nPM1300 fuel gauge SoC

[garrettb]

Hi

Setup: nPM1300, nRF54L15-based board, SDK 2.9.2

I am trying to figure out how to use the nPM1300.

So far, I have not succeeded. Quite frequently, after power cycling my device, the SoC read from the fuel gauge, after rebooting, is quite different (e.g. 20% difference) from the SoC before power down.

My code calls nrf_fuel_gauge_process() every 100 ms.

ret = read_sensors(charger, &voltage, &current, &temp, &chg_status);
:
soc = nrf_fuel_gauge_process(voltage, current, temp, delta, charging_active, NULL);

Some of the things I have tried…

ONE

Simple usage.

Provide no further information to the fuel gauge.

On power up, initialise the fuel gauge straight away.

ret = read_sensors(charger, &p.v0, &p.i0, &p.t0, &chg_status);
:
sensor_channel_get(charger, SENSOR_CHAN_GAUGE_DESIRED_CHARGING_CURRENT, &v);
:
nrf_fuel_gauge_init(&p, NULL);

TWO

Same as ONE, except wait 30 seconds before initialising

THREE

When the SoC reaches 100%, re-initialise the fuel gauge:

int ret = read_sensors(charger, &p.v0, &p.i0, &p.t0, &chg_status);
:
nrf_fuel_gauge_init(&p, NULL);

FOUR

After a few seconds after powering up, read the V,I,T

ret = read_sensors(charger, &p.v0, &p.i0, &p.t0, &chg_status);

then initialise the fuel gauge using these values

FIVE

Save V,I,T values to Flash on a regular basis, and on power-up, restore these  saved values and use them to initialise the fuel gauge.

SIX

Maintain an array of saved V,I,T values (e.g. size 120), and save the average of this circular array to Flash every so often (e.g. every 2 minutes for test purposes).
On power-up, restore these saved averages, and use them to initialise the fuel gauge.

FURTHER INFORMATION

In all cases, there is often quite a large drop or rise in the SoC after power cycling the device.

Here is a sample of the output while charging / discharging (from two separate logs).
One thing of note: the voltage and current fluctuate quite a bit during discharge.

Charging:

[00:13:31.976,257] : delta: 0.100000, V: 4.233, I: -0.019, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2122, Chging 1, Conn 1, ChgSt 17
[00:13:32.076,293] : delta: 0.100000, V: 4.233, I: -0.017, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2095, Chging 1, Conn 1, ChgSt 17
[00:13:32.176,239] : delta: 0.100000, V: 4.233, I: -0.018, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2107, Chging 1, Conn 1, ChgSt 17
[00:13:32.276,275] : delta: 0.100000, V: 4.233, I: -0.017, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2092, Chging 1, Conn 1, ChgSt 17
[00:13:32.376,312] : delta: 0.100000, V: 4.233, I: -0.017, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2091, Chging 1, Conn 1, ChgSt 17
[00:13:32.476,379] : delta: 0.101000, V: 4.233, I: -0.019, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2115, Chging 1, Conn 1, ChgSt 17
[00:13:32.576,293] : delta: 0.099000, V: 4.233, I: -0.018, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2101, Chging 1, Conn 1, ChgSt 17
[00:13:32.676,300] : delta: 0.100000, V: 4.233, I: -0.017, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2087, Chging 1, Conn 1, ChgSt 17
[00:13:32.776,367] : delta: 0.101000, V: 4.233, I: -0.017, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2085, Chging 1, Conn 1, ChgSt 17
[00:13:32.876,312] : delta: 0.099000, V: 4.233, I: -0.019, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2110, Chging 1, Conn 1, ChgSt 17
[00:13:32.976,348] : delta: 0.101000, V: 4.233, I: -0.018, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2096, Chging 1, Conn 1, ChgSt 17
[00:13:33.076,385] : delta: 0.100000, V: 4.233, I: -0.017, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2081, Chging 1, Conn 1, ChgSt 17
[00:13:33.176,330] : delta: 0.099000, V: 4.228, I: -0.018, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2093, Chging 1, Conn 1, ChgSt 17
[00:13:33.276,336] : delta: 0.100000, V: 4.233, I: -0.017, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2079, Chging 1, Conn 1, ChgSt 17
[00:13:33.376,403] : delta: 0.101000, V: 4.233, I: -0.019, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2103, Chging 1, Conn 1, ChgSt 17
[00:13:33.476,348] : delta: 0.100000, V: 4.228, I: -0.018, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2090, Chging 1, Conn 1, ChgSt 17
[00:13:33.576,354] : delta: 0.100000, V: 4.233, I: -0.018, T: 25.82, SoC: 98.59, TTE: nan, TTF: 2088, Chging 1, Conn 1, ChgSt 17
[00:13:33.676,452] : delta: 0.100000, V: 4.233, I: -0.019, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2100, Chging 1, Conn 1, ChgSt 17
[00:13:33.776,367] : delta: 0.100000, V: 4.228, I: -0.018, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2086, Chging 1, Conn 1, ChgSt 17
[00:13:33.876,342] : delta: 0.100000, V: 4.233, I: -0.016, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2057, Chging 1, Conn 1, ChgSt 17
[00:13:33.976,470] : delta: 0.100000, V: 4.233, I: -0.019, T: 25.93, SoC: 98.59, TTE: nan, TTF: 2096, Chging 1, Conn 1, ChgSt 17
[00:13:34.076,354] : delta: 0.100000, V: 4.228, I: -0.018, T: 25.93, SoC: 98.60, TTE: nan, TTF: 2082, Chging 1, Conn 1, ChgSt 17
[00:13:34.176,361] : delta: 0.100000, V: 4.233, I: -0.018, T: 25.93, SoC: 98.60, TTE: nan, TTF: 2081, Chging 1, Conn 1, ChgSt 17
[00:13:34.276,428] : delta: 0.100000, V: 4.233, I: -0.018, T: 25.93, SoC: 98.60, TTE: nan, TTF: 2079, Chging 1, Conn 1, ChgSt 17
[00:13:34.376,373] : delta: 0.100000, V: 4.233, I: -0.017, T: 25.93, SoC: 98.60, TTE: nan, TTF: 2065, Chging 1, Conn 1, ChgSt 17
[00:13:34.476,379] : delta: 0.100000, V: 4.233, I: -0.018, T: 25.93, SoC: 98.60, TTE: nan, TTF: 2077, Chging 1, Conn 1, ChgSt 17

