Other Parts Discussed in Thread: EV2400, BQSTUDIO, BQ25700AEVM-732
Hello,
I am having issues completing the learning cycle on my BQ40z50 EVM board when following the instructions outlined in this document:
Specifically, I think my problem is that the [Qmax] measurement is not being made during the post charge rest period as the [VOK] bit is never being cleared and the “No Of Qmax Updates” field in the data memory never updates.
Test System: A BQ40z50EVM is connected to a Windows 10 PC running bqStudio via an EV2400. For charging the battery, a BQ2577aEVM is connected to the same PC via another EV2400. The battery is a commercially available Samsung1.5 Ah NMC power cell bought online.
To start the learning cycle, I first re-flashed the firmware on the BQ40z50 and set the following values for our battery in the data memory section of bqStudio:
Chem ID: 0x0259
Design Capacity: 1500 mAh
Charge Term Taper Current: 70 mA
Discharge current threshold: 45 mA
Charge current threshold: 40 mA
Quit Current Threshold: 10 mA
Term Voltage: 2500 mV
I then completed calibrations of current and voltage readings with bqStudio.
- Initial discharge: The learning cycle was started by sending the “unseal” command followed by the FET enable (FET_EN) and gauge enable (GUAGE_EN) commands, followed by observing the registers VOK, QEN and REST, followed by a RESET command. I then started to discharge the battery down to 2500 mV at a rate of C/3, and then let it rest. I believe this rest was successful as eventually the VOK and RDIS bits cleared, and the REST flag went high, as described in the learning cycle document.
- Full Charge: After the initial discharge and rest, I started the charge phase by sending the Gauge_Enable command and setting the charge rate to ~C/2. The charger tapered current as we reached full charge (4200 mV) on the battery. I turned off the charger once the battery voltage reached 4200 mV. At this time, the charge current was ~100 mA. I then began the post charge rest period. This is when the observed values of registers started to deviate from what we expected. Even after a 7 hour rest period, the VOK bit was not clearing. Even after waiting for 20 hours, the VOK bit did not clear and update status never went to 0x05.
- Full slow-discharge: After waiting 20 hours, we just started a C/5 discharge anyways, since it was Sunday and no other work was planned. After the C/5 discharge, there was a >5 hour rest, but update status did no change to 0X0E, not that we expected it to as we did not think things updated correctly after the charge rest period.
Please let me know if you have any specific questions of suggestions. Since the log file is too big to include as an attachment, it can be found as a link on my Google drive here:
Thank you,
