Unexpected high current draw on LiPo Fuel Gauge

Components & Accessories Power
1

Hello,

I’m experiencing a (in relation) high current draw of 0.9 mA when the LiPo fuel gauge is connected to the battery and the attached NodeMCU is in deep sleep.

My setup is very simple: NodeMCU, connected to a LiPo batter with an MCP1700 LDO converter. In parallel to the battery i attached the fuel gauge. The only connection between the NodeMCU and the fuel gauge are SDA, SCL and GND.

My code reads the values from the fuel gauge and goes to deep sleep for some time, wakes up, takes a reading and goes to sleep again. Everything is working so far, readings are good.

But, the deep sleep current rose from 0.03 mA without the fuel gauge to 0.9 mA. The specs of the MAX17043 is talking about 0.05 mA operating current. So this seems a bit high and would have a huge impact on battery life.

I now tried to investigate, where this current draw comes from:

  • If i remove the battery lead from the lipo fuel gauge, the current draw drops down to 0.03 mA

  • If i leave the battery attached and remove the i2c connections there is no change

  • If i leave the battery attached but do not connect the i2c cables at all, i get a current draw of aroung 0.08 mA - which seems to my deep sleep current and the added 0.05 mA operating current of the fuel gauge.

Currently i have no idea, what could cause this current draw. For me it seems, that the usage of i2c with the MAX17043 causes this current draw, while the current is not flowing over the i2c cables to the nodemcu. So my guess is the current is flowing inside the fuel gauge module somehow, but i have no idea where and how to suppress this.

Maybe one of you guys have had this issue and has an idea how to get rid of it. I will go and try another fuel gauge as well, maybe one of the components is faulty - even if i get correct readings.

Best

mojo

If I do not

2

Hi mojo2600,

Most likely, that excess current is from the pull-up resistors on the I2C lines. You could try removing those and then adding in your own pull-up resistors to reduce that current draw. Another possible source (or, more likely, a concurrent source) would be the pull-up resistor on the CELL pin for monitoring battery voltage. The board is designed to be powered by the attached battery but if you have an alternate power source for Vcc, you could disconnect the CELL line from Vcc by severing the trace or pulling the resistor. You would need to provide 3.3V to Vcc to power the board, though. [This comment goes into that a bit more.

If you are not sure which traces or resistors to pull, the Eagle design files available for download from the “Documents” tab on the [product page. Those can help you identify the correct traces and resistors to adjust.

I hope this helps you get the power draw down to the levels you need for your project.](SparkFun LiPo Fuel Gauge - TOL-20680 - SparkFun Electronics)](https://www.sparkfun.com/products/10617#comment-503313b6ce395f370f000000)