Discharging:

[00:14:18.076,660] : delta: 0.100000, V: 3.994, I: 0.011, T: 26.03, SoC: 96.79, TTE: 15040, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:18.176,727] : delta: 0.100000, V: 3.984, I: 0.023, T: 26.03, SoC: 96.79, TTE: 15039, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:18.276,794] : delta: 0.100000, V: 3.994, I: 0.023, T: 26.03, SoC: 96.79, TTE: 15039, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:18.376,678] : delta: 0.100000, V: 3.989, I: 0.067, T: 26.03, SoC: 96.79, TTE: 15039, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:18.476,745] : delta: 0.100000, V: 3.989, I: 0.019, T: 26.03, SoC: 96.78, TTE: 15039, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:18.576,812] : delta: 0.100000, V: 3.999, I: 0.021, T: 26.03, SoC: 96.78, TTE: 15038, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:18.676,696] : delta: 0.100000, V: 3.989, I: 0.023, T: 26.03, SoC: 96.78, TTE: 15038, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:18.776,763] : delta: 0.100000, V: 3.994, I: 0.019, T: 26.03, SoC: 96.78, TTE: 15038, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:18.876,922] : delta: 0.100000, V: 3.999, I: 0.039, T: 26.03, SoC: 96.78, TTE: 15038, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:18.976,715] : delta: 0.100000, V: 4.003, I: 0.043, T: 26.03, SoC: 96.78, TTE: 15037, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:19.076,782] : delta: 0.100000, V: 3.994, I: 0.011, T: 26.03, SoC: 96.78, TTE: 15037, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:19.176,940] : delta: 0.100000, V: 3.999, I: 0.067, T: 26.03, SoC: 96.78, TTE: 15037, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:19.276,733] : delta: 0.100000, V: 3.994, I: 0.023, T: 26.03, SoC: 96.78, TTE: 15037, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:19.376,800] : delta: 0.100000, V: 3.984, I: 0.022, T: 26.03, SoC: 96.78, TTE: 15036, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:19.476,959] : delta: 0.100000, V: 3.994, I: 0.035, T: 26.03, SoC: 96.78, TTE: 15036, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:19.576,812] : delta: 0.100000, V: 4.003, I: 0.022, T: 26.03, SoC: 96.78, TTE: 15036, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:19.676,788] : delta: 0.100000, V: 3.994, I: 0.019, T: 26.03, SoC: 96.78, TTE: 15035, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:19.776,947] : delta: 0.100000, V: 4.003, I: 0.021, T: 26.03, SoC: 96.78, TTE: 15035, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:19.876,861] : delta: 0.100000, V: 3.994, I: 0.021, T: 26.03, SoC: 96.78, TTE: 15035, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:19.976,837] : delta: 0.100000, V: 3.994, I: 0.009, T: 26.03, SoC: 96.77, TTE: 15035, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:20.076,995] : delta: 0.100000, V: 4.003, I: 0.039, T: 26.03, SoC: 96.77, TTE: 15035, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:20.176,879] : delta: 0.100000, V: 4.003, I: 0.020, T: 26.03, SoC: 96.77, TTE: 15034, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:20.276,855] : delta: 0.100000, V: 3.994, I: 0.019, T: 26.03, SoC: 96.77, TTE: 15034, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:20.377,014] : delta: 0.100000, V: 3.994, I: 