STC3115 Not showing correct SoC after charging

[Sami-Pekka Mähönen]

Posted on September 12, 2017 at 12:02

Hello everyone,

We are having an issue with STC3115 (fuel gauge) where we are charging our device while it is powered off. After powering on the device, SoC received from STC3115 driver to application shows the same value as it was before

charging. Then it takes around 30 minutes or so SoC slowly update to the actual value.

Also to be noted that:

a) If the battery is re-attached, then SoC shows the correct value on first power on after charging

b) When the device is turned off (standby), our application sets fuel gauge to power saving mode

c) SoC is updated correctly when the device charged while being powered on

d) Our hardware does not support charging mode where the device could be woken from standby if the charger is connected

If anyone has faced similar problems or have any ideas how to solve this issue with SoC not updating if the device is charged while powered off, please let us know. We are also happy to give more details if needed.

#stc3115-issue-startup Note: this post was migrated and contained many threaded conversations, some content may be missing.

[Gregory Go.]

Posted on December 13, 2017 at 00:43

Note that you may want to turn off the Gas gauge when your application is also turned off (or in standby), to reduce the gas gauge power consumption.

STC3115 Current consumption in Voltage mode (GG_RUN ==1) : 45uA

STC3115 Current consumption in Standby mode (GG_RUN ==0) : 2uA

STC3115 Current consumption in Power-down mode (Vcc<2.7V) : 1uA

It is up to you to decide how to implement the gas gauge behavior depending on your application.

If your application is in standby for a short time, the battery level won't change a lot, so the gas gauge will see the same battery voltage before and after GG_RUN == 1.

But if your application is in standby for a long time (several days), the battery level will decrease more. So if the gas gauge has been turned off during all this time, when it will wake up, it will consider this battery voltage change as a sudden voltage drop, and it will need some minutes to recover to the correct State of Charge.

An alternative implementation if your device is in standby for a long time:

if you want to keep a system standby mode with low power consumption, but still have an accurate battery SoC when the system wakes up, you need to periodically run (GG_RUN = 1) the gas gauge every days, for few seconds, and then put it back to stop mode (GG_RUN = 0) the rest of the time.

[Tristan Demanuele]

Posted on March 08, 2018 at 12:29

Hi Currently we have the same issue as above and we have tried all the mentioned suggestions. One question, if the application is not running (device off) and device is charging, does the STC3115 still collect battery SoC data? Or does the application need to be running?

Thanks!