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BQ40Z50: Over-discharging battery while at rest

Drew Scott
Prodigy 80 points
Part Number: BQ40Z50
Other Parts Discussed in Thread: EV2400

Hey all,

When performing a learning cycle we allow our batteries to rest for a recommended amount of time found in the learning cycle portion of this document http://www.ti.com/lit/an/slua777/slua777.pdf.

The problem we have run in to is that when left to rest the battery keeps discharging slowly when not attached to any load or other current drain. 

We were curious if anyone had any suggestions, we have tried powering off and disconnecting our load but it seems like overnight the battery will drop .4-.5 Volts below the safe discharge levels for the battery. Has anyone else had problems where other parts drain power? Have they found any solution to it aside from flat-out disconnecting it? The battery, in our case, was connected to the gauge, directly on it, and the gauge was connected to a charger, a microcontroller and an EV2400 unit.

Thanks!

  • 0
    TI__Genius 14985 points
    Hi Drew, perhaps you might do some experiments disconnecting each possible culprit to see if it eliminates the drain.
    Are you using the bq40z50EVM and a charger EVM or is this your own custom board? One possibility might be that the 3.3V I2C pullups inside the EV2400 are creating a current path if you have I2C pullups on your system. Or there might be a ground loop between the PC and other power supply elements through the EV2400/USB.