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Original question:

BQ34Z100-R2: BQ34Z100 shows a steady and accurate SOC while charging up to 100% but immediately drops to 0% after reaching...

BQ34Z100-R2: Incorrect SOC after loading golden image onto new PCB

Swapneel Bose
Prodigy 40 points
Part Number: BQ34Z100-R2

We have done a successful learning cycle and loaded the golden image onto a new set of PCB's for mass production of BMS for drones. Our battery packs are 50V, 30Ah capacity batteries. For loading the golden image we perform the following steps:

1. Load the golden image

2. Perform current calibration, CC and board offset 

3. Send commands RESET, IT ENABLE and SEAL.

4. Put the new gauge through two charge-discharge cycles

The issue:

We have noticed that a few of the fuel gauges start showing incorrect SOC readings during discharge, while others show correct readings. For example, in our drone, which uses two battery packs, in Ardupilot, one of them shows correct SOC readings while the other abruptly starts dropping the SOC values during discharge. Both batteries are drawing the same amount of current and their voltages are the same but the SOC differ. One of the battery packs shows a stable SOC while the other starts dropping SOC very quickly. 

This issue has happened for many different fuel gauges out of all the ones which have been bult for mass production, 

  • 0
    TI__Genius 12215 points

        Have you tested the gauges see SOC drop in Lab with electronic load? Have the SOC drop replicated in Lab?

        If the gauge with the SOC suddenly dropped in the drone but works well in lab test, then it might be caused by some reset event when the drone is flying. You can check if the power supply to the REGIN is stable when the drone transitions between the states like sudden lifting and smooth flying or floating to sudden accelerate. Input voltage fluctuating could reset the gauge and causes the SOC to be 0 accordingly

  • 0 in reply to Steven Yao
    Prodigy 40 points

     

    Steven Yao said:
        Have you tested the gauges see SOC drop in Lab with electronic load? Have the SOC drop replicated in Lab?

    Yes, we have discharged with a DC load at the same rates and no such drop in SOC was noted. 

    We have done a thorough analysis and have realised that only some fuel gauges show this abrupt drop. We are noticing many unusual activities on the fuel gauge:

    1. Some gauges, not all of them, show SOC as 1% even at full charge. Or at times, they show 100% at the lowest voltage, i.e, fully discharged. Whereas, other fuel gauges show perfect and steady readings.

    2. On such incidient, a fuel gauge was showing 1% SOC at full charge and about 10mins into the flight, the SOC jumped to 99% and started decreasing at a steady rate. 

    3. Some battery packs, which were kept at storage voltage of 44V - 50%SOC were shelved for a few weeks and when we returned to check the readings, the SOC would be around 10-20% even though the battery is still in storage voltage. 

    Is there some kind of relation as to why these fuel gauges are behaving like this? 

    |regards,

    Swapneel

  • 0 in reply to Swapneel Bose
    TI__Mastermind 25665 points

    Hi Swapneel,

    Sorry for the delay.

    Is it possible for you to send us your .gg file?

    Regards,

    Evan