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BQ27510EVM: BQ27510-G3

Part Number: BQ27510EVM
Other Parts Discussed in Thread: BQ27510-G3

Tool/software:

We're using a BQ27510-G3 as gas gauge for a battery powered Android device. We have a test that checks the charging current draw (while powered by DC supply) by querying the gas gauge with a 50% and 100% state of charge simulated battery connected. These two conditions are measured sequentially, first the 50% SoC charging current is measured, and then the 100% SoC charging current is measured. We expect the gauge gauge to report 0 mA current when 100% SoC simulated battery is connected.

On a handful of units, the gas gauge reports a very small discharge (about 5000 uA) when the 100% SoC condition is measured. After about 60 seconds, the gauge reports 0 uA, which we expect.

Our terminal charging voltage is 4.1V, and it was found that the battery simulator was incorrectly set to 4.127V for 100% SoC. Setting this to 4.1V seems to have fixed the problem.

I can re-create the reported small discharge by quickly switching from 50% SoC (about 3.7V open circuit), to 100% SoC (4.1V open circuit) and the querying the gas gauge. We're using the circuit design from the datasheet/technical documentation, and I do not see the expected -50uV across the 0.01 ohm sense resistor when the gauge reports -5000 uA. When the gauge settles to 0 uA, there is no obvious change in voltage across the sense resistor.

We're using "/sys/class/power_supply/bq27510g3-0/current_now" to query the gas gauge.

Can anyone explain what might bet happening?

  • Hello, 

    I am wondering if this could be caused by using a cell simulator and not an actual battery to gauge SOC.

    Regards, 

    Robert. 

  • Possible, but it seems more related to switching between voltages quickly, when the 100% SoC voltage is slightly higher than what was programmed. Example, applying 4.127V instead the expected 4.1V for 100% SoC.

    I found another post on the forums saying the gauge reported a "ghost" 4mA when the known draw was only 100uA, which seems similar to what's happening here. But I don't believe they were switching batteries.

    I should check if I can recreate the problem by only applying a higher than expected 100% SoC voltage. Maybe switching batteries/SoC voltages isn't related.

  • Hello Charles, 

    You should be able to change the deadband to account for this "ghost" current. 

    Regards, 

    Robert.