TI E2E Community
Battery Management - Gas Gauge Forum
1) Why is the bq78PL114S12 still asking for charge (ChargingVoltage() and ChargingCurrent() are at the same value as not FullCharge)? This is quite different than the bq20z90.
2) Why, when at full charge and left with requested voltage applied, did the ChargingCurrent() change to the Pre-Charge value? (Happened once, didn't repeat)
3) Is there better information for normal operation (as with the bq20z90)?
I am not sure what you are asking in item 1) .
2) Did the Charge Complete flag get set? If so, the charge and precharge FETs should open and prevent any charging current. Are you sure that you are not seeing the taper current at the end of charge?
3) The information presented in the Technical Reference Manual is the best description that we have. Is there anything in particular that you have a question about?
The PL114 and bq20z90 are different implementations, so they operation will differ.
1) This is the first time in my battery development history (12 years, many Li+ bateries, many battery managers) that I've seen this interpretation of ChargingCurrent(). It doesn't seem to conform to the SBS spec 5.3.1 definition (notice the first item in note2). Previous experience always had ChargingCurrent() as a dynamic value, changing to zero when the battery reached full charge or wished to stop charging.
2) Only SBS information was being monitored. FC did set. Current() had tapered to ~10ma, so the Charge FETs were still conducting. Polling period was 4 seconds. ChargingCurrent() was 380 ma (=ChargingCurrent() value for PreCharge state) for at least 1 minute. Charging current reverted to normal value when charging supply was disconnected.
3) The Tech Reference Manual is mostly about about the abnormal operation, and didn't adequately describe normal charging operation, particularly the strong link to FET deactivation. Note: This mode of operation prohibits floating charge systems, and makes parallel battery operation uneccessarily complicated.
* While some differences are understandable, it is suprising that Texas Instruments, as a leader in battery management, would not have a singular interpretation of the standards and a more cohesive approach in their product line.
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