Part Number: BQ40Z50-R2
Hi
I began some tests to learn about the BQ40z50 with the help of the EVM. (I used a power supply for charging and 20 Ohm load for discharging)
My configuration is: 3 Li-ion cells 3.63V/2600mAh. I chosed the chemistry ID which is closest to my cell (ICR18650-26JM) then I did the calibration with BQStudio, enabled FET_EN and started charging. Here're some points I didn't understand:
1) battery starts charging at 0.5A and balancing is working but after a while the CHG mosfet got off and charging current became 0A. That's ok but I didn't understand why. The cells voltage were still far from 4.2V that I set. In addition I set Design Voltage= 10890mv (3x3.63V). Gauge reached 100% SOC ???
2) then I attached a load syncing 0.5A. Discharge began but I had to stop it because 1st cell gaves some problem: after a while, its voltage dropped too low and BQStudio revealed there was an undervoltage fail. In fact cell n. 1 was quite unbalanced, about 100mV lower than the other two.
Anyway I tried to charge the cells again but I didn't succeed to charge at 0.5A as before: I had to reduce the charging current to 0.3A. After a while I increased the current and that worked. Why?
Can somebody help me understand? In particular I didn't understand how can I fully charged and discharged my 3S pack battery. What's missing?
Thanks