Other Parts Discussed in Thread: BQSTUDIO, BQ34Z110
Good morning, I have a question related to the learning cycle of my fuel gauge. I am using PbA 12V, 7Ah battery. Moreover, I am using the bq34z100G1. I made some configurations since the BqStudio and using the EVM2300. One of the most important configurations are the following ones:
Taper Current = 100mA (default)
FC SET% = -1
CC Threshold = 6300 mAh
Design Capacity = 7000 mAh
Design Energy = 14000 mWh
Cell Charge Voltage T1-T2 = 2300mV
Cell Charge Voltage T2-T3 = 2300mV
Cell Charge Voltage T3-T4 = 2300mV
VOLSEL = 1 (external voltage divider)
GNDSEL = 1 (GND of circuit in PACK-)
TEMPS = 1 (external temperature sensor)
Numbers of series cell = 6
Flash Update OK Cell Volt = 1000mV
Load Select = 3
Load Mode = 1
Cell Terminate Voltage = 1750mV
Cell Term V Delta = 100mV
Qmax Cell 0 = 7000mAh
After making the configuration I program the CHEMID equal to 808, according to the battery I am using which is a YUASA 12V 7AH NP7-12. FInally, I made the calibration of this learning cycle process as follows:
Step1:
I start the process with a full charged battery (100%) and relaxed for an hour after it have been charged . I execute IT_ENABLE and then RESET command since the BqStudio. After sending this commands, RUP_DIS is enabled(red), QEN is enabled(red) too. (QEN remains in this configuration during the whole process)
Step2:
After sending IT_ENABLE and RESET. I proceed to discharge the battery to a 1A approximately, what is equivalent to C/7 (where C is the capacity of the battery). Actually, the current is variant and it changes between 900mA and 1100mA during the whole discharging process. When the voltage is high the current is 900mA and when the voltage is low, the current is 110mA. This condition takes place since the 12,8V until the 10.5V approximately. Then, the charging current decrease until 400mA approximately and it remains in this value until the battery’s voltage is 9.3V. The termination voltage is 10.5V However, I maintain this process until 9.3V because of the fact that when I disconnect the battery, the voltage increase considerably. This is a recommendation I got from the specifications of the bq34z110 chip.
Step3:
Once the battery’s voltage is 9.3V, the load is disconnected and the battery is leaved in a relaxed state. In other words, the battery is without load, or with the charger connected to to the battery. The battery is leaved in that way, until the OCVTAKEN bit is set (red). In this time, the RUP_DIS bit is disabled(green). It is recommended to leave the battery to relax 5 hours as minimum. However, I just wait until the OCVTAKEN is set to 1, and it takes just 2 hours approximately.
Step4:
I connect the charger to the battery. Previously, I configure the charger to a charging voltage of 13.8V and limiting the charging current to 1.7A. Due to the fact that I configured the chip with the FC SET% = -1, this FC bit is set (red) when it accomplish the TAPER CURRENT condition, which has a value of 100mA. The discharging process takes 9 hours and when the FC bit is set(red) I disconnect the charger due to this condition.
Step5:
After the FC bit is set to 1(red). I proceed to disconnect the charger and the battery is leaved in a relaxed state until the OCVTAKEN bit is set to 1(red). It happens after 40 minutes approximately. Although it is recommended to leave the battery to relax for 2 hours, I just wait until the OCVTAKEN is set to 1(red). As I am working with a PbA battery, in this stage of the process the maximum error continues in 100% and the Learning Status remains in 4, in other words, these values are not updated.
Step6:
The next step is to connect the load to the battery. The battery is discharged until C/7 what is equivalent to 1A. Although, this value varies between 900mA and 1100mA since the beginning of the discharge until 10.5V. (This has been already explained in the step 2). When the voltage is 9.3V, la current that the load consumes is 400mA. At this point, the load is disconnected from the battery and the battery is leaved to relax.
Step7:
The battery remains in a relaxed state until the OCVTAKEN bit is set(red). It takes 40 minutes since the disconnection of the load. At this point, the maximum error changes to 3% and the Learned Status changes to 5. I understand that when I am using a PbA battery, it is normal that those values get updated during the discharge. In the case of other chemicals, these values should be updated during the charging stage. Although. I am not so sure about it, that is what I supposed, I just have worked with PbA batteries until now.
Step8:
I repeat the steps 4 and 7 one more time until the maximum error is 1% and the Learned Status is equal to 6. In both charging processes the FC bit set(red) when the CURRENT TAPER (100mA) condition is accomplished(FC SET% = -1)
At this point I finalized the learning cycle process. The LOAD MODE parameter was configured for CONSTANT CURRENT. However, my load is a POWER CONSTANT load.
I proposed to develop the learning cycle by changing the LOAD MODE value from 0 to 1(which corresponds to POWER CONSTANT) and doing this, I get the following problem in the Step4: The FC bit never set and I dont know why, the charger current in this point is less than taper current and the SOC is 100%. I don’t know if FC bit set is a necessary condition. I have read some publications in which the learning cycle process procedure of PbA batteries doesn’t mention the FC bit during the charging stage. The procedure just looks for charging to 100% of SOC, and then it waits until the OCVTAKEN is set. I would like you to help me to solve this doubts. Thanks.
My data Memory.
