• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 63 subscribers
  • Views 379 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

BQ20Z655-R1: Charge Enable doesnt work.

BQ20Z655-R1: Chg mosfet turns on late while discharging.

user5503575
Intellectual 800 points
Part Number: BQ20Z655-R1

Hi,

(I asked similar question before. I have focused Chg mosfet while discharging mode. You can see my log files in the attachments.) 

I have two same batteries which use Charge Enable function. 

I charge them to full and they terminate. Chg mosfets are turned off because of charge termination. Then I left them relaxing.

When I want to discharge this batteries, one of them turns chg mosfet on immediately, but the other one turns on 15seconds later. So current flows on chg mosfet body diode. Then it heats up.
Which points should I focus on data flash? Why same batteries behaves different?

If I want to discharge my batteries with high current, my chg mosfets burns because the current flows on my chg fet body diode.

Why chg fet turns on late?

  • 0
    TI__Guru 52115 points

    I don't see any log files.   Could you provide them? Also,  provide your gg file as well.

    Andy

  • 0 in reply to Andy Liu (BMS)
    Intellectual 800 points

    You can see  the pack voltages for my 4 series battery packs in the pictures.

    Firstly, Batteries were full charged so chg mosfet was off and we can see that 0.5V voltage drop on chg mosfet. Pack voltage is 16.8V but we can see 16.8-0.5=16.3V. (By the way, they are all same batteries. They behave different on every discharge.)

    Then I have been started to discharge batteries, the voltage drop was keeps going for more than 10 seconds. Then it turns on.

    In normal operation, chg mosfets must turns on when I start to discharge batteries.

    Because of this chg mosfet turning on delay, my current flows on chg mosfet body diode and my chg mosfets blows in first 10 seconds of discharging.

    I will attach my log file and gg file.

  • 0 in reply to user5503575
    TI__Guru 52115 points

    Let us know when are log and gg files are ready. Thanks.

    Andy

  • 0 in reply to Andy Liu (BMS)
    Intellectual 800 points

    Hi Andy,

    I have been working on my battery and problem has been fixed.

    I have noticed that my battery turned chg mosfet on without any delay when I connect SMBUS.

    Then the thought struct me that when I connect to battery with smbus, battery is not on sleep mode and chg mosfet behaves fast :)

    So I researched and found that there is a register(POWER=>Wake current register.) which sets the behavour battery when it is in sleep mode. I had left this register as default  before so my battery didnt check the current to wake up while in sleep mode. It was waiting to 20second to wake up automatically.

    In this period of time, current was flowing through my chg mosfet body diode and it blows up. Then IC wakes up from sleep mode and check the current. Then it says "Omg whats going on :/ Currents flows so I have to turn mosfets on." But it was too late :)

    I had set this register 01 and everything is okey now :)

    Thank you!