State of Charge (SOC) Estimation on Lead-Acid Batteries Using the Coulomb Counting Method

Batteries are an important component in the implementation of renewable energy. One type of battery that is often used in the implementation of renewable energy is lead-acid batteries. Accurate estimation of the SOC (state of charge) value is one of the important parameters in the design of a BMS (Battery Management System). Accurate determination of the estimation of the SOC value is necessary to avoid the battery operating in an over charge and over discharge state. One method of estimating SOC that is quite easy and often used is Coulomb Counting. The determination of SOC estimation by this method is carried out by adding up the incoming charge or the charge coming out of the battery within a certain period of time. Charge summation can be done by summing the current in the battery, both at the time of charging and discharge. In this research, SOC monitoring tool was designed using the coulomb counting method to monitor the SOC value of the battery both at the time of charging and discharge. In its implementation, this method is very dependent on the accurate initial SOC value and the accuracy of the current sensor used. The type of current sensor used in this SOC monitoring tool is ACS712 which has good accuracy. Based on the results of the tests carried out, the amount of charge on the battery is directly proportional to the SOC on the battery itself.