Off-grid solar power systems rely heavily on battery performance to maintain stable operation. However, batteries have a relatively short lifespan, are expensive, and
do not always operate at a stable voltage. Therefore, components are needed to optimize energy storage in off-grid solar power systems. Supercapacitors can be used to assist
batteries in supplying power and stabilizing voltage during load increases. By conducting simulations in Simulink Mathlab, the aim is to observe the performance of SOC, current, and voltage before and after the addition of supercapacitors with varying supercapacitor values. Supercapacitors with voltages of 2.7V and 8.1V perform poorly because they do not match the system's required voltage of 12V. At 13.2V, the supercapacitor can maintain a more stable voltage by assisting in power supply to prevent SOC degradation in the battery. As a result, the 13.5V 70F supercapacitor can demonstrate optimal performance, maintaining the system voltage at 12V and enabling faster battery charging in 22 seconds of simulation time, as required by the calculations. Meanwhile, if the power supply meets the load requirements, the supercapacitor-battery energy storage system will charge until fully charged. As a result, the State of Charge remains stable at 13.5V, and the voltage current stabilizes more quickly at 70F, which is the most optimal condition.