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bq27501 EVM and BQEasy

Nykka Rumbaoa
Prodigy 20 points
Other Parts Discussed in Thread: BQ27501

I have been trying for months to get my golden DFI files and have failed every single time even with local support from our TI FE.

  • I am using an external 2.5V to power up my EVM board. 
  • When both the load and charger are both off, and battery is attached to the EVM. There is a ~60mA current being drawn out of my battery.   I've also verified this number with an external DMM.

  

  •  The first step in the learn cycle requires me to do a discharge and wait 5 hours:
  • I've discharged to 3.3V and turned off my load.  (I've also attempted this on another try with a load circuit and detached the load from the EVM).  Minimum rated cell voltage for my battery is 3.0V.
  • After a 5 hour wait period, because current is still being drawn from my battery (either due to battery discharging on it's own or the EVM pulling current out), my battery always get overdischarged to the point where the battery shuts off.
  • This also presents a problem during the charge step.  When the FC flag gets set (battery is fully charged), I detached my charger and wait 2 hours.  After the 2 hours, however, the FC flag gets reset because the battery is no longer fully charged due to the constant 60mA current being drawn out from the battery.
  • Is this a known problem or is this more related to my EVM board?  I have two bq27501 boards and they both behave the same way.  It's getting to the point where it is becoming very painful to start a learn cycle over.  Any advice is greatly appreciated. 
  • 0
    TI__Intellectual 2340 points

    Can you confirm that if you remove the load and charger connections but still maintain the battery connected, that you still have the 50mA draw?

  • 0 in reply to MikeV
    Prodigy 20 points

    Hi Mike.  Here is what my findings are:

    • When load or charger is just turned OFF, I still see the 60mA current draw.
    • When I took the load out of the picture, there was no difference.
    • When I took the supply (charger) out of the picture, the current went back down to zero.  So I tried a different power supply but got a higher current drawn when the power supply is in the OFF state.  The power supply (+) is attached to Charger (+) and the power supply (-) is attached to charger (-) on the EVM board. 
  • 0 in reply to Nykka Rumbaoa
    TI__Intellectual 2340 points

    If your charger is simply a power supply then I can see that when shut off it has low impedance. The best way to stop charging then would be to actually disconnect the power supply from EVM once charge is complete. You would not experience this with an actual charger EVM.