Queries regarding MAXIM Fuel gauge behaviour with given battery characteristics

Semiconductor Integrated Circuits (ICs)
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1

Hi

We are using the fuel gauge along with a battery. Please find the below technical details

Fuel Gauge IC: MAX17201G+T
Current Battery Characteristics:

  1. HW Li-Ion 18650 25000mAH 3.7 V
  2. 92.5 Wh 2019I090003
  3. Width - 114.5mm Max
  4. Height - 70.0mm Max
  5. Thickness - 39.0mm Max
  6. Cable length - 195-205 mm
  7. Capacity - 30000mAh Typical/min
  8. Temperature - 0-45 C (Charge) , -20 to 60 C (discharge)
  9. Standard charge time - 6.5 hr

I have trained the fuel gauge with the above battery and prepared the fuel gauge calibration dataset. Now I am using the same calibrated data set on my device for the fuel gauge. Currently, I am facing issues with the Fuel Gauge output and suspecting the fuel gauge is not working properly.

Can anyone please respond to the below queries,

  1. I am using the same battery as mentioned above, but have added an additional cable attached with a 6A/4A fuse between the battery and fuel gauge to limit the inrush current. Due to the fuse, the cable length is also increased here. Does adding a fuse and increasing the cable length can impact the fuel gauge reading/algorithm? Do I need to perform the training again with this setup to derive the calibration data set?

  2. According to the fuel gauge datasheet, FullCapRep will be calculated at the end of every charge cycle in the application. It’s observed in my device that the fuel gauge was reporting FullCapRep value exactly equal to the RemCap value every time (Battery was not in a charging state). This behaviour is contradicting with the one mentioned in the datasheet. Under what circumstances can it behave like this?

  3. It has been observed that the remaining capacity can drastically reduce from given value to zero with minimum time span. Is this behaviour expected with a properly working fuel gauge? If so, under what circumstances can it behave such?

I would really appreciate the help.
Thank you.

2

Hi,
Welcome to the DigiKey tech forum. I found this article which may be helpful in your application, How to Use The MAX17201/MAX17211 and MAX17205/MAX17215 to Fuel-Gauge Primary Cell Batteries - Application Note - Maxim (analog.com)

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3

Hello,
Here is another article regarding memory space, which may or may not be helpful in your exact case but at the least can be another reference:
Configuring the MAX17205 Fuel Gauge Without Writing to Nonvolatile Memory

4

Hi,

Thank you for your quick response.
I have followed attached documents to calibrate the MAX1720G+T with the new Battery a year back.
MAX17260GEVKIT-MAX17260XEVKIT.pdf (1.3 MB)
MAX17260.pdf (1.9 MB)

5

Herewith attaching snapshot captured after successful calibration which we did a year ago.

Final Register for calibrated MAX17201_121321
Final Register for calibrated MAX17201_1213211175×818 148 KB

Final Configuration for calibrated MAX17201_121321
Final Configuration for calibrated MAX17201_1213211178×822 315 KB

6

I have also prepared an XLS with dataset which we are configuring in NVM (0x180 to 0x1DF). I am flashing the same INI in NVM of MAX1720G+T in our init call which is getting invoke once on every bootup.
INIT_FILE_FOR_NVM.xlsx (5.4 KB)

7

Thank you for your follow up.

You’re going to find the best support for this type of inquiry would be posting a question on Analog Devices EngineerZone Power Management - Q&A which I see you have done.

8

Yes I have. Thank you.

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