BQ27520-G4: Max Res Factor and Min Res Factor

Hi Yaita,
Sorry for the late response, it is not recommended to adjust these factors arbitrarily, for instance, default value of Max Res Factor allows the change in positive direction of the filtered Ra grip-point to 1.5x times the old Ra value. If change in filtered Ra value exceeded Max Res Factor then [RUP_DIS] bit in Control_Status() will be set to stop Ra values update until a good relaxed OCV measurement is taken. The loose value that Max Res Factor can take is 2x. and the large degradation ratio of battery impedance suggests an aged battery.

Regards,
Haidar

Hi Yaita-san,

Setting it more than 2x means allowing impedance values stored in Ra table to change more than 2 times its old values which results in fluctuation in Ra values as it updates. Battery impedance profile (hockey stick) will be affected if such fluctuation happens in Ra values and that's why default values for Ra Filter, Ra Max Delta, Max Res Factor, and Min Res Factor were chosen to martian such impedance profile as battery impedance change(increase) while battery ages.

Regards,

Haidar  

Hi Yaita San,

My apology for misspelling maintain "I wrote martian"  in my previous post, as for the hockey stick, I was referring to the battery impedance profile vs depth of charge as you can see in screen shot below which looks like a hockey stick, this photo is from figure 6 in the attached document.

.  

What I meant to say if we let battery Ra table values to change loosely, there will be fluctuation and distortion in battery impedance profile thus affecting gauging algorithm and gauging accuracy in return. That's why there are many limitation, filtering and checking for battery impedance,Ra values, change to maintain such impedance profile.

Regards,

Haidar