BQ27542EVM: SOC rises during relaxation.

The gauge re-calculates SOC based on OCV measurements and temperature. This may cause a rise in SOC, even for correctly configured gauges (e.g. actual SOC indeed rises because of a temperature change).

Please enable smoothing. This will keep SOC constant in relax.

Smoothen is enabled,  RlxSmEn and SMSYNEN are not enabled, but SOC rises in relax.

At the end of discharging, SOC and SOCUnfiltered are 50%. Then SOCUnfiltered reduces, but SOC rises.This phenomenon is very strange.

Filtered SOC increases if a small (non-zero) current causes the coulomb count for filtered Remaining Capacity to change enough for SOC to increase.

Here is Passed Charge (Coulomb Count in mAh) between OCV measurements (which reset Passed Charge, hence it looks like a sawtooth waveform) and filtered Remaining Capacity in mAh:

So over a long time in relax, the gauge "measures" a passed charge that causes filtered Remaining Capacity to increase. Unfiltered Remaining Capacity re-adjusts every time the gauge takes an OCV measurement.

The problem is that the gauge measures a charging current in relax in your case. You current deadband is set to 8mA, hence the gauge will not report this current (passed charge changes by 1mAh in approx. 1000s so that implies almost 4mA of measured current, which is below the 8mA current deadband setting) but if there is a current present, it will adjust coulomb count and that's why you see the increase in SOC.

Hello,

I set SMSYNEN=0 and RlxSmEn=0. According to the TR file, smoothing was not started at this time. During relaxation, SOC should remain unchanged, but it still increases. After 7 days of standing, it increases from 64% to 71%.

My register configuration is as follows. How can I modify it to improve this issue？

I'm looking forward to your reply.

Thank you.

This is likely due to a very small (possibly erroneous) current. It can't be easily fixed other than to disable smoothing.

But the register I set has turned off the smoothing of the relaxation state, but the SOC still rises.

I set SMSYNEN=0 and RlxSmEn=0.

Hi Fenghaiyan,

Have you tried setting SMSYNEN=0 and RlxSmEn=1 ?

Regards,
Jose Couso

Hi Jose,

1、Setting SMSYNEN=0 and RlxSmEn=1 , the SOC fluctuation.

2、SMSYNEN=1 and RlxSmEn=1

3、SMSYNEN=1 and RlxSmEn=0

Hi Fenghaiyan,

Is SmoothEn set in Pack Configuration register? Please disable it if so.


This is so that Unfiltered capacity values re-adjust every time an OCV measurement is taken.

Regards,
Jose Couso