We are trying to force a permanent fault condition during balancing to check the pack behaviour.
The setup is as shown below
BMS setup information:
BQ40z50-R2 balance behaviour:
I added this section to get some feedback on my understanding of the BQ ic behaviour.
According to Section 7.2 Cell Balancing Setup, the unit needs to enter relax mode before it can determine if cells are unbalanced and how much balancing is required.
In order to enter relaxed state, the current needs to be lower than the quit current, then an internal timer is set and must exceed “CHG Relax Time” or “DSG Relax Time”.
Once in relax mode and OCV is acquired the BQ ic calculates the balance time as shown below.
Experiment:
During our testing we unbalanced cell 4 to a point where we hit the maximum 65535s limit.
We have hit the limit of 65535s for cell 4 cell balancing time as shown below.
However, from section 3.9 of the technical reference for the BQ ic it states the following.
Which we believe are these values.
If this is the case, then the permanent failure will never occur?
Which brings me to my question.
Are we understanding this correctly ?
Do we need to alter the Max Threshold and Delta Threshold values?
Any assistance would be greatly appreciated.
