TI E2E Community
Battery Management - Gas Gauge Forum
EVSW for bq27425EVM
I'm evaluating the bq27425 that I've just received. The first thing I noticed after opening the evaluation software is that the calibration tab is nowhere to be seen! How am I supposed to calibrate my pack current, which is offset by 13mA at 1A!
With no current applied does your gauge read 0mA? You'll notice that the EVSW has no bqEASY tab or Calibration tab. We will be releasing a standalone tool shortly called bqConfig that will guide you through the configuration and calibration of the bq27425. The calibration section will only allow you to calibrate voltage offset and board current offset. You will not be able to calibrate current gain because...
This gauge doesn't require current calibration by the user. Current measurement is calibrated at the factory to the level required for correct operation of the fuel gauging algorithm.
Yes, with no current applied the EVSW reports 0mA. It is at C-rate level currents (1.5A for my 1500mAh battery) that the values differ by more than 10mA. How long might I have to wait for that standalone tool?
Why is it that the the Dsg Current Threshold, Chg Current Threshold, and Quit Current defaults are 167mA, 133mA, and 250mA (respectively)? The Quit Current has always been illustrated to be smaller in magnitude than both the Chg and Dsg Current Thresholds, so why the change now? I had changed them to 90, 113, and 60mA, according to the formulas in SLUSAI6, however they appear to have been reset to the default values. How can I change these values (again) without the gauge losing any information learned thus far? I believe I used 0x0013 (SET_CFGUPDATE) and 0x0042(SOFT_REST) before.
What is the purpose of using "0.1h" as a unit of measurement for these thresholds when mA would suffice and actually be understood?
Is there a document, similar to SLUA450, which explains the algorithm for the bq27425? I would like to know (among other things) what the wait times are for entering the different modes of operation. The Chg Relax Time Period appears to be very long (greater than 30min). I was charging at 1.5A (C-rate) and stopped at SoC 65% where it has been 'resting' for 50min. CHG is red, DSG is green, VOK is red, OCVTAKEN is green. I expect DSG to go red when relaxation mode is entered, which hasn't happened yet. The change in voltage over time achieved less than 4uV/s after ~20min.
1537.May 15 2012 special export.txt
OCVTAKEN just turned red after almost an hour.
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