Calculation of SOC measurement in Self Discharge mode

[thailivenkatesh8]

Dear Sir,
              Using MC33771C BCC driver calculated SOC using coulomb count method. For fully charged battery SOC is 100%.When the controller is in sleep mode(STOP1 power mode)that time we have self discharge & AH decrease in battery pack. But my battery pack showing 100% even if self discharge for long time how to correct this decreased Ah to SOC & estimate the proper SOC.

Thanks & Regards,

Venkatesh

[PhilippePerruchoud-NXP]

Hello Venkatesh,

If your battery pack is not used for a long time, I would recommend to recalibrate the SOC by performing an open circuit voltage (OCV) measurement before the battery is used again. This will give you a pretty accurate indication of the battery SOC.

The self discharge could also be estimated provided your MCU has a RTC and is able to compute how long the battery has been in idle mode. If you have a modeling of the discharge over time of your battery, you can easily compute the self discharge of the idle time. But I would rely better on the first method because self-discharge is quite temperature dependant and temperature is a parameter that you won't have in the second method.

Best regards,

Philippe