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Original question:

BQ35100: Unreliable SOH in EOS mode

BQ35100: Mechanism to follow to read EOS

santhosh kumar nallamalla
Prodigy 20 points
Part Number: BQ35100
Other Parts Discussed in Thread: BQSTUDIO

Hi,

We are trying to use BQ35100 fuel gauge IC in our product to check the remaining percentage of Tadiran TL5930 (19000mAh) battery. Am new to this Power management field. I have below doubts. 

1. This battery TL5930 is not listed in the Chemistry IDs. Can we use TL-4930 (1900mAh) ?

2. We calibrated the battery and programmed it with Chemistry ID 0608 of TL-4930. And we configured it into EOS mode. Here we are having few confusions. 

a. As per the data sheet SLUSCM6E 8.2.2.2.1.2, it is mentioned that we have to give Gauge_Start() 1s prior to the high load pulse starting in Step 3. Here can I know what is this high load pulsing exactly means ?

b. In the step 4, it is again mentioned that we have to give Gauge_Stop() directly after the high load pulse has stopped. How we will know when it is stopped ?

3. In EOS mode, at what rate we should read the battery percentage. Like every 1 hour or every 24 hours ?

4. In EOS mode, do we need to control the load ? -- In our design, we are using a BLE Module which is having on board i2c interface to which this BQ35100 is connected. So to this battery this BLE module only acts as a load in which our application is running and communication with the BQ35100 is also done by BLE module only. 

4. What exactly high load pulsing means ?

5. On turning on the device, can we read the SOH in EOS mode ?

6. With BQ Studio software can we monitor how the Battery is getting consumed by connecting a fixed load to the battery ?

  • 0
    TI__Guru* 76230 points

    1. What mode are you trying to use the gauge in. If accumulator mode or EOS mode, yes you can use that id. If SOH mode, no you can't.

    2. a. High load pulse is simply your load turning on

    b. Your host controlller will know when the load is about to be turned on or off. Most applications that use this are applications where there is data transmission wirelessly. Before the radio wakes to turn on, your host should know and send the gauge start.

    3. You determine how often to read the SOC/SOH. Note that in EOS mode, the SOC reported may not be very accurate as the gauge is determining SOC based off the resistance profile. If you plan on reading SOC, then you will need the actual ID generated for your cell.

    4. The BLE radio and whatever else is connected to the battery (meter) will be the load.

    5. High current draw from your load, i.e the radio and/ the smart meter.

    6. If you have the correct chem id, and after the gauge has taken the correct resistance measurements, then you should be able to read the SOH.

    7. You can monitor current  being drawn  from the battery via bqstudio using a fixed load .

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 20 points

    Hi Onyx,

    Thanks for your response. It helped me to understand better. 

    But still I have few more doubts. 

    1. In my application, the load is when the ble module advertises or scan or connects with a Mobile application. My module advertises continuously every 1s and scans continuously. Our application runs standalone and should be operating for years. We chose TL5930 19Ah Battery for this reason. The device will be always in high load only. So in this scenario which mode is better to use ?

    2. In accumulator mode also do we need to control the load ?

    3. Our requirement is to know how much percentage of battery is remaining only. So can we proceed with any other modes than EOS without load controlling ? 

    4. If you have any C library for this BQ35100 please share with us. 

  • 0 in reply to santhosh kumar nallamalla
    TI__Guru 60846 points

    #1: These are two distinct use cases, which are up to the customer to decide. If you want to know how much charge was already drawn from the battery, then ACC mode is appropriate. The drawback is that you must make sure that the gauge is on whenever a load current is turned on. There's also a limit how often the gauge can power cycle in this mode as the flash memory will wear out eventually (see the caution box in 5.1.1 http://www.ti.com/lit/ug/sluubh1c/sluubh1c.pdf).

    EOS on the other hand will measure how the cell impedance changes. So this doesn't depend on the coulomb counter not missing any load current and may be easier to implement in a system.

    #2: No

    #3: This will require ACC mode. You can use AccumulatedCapacity and cell design capacity to determine percentages.

    #4: We don't have an official C library for this gauge.