply voltage.

CE0 output voltage range = ±607 mV

Bias voltage is usually fixed to 1.1V to allow maximum +ve and -ve voltage swing at CE0.

Is EIS only measured by high-frequency excitation circuit, and low-frequency excitation circuit is used to measure battery impedance at specified frequency, right?

EIS and Battery measurement can be done for entire range of excitation frequencies (0.15Hz till 200KHz).

Is there a corresponding routine for measuring the battery impedance at the specified frequency? If so, can you provide it?

The example code in Github (ad5940-examples/examples/AD5940_BATImpedance at master · analogdevicesinc/ad5940-examples · GitHub) could be run using Keil or IAR IDE.

For measuring at a particular frequency, set in AD5940Main.c:

pBATCfg->SinFreq = 200;    //your desired frequency

pBATCfg->SweepCfg.SweepEn = bFALSE;  //Disable frequency sweep disable

Only by adjusting the software, can we accurately obtain the battery internal resistance of 0.01hz?

Accuracy at 0.01Hz is not achieved/ guaranteed till now.

Hi,

Apologies for ambiguity.

AC amplitude voltage range at CE0 = +/-607mV.

Output at CE0 = Bias voltage + AC voltage

0.2V<=Bias voltage allowed <=2.4V

-607mV<=AC voltage  allowed<=+607mV

0.2V<=Total voltage output at CE0 allowed<=2.4V

Any voltage beyond this range gets clipped.

Yes. Correct.

AIN1 gets the +ve feedback from load, which is used for controlling excitation at CE0, as shown in the diagram.

The picture:

Yes. As long as the output CE0 voltage is a standard sine wave, the device is operating normally.

Hi,
I have some questions to make sure that this equipment is fit for my case.
I want to make EIS measurements on high-capacity (70 to 160Ah) lithium ion batteries.
First I want to measure them at nominal voltage. Then the battery will be overdischarged to 0V, after which the battery voltage should rebound to a level somewhere between 0 and 2,5V.

So now I have a few questions:
For the test at nominal voltage, have you done any tests with high capacity batteries with this equipment, or do you know of any? I am wondering if the excitation current will be enough, because of the lower c-rate and current density.

Then for the overdischarged batteries, will it be possible to do an impedance measurement with this equipment for a battery that is let's say at 0,5V?

I am slightly confused about the calibration resistor. As far a I understand the calibration resistor physically on this board is 50mOhm. But I read in the AD5941 datasheet that an external calibration resistor can be connected.
Is this necessary in my case? (I expect around 1-5mOhm)

What calibration resistance value do you input into the program? Always the expected value of the battery impedance, or the value of the connected calibration resistor (which would then be 50mOhm if no external resistor is connected)?

From what I have read in the datasheets and in this forum, the lowest frequency with accurate results is 0,15Hz. Is this low enough to estimate the warburg impedance and visualise the 45degree line in the nyquist plot?

Thanks in advance,
Lucas