BQ27741-G1: Issue on Remain Capacity and remain capacity

  Taper current could be C/10 (as yours 0.1C) or smaller like C/20, it's the current threshold for stop charging.

  Usually, the gauge can work independently with any charger system. Can you share your schematics to check if the gauge works for your dual charging system?

 Thanks!

Phil

Hi Phil,

find attached a screen shot from the power supply

The LiOn Battery is connected to U11

  Schematics review comments below:

1. Please double check with 2 charger devices if their outputs (+BATT_OUT) can be connected together, or need "OR" circuit;
2. Connecting SRP to battery pack+ makes charging current negative, it may cause current calibration error if using TI bqStudio software;
3. Filter is necessary for SRP/SRN input if accurate measurement is expected, since the voltage over the sense resistor is very small.

    Please check the EVM design for comments 2, 3.

  Thanks!

Phil

 

1. I will check that

I bought the booster fuel tank board and I did my circuit same as here

I don't want to use Ti software since I have my own using msp432 or cc2650.

What are the right values of taper rate and taper current ?

Do I find this values on the battery technical documents? You

Hi Phil,

I just saw that I selected a wrong part. It is BQ7441 instead of BQ27741. Sorry for that. So in its data sheet I don't need a filter It I saw that I am missing a capacitor on Bat pin

Hi Phil,
i add the capacitor and the voltage measuring is correct now, but battery charge state and remain capacity are not correct.
The current consumption is also not so accurate. The multimeter shows 2.5mA and the BA27441 gives me 0mA. Once my circuit consumes 14mA it gives exactly 14mA.
1- Does the battery charge state and remain capacity depens on the taper current and taper rate?

2- Most of the time, the BQ25504 will charge the battery, so i think i should set the current taper according to him. The over voltage is set to 4.2V. Once it reaches this voltage i dont know if the IC has a current charge at this state or if the output current charge is simply 0mAh. If it is zero than the Taper rate will be a very big number.

TI doesn't have the BQ7441 gauge. Please double check again. 

Thanks!

Phil

Hi Phil,

here is the gauge BQ27441-G1

Hi Phil,

the gauge looks like it is working after a few minutes when i charge the battery.
Once i disconnect the battery and plug it back in, the remain capacity and battery level are 0.
If i wait for a few seconds, the values are non 0 and correct.
Does the gauge has a init time at beginning so that the values are measured correctly?
If so than everything looks fine.

  Have you done Host System Calibration? 

  The gauge needs host control including Learning Cycle and Calibration. set the taper current between C/10 to C/20 is recommended. If charging termination voltage is 4.2V, then the charging mode will change from CC to CV when approaching 4.2V and stop charging when the taper current setting reached. 

Thanks!

Phil

Yes, the gauge needs some learning from the battery.
Thanks!
Phil

Hi Phil,
i am using the same code as in Fuel Tank Booster pack code for MSP432. I dont think this example does the battery calibration.

If i calibrate the sensor it will improve the accuracy of the measurements right?
But i am happy with the measurements results without calibration too.
Do i have to calibrate the sensor all the time when the board power cycle?

I cannot do the current calibration beacuse i cannot set a constat current on load on the board all the time:
"The CC Gain and CC Delta are two calibration parameters of concern for current calibration. A known load, typically 1000 mA, is applied to the device during this process"

Same thing on temperature: "A known temperature must be applied to the device for temperature calibration"

DOes the sensor comes with fabric calibration already?

The purpose of calibration process is to offset board traces resistance and sense resistor inaccuracy, it's needed only to improve the accuracy of the measurements, not necessary if the accuracy is good enough.

Hi, Michael,
Is everything working as expected now?

Thanks!
Phil

Hi Phil,

the BQ27441 Gauge is working fine.
Thanks for asking, you can close this thread.

Michael

Hi, Michael,

   Please help to close this thread by marking it "answered".

Thanks!

Phil