Current estimation using Thevenin battery model

Current sensor is an important part of Battery Management System (BMS). Current information of a battery is very important to estimate the value of State of Charge (SOC) as a component of fault detection. Fault detection is very important to implement in BMS because of its function to protect battery from damage caused by over discharge and overcharge. The issue here is expensive current sensors. To overcome this issue, this research aims to design a current estimation algorithm which is based on a sensorless current method where the battery is modeled in a Thevenin equivalent circuit model. The Thevenin model is then formed into autoregressive exogenous (ARX) model and the parameters are extracted by using MATLAB identification toolbox. This research uses lithium polymer battery with a capacity of 2200 mAh and the tests conducted in this research are constant pulse load test and load variation test to see the performance of the algorithm. The results show that the current estimation using Thevenin model results better than the one using RC model as shown in the estimation test with constant pulse load and load variation.