in fuel gauge, State of Charge is wrong until a power cycle

RE: in fuel gauge, State of Charge is wrong until a power cycle

Tharaka — Fri, 20 Feb 2026 07:27:24 GMT

Hi

Your symptoms are consistent with an issue in NCS v3.1.0, where an upstream change inverted the current polarity reported by the PMIC driver. Because of this, the fuel gauge sample in that version feeds the wrong sign into the fuel‑gauge algorithm.

When the sign is flipped, the FG interprets discharge current as charging, which keeps the SOC near 100% even while the device is under load.
A PMIC power‑cycle resets the internal FG state, so the SOC suddenly jumps to the correct value — this matches exactly what you are seeing.

This was corrected in NCS v3.1.1.

If you use v3.1.0, you must manually flip the sign of the measured current before calling
nrf_fuel_gauge_init() and nrf_fuel_gauge_process().

You can also see how this is handled in the updated sample here:

https://github.com/nrfconnect/sdk-nrf/blob/main/samples/pmic/native/npm13xx_fuel_gauge/src/fuel_gauge.c#L191-L193

After applying the correct sign, the SOC will behave normally without requiring a PMIC power cycle.

Let me know if you need any help further.

Regards

Tharaka

RE: in fuel gauge, State of Charge is wrong until a power cycle

kruenheck — Thu, 19 Feb 2026 20:00:09 GMT

After more investigation, the problem seems to be that the SOC increases when the board is under load and not charging. A power-cycle (which includes the pmic) brings the SOC down to where we expect it to be. But re-flashing (my way of rebooting the code) doesn't affect the SOC.

RE: in fuel gauge, State of Charge is wrong until a power cycle

kruenheck — Thu, 19 Feb 2026 14:24:32 GMT

Hello. We're using an Npm1300, and the battery, a Renata ICP521630PM has been profiled.

RE: in fuel gauge, State of Charge is wrong until a power cycle

Carl Richard — Thu, 19 Feb 2026 12:24:04 GMT

Hi kruenheck!

Thanks for reaching out. I will ask the guys working with the fuel gauge about this. Some questions to give us more information:

I guess you are using an nPM-device on your board as well, if so, which?
Has the battery been profiled or are you using a standard profile?

Best regards,
Carl Richard