Good morning,
I'm currently using the STC3115 in my application for estimating the SOC of a 1000mAh LiPo battery.
The application drain a quite costant current, between 20 and 25mA, so the coulomb counter should be an easy approach for monitoring the SOC. For that reason the STC3115 has been configured with a relax current lower than 10mA.
Unfortunately the SOC estimation apparently is not reliable: during a long period discharge phase, the SOC decreases faster than expected and, moreover, below 50% it increases the descending slope. for comparison, I used the current value provided by the same component for implementing a pure coulomb counter and the behaviour is completely different, despite the original data (i.e. the current) is the same. The figure represents the two SOC estimations (STC3115 and pure coulomb counter).
Because the internal STC3115 SOC estimation algorithm is not described, I kindly ask to some expert from ST if the observed behavior make sense and/or is due to a wrong STC3115 configuration.
By the way, I calculated the battery internal resistance with the suggested approach in AN4324 (result around 1ohm), but I tried values ranging from 100mhom to 2.5ohm, without any impact on the above mentioned behavior.
Thank you in advance and best regards