0.021, T: 26.03, SoC: 96.77, TTE: 15034, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:20.477,020] : delta: 0.100000, V: 3.989, I: 0.019, T: 26.03, SoC: 96.77, TTE: 15034, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:20.576,843] : delta: 0.100000, V: 3.999, I: 0.019, T: 26.03, SoC: 96.77, TTE: 15033, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:20.677,032] : delta: 0.100000, V: 3.994, I: 0.039, T: 26.03, SoC: 96.77, TTE: 15033, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:20.776,885] : delta: 0.100000, V: 3.994, I: 0.011, T: 26.03, SoC: 96.77, TTE: 15033, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:20.876,922] : delta: 0.100000, V: 3.999, I: 0.021, T: 26.03, SoC: 96.77, TTE: 15033, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:20.977,050] : delta: 0.100000, V: 4.003, I: 0.019, T: 26.03, SoC: 96.77, TTE: 15032, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:21.076,934] : delta: 0.100000, V: 3.994, I: 0.039, T: 26.03, SoC: 96.77, TTE: 15032, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:21.176,940] : delta: 0.100000, V: 3.989, I: 0.019, T: 26.03, SoC: 96.77, TTE: 15032, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:21.277,069] : delta: 0.100000, V: 3.999, I: 0.019, T: 26.03, SoC: 96.77, TTE: 15032, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:21.377,075] : delta: 0.100000, V: 3.994, I: 0.019, T: 26.03, SoC: 96.77, TTE: 15032, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:21.476,959] : delta: 0.100000, V: 3.979, I: 0.043, T: 25.62, SoC: 96.77, TTE: 15031, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:21.577,087] : delta: 0.100000, V: 4.003, I: 0.019, T: 26.03, SoC: 96.77, TTE: 15031, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:21.677,062] : delta: 0.100000, V: 3.999, I: 0.022, T: 26.03, SoC: 96.77, TTE: 15031, TTF: nan, Chging 0, Conn 0, ChgSt 0
[00:14:21.776,947] : delta: 0.100000, V: 3.999, I: 0.009, T: 26.03, SoC: 96.76, TTE: 15031, TTF: nan, Chging 0, Conn 0, ChgSt 0

Question: Do you have any suggestions on how I could get more reliable SoC values from the chip?
Question: Is there a maximum interval between nrf_fuel_gauge_process() calls (i.e. a maximum delta) beyond which the update is not reliable (e.g. 500 ms?)
Question: Does the fuel gauge algorithm average its input over time?

Thanks

[Simonr]

Hi Garrett

It still seems like you're using the old convention for the nrf_fuel_gauge_process() function. Please try using a negative current variable and see if the issue still occurs.

nrf_fuel_gauge_process(voltage, -current, temp, delta, NULL);

Best regards,

Simon

[garrettb]

Hi Simon,

Am I not using the newer convention?

My code is detailed above, but here is the important part:

ret = read_sensors(charger, &voltage, &current, &temp, &chg_status);
	:
current = -current;
	:
soc = nrf_fuel_gauge_process(voltage, current, temp, delta, NULL);

The value "current" is inverted before making the call to nrf_fuel_gauge_process().

And, as I say, this seems works all the time, except when I re-Flash the system again.

[Simonr]

Hi Garrett

I'm sorry about the late update. Audun will get back to you when we have reproduced this on our end. Thank you for your patience.

Best regards,

Simon