Q: When DS2786B was used for the test of battery capacity measurement, it was found that when the power is turned on, the battery started to discharge and the battery capacity was gradually reduced. However, when it was turned on the second day, there was a difference of around 20% between the predicted capacity at that moment and the predicted capacity when it was shut down. How do I solve this problem?
A: The DS2786B is a fuel gauge based on open-circuit cell voltage (OCV) with a built-in Coulomb counter. When it is powered on, the open-circuit cell voltage will be measured once, and then the battery capacity is measured by the coulomb meter. Based on your measurement description, the cause of this problem could be:
1. The setting of internal register is incorrect. For example, the full capacity register is inconsistent with the actual battery capacity.
2. The built-in discharge curve of the device at open circuit is inconsistent with the discharge curve of the battery currently being used.
Lab experiments and tests should be run to determine the cause of this error. It should be noted that, in order to obtain accurate battery capcity reading, there has to be no load when powering on the DS2786B. In addition, if recharging the battery is required during the test process, there needs to be more than half an hour between recharges to allow the battery voltage to recover.