Other Parts Discussed in Thread: BQSTUDIO
I’m having trouble getting the BQ27542-Gq1 fuel gauge to enter hibernate mode. I can get the HIB bit set in the Control/Status register but the current consumption remains around 60uA which I believe indicates that the bit isn’t having the desired effect. I also have a bunch of questions about the part and BQ studio.
1) What is the accuracy of the voltage and current measurements (and ultimately the SoC) if the A2D isn’t calibrated?
2) When I select the 27542 in BQ Studio it says the part is unsupported and I’m using the tool at my own risk. What is this about?
3) How do I configure the part for the nominal value of my current sense resistor?
4) Does the part enter Hibernate mode once the HIB bit is set regardless of the charge or discharge current at the time?
5) When does the part exit Hibernate mode? The Ref manual (3.1.4) says the part will take a valid OCV measurement and then waits until the average current drops below Hibernate Current. But right after that it states that it will enter Hibernate mode if AverageCurrent > Hibernate Current OR the cell voltage < Hibernate_V. Does this mean that the part can enter Hibernate mode if the cell voltage is less than Hibernate Voltage even when the HIB bit is not set if the voltage is low?
6) Under what conditions does the part clear the Hibernate bit automatically. The rev manual states that the part will exit Hibernate mode when AverageCurrent > Hibernate Current and that the HIB bit is automatically cleared when the part “wakes up from Hibernate mode”. I have found that if I set the HIB bit with the EVM3400 and bqStudio, it remains set if I read registers inside the EVM3400 but gets cleared if I write to a parameter.
7) If I set the Hibernate bit then continue to charge or discharge the battery while periodically reading the SoC and/or battery voltage via the gauge will it enter Hibernate mode once the current to/from the battery drops below the threshold (Hibernate Current)?
8) It appears that a “Golden Image” created by bqStudio contains the device firmware in addition to the data flash contents. Assuming that the firmware in the part matches what I want, is it acceptable to program just the data flash?
9) After setting up the DF registers to match the battery I’m using (60 mAh, one cell) and writing those values to the device I find that many of the register values don’t make sense. For instance the “Nominal Available Capacity” shows 846mAh and several other mAh values are much higher than the 60mAh battery capacity. Why is this and what should I do about it?
10) What other things (eval modules, chargers, software, etc.) do I need if I want to properly configure the gauge for the battery I’m using? Do I really need to run charge discharge cycles for thousands of hours? What is the effect on the SoC accuracy if I don’t do this?
11) What is a “GPG Cycle”?
