Hi ,
We are using bq20z95 in one of our products, to give accurate pre-alarms to end user, before battery pack dies. As a part of performance analysis of IC. We have conducted few charge/discharge cycles and at same time we logged data for evaluation, from BQEASY software. From the attached log data, we understand that IC is having 20-30% of accuracy problem.
When we were first charging the battery pack we captured the data from bqEASY software. We attached same files for your reference, which is cycle1charge.xls. When you observe the data, we have created one column ‘cumulative charge pumped in’. This column gives us the information about how much of the charge being pumped in mAh. This is calculated with the help of charging current of the batter pack. After completion of charging it shows 3842+300(initial charge before start of charging)=4142mAh is the charge available.
Then, we discharged the battery pack using motor load. We attached the discharge log file, which is cycle1discharge_analysis.xls. In this file also we created two columns which are,
- Remaining Capacity as per current consumption – This gives the information that how much of charge is available in the battery pack calculated based on the current summation.
- Difference in mAh – which gives us the information about difference between Remaining capacity calculated by bqEASY and Remaining Capacity calculated by above mentioned column.
If you observe the data, when ever we remove load and connect it back the Remaining Capacity calculated by bqEASY is changing drastically at that time. You can observe that in marked rows 2978 and 2979.
When you calculate the difference it is going over 950 mAh. Why is it so suddenly Remaining capacity and Full Charge Capacity calculated by bqEASY are changing abruptly?
Similarly. When you observe rows 3970 and 3971 you will understand that Remaining capacity came down to 0mAh from 273 mAh. Average time to Empty is also changed from 29 mins to 0 mins.
The average time to empty is a serious parameter in our application. We expect IC to give precise information about remaining time to empty. But, by observing the discharging cycle we can say that it is not providing precise information. In our product the IC must give alarm 30 mins prior to complete discharge of the battery pack.
We are sending you raw logged files as well in the attachment.
What could be the problem? Please try and help us solve this issue as soon as possible.
Regards,
K.Raghu
0574.cycle1discharge.log3386.cycle1charge.xls0312.cycle1discharge_analysis.xls