• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 359 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.

BQ76920: What should I do to charge a battery which is deeply dischaged?

Lu Feiyue
Intellectual 660 points
Part Number: BQ76920
Other Parts Discussed in Thread: BQ76200, BQ78350, BQ24610, , BQ78350-R1

I  use  bq78350 + bq7692000  + bq76200  and the  high-side  driving method  to  immplemented  my design.

 I  use a 5S1P pack. My charger is bq24610.

When I  discharge the batttery to 8V,the module can't provide a output voltage, and my charger can't charge the battery.

I have to press the boot button connected to pin TS1 of bq76920 to charge the battery.

When I  discharge the batttery to lower voltages ,   pressing the boot button connected to pin TS1 of bq76920  can't charge the battery.


I didn't use the circuit used in the document -tidrqy7. And  I  did't use pack monitor function of bq76200.



I want to know  if I discharge a battery pack to a lower voltage ,say 1V,  what I should to do to charge such a deeply discharged battery?

Can I implement my purpose symply using the circuit in the in the document -tidrqy7?

  • 0
    TI__Guru* 81034 points
    Hi Feiyue,

    The BQ78350-R1 has a voltage-based shutdown feature. The default setting for the voltage shutdown is 1750mV, but this can be programmed to a different value in the data flash. When the shutdown voltage is reached, the FETs are turned off which is why charging is not possible. You can see the full description of this feature in Section 8.4.1 of the BQ78350-R1 TRM (Technical Reference Manual): www.ti.com/.../sluubd3

    In Chapter 5 of the TRM, you can see that the BQ78350-R1 does have a pre-charge feature to slowly charge a battery until it is in a safe range for fast charging. This feature requires the use of a pre-charge FET.

    However, you need to understand that it is very dangerous to discharge your cells to the levels you describe. If you are really going down to 1.6 V per cell on a Li-Ion battery pack, this is way below the minimum voltage allowed by the cell manufacturer. At voltages this low, permanent changes happen to the cells that can result in internal shorts and permanent capacity loss. Storing the battery at very low voltages will increase the self-discharge rate. This is why the under-voltage protection feature is very important for safety.

    Best regards,
    Matt