BQ34Z100 : registers configuration

Hi John,

Have you found a chemID match for your cells? Your battery chemistry might be different from the default settings. Here are instructions for performing a chemID match if you need them:http://www.ti.com/tool/GPCCHEM.

You will also want to set the charge termination voltage and cell termination voltage according to your battery datasheet.

Best Regards,
Ben Lough

Hi Benjamin,

Thank you for your answer.

For the moment, I didn't change the chemID, thinking that it would not have a huge impact on the wrong values like voltage (I am totally new in battery gauging so I didn't know it was so important). I thought the values would be closer to the truth even without the chemID so I didn't search a lot for that. I will search for a better chemID.

Hovewer, I saw in the datasheet that "Device Chemistry" is a string. But chemID is a number. Where should I use the chemID?

I saw in another thread that BQStudio is necessary to change the chemID. Is that true? Isn't it possible to do that only with a microcontroller? 

Best Regards

John,

1) I would recommend performing calibration (board offset, current, voltage) if you are not seeing correct voltage values. Perform each of these separately.

2) If you follow the instructions for the chemID match tool I linked in my previous post, it will determine the best chemID match based on your charge/discharge profile. For the bq34z100, there is a Chemistry tab in bqstudio where you can select your chemID and it will program all necessary values for you.

3) You will want to use bqstudio to program your chemID at least for the first time. Once you have configured the bq34z100 correctly and are satisfied with the performance you are getting, you can export a .dffs file which contains all write instructions needed to configure another gauge.

Best Regards,
Ben Lough

Hi,

The problem is that I can't afford to buy the EV2300. My firm would like to use the BQ34Z100-g1 and I have to test it before they do that. But I will not be the one who will use the BQ34Z100. Somebody else, somewhere else, will do that. So, I can't buy the EV2300 only for one test.

I can communicate thanks to a microcontroller with I2C. Isn't it possible to change all the parameters alone with the microcontroller? Don't you have a document with all registers that need to be change with their values (depending the chemical ID)?

For voltage and current calibration, is bqStudio software also necessary? Or is it possible to do that with a microcontroller?

Best Regards

Hi John,

Are you able to collect Voltage, Current and Temperature data for the chemID tool? Once you identify the chemID for your battery, I can provide write instructions to program the gauge.

It is easier to calibrate using bqstudio but it is possible with a microcontroller. You will need to adjust [Voltage Divider] for voltage calibration and [CC Gain],[CC Delta], [CC Offset] for current calibration. Section 6.1 of the data flash guide might be useful to you: www.ti.com/.../slua664.pdf.

The bq34z100 also has an autocalibration feature you might be able to take advantage of (bottom of page 26: www.ti.com/.../bq34z100.pdf).

Best Regards,
Ben Lough

Hi,

I will probably not have the time to collect datas for the chemical ID. I am running out of time because my internship finishes in a few days. But if I have time, I will do it.

I did the voltage and current calibration. Current values are now correct (Current, averageCurrent...).

The voltage value is closer to the applied voltage but there is still at least 1V of difference. Maybe it comes from my voltage divider value. If I am using the BQ34Z100EVM, should I enter the value given by the formula in the BQ34Z100-G1 datasheet (voltageDivider = 300kOhm*900mV/15.5kOhm+900mV = 17264mV) or the maximum voltage of my battery (12600mV)?

The other commands give me wrong values. RemainingCapacity, stateOfCharge... are too small. And I still have MaxError = 100%. Do you think that the chemical ID could fix these values. My battery is a lithium-ion battery (ansmann 18650 3s1p). Is there so many differences between the default chemical ID and other lithium-ion chemical ID?

Best Regards

John,

Remaining capacity, state of charge, full charge capacity, etc. will not be accurate until you match a chemID for your battery and perform a learning cycle. The chemID includes voltage and internal resistance information for various states of discharge which can vary quite a bit from battery to battery.

Best Regards,

Ben Lough