# Investigation of the Automatic Monitoring System of a Solar Power Plant with Flexible PV Modules
## 3 Results and Discussion
When the battery reaches a certain charge level and the voltage rises, PWM regulates the current supply by reducing the pulse duration. Pulse-width modulation causes the cycle in the \"on\" part to begin to shorten and the \"off\" part to increase. This allows for slower charging, protecting the battery from overcharging. The duty cycle can drop to 50% or less. When the battery is almost fully charged, the PWM cycles become even shorter. The duty cycle can drop to small percentages like 10% or even less. This means that only very small current pulses are sent and most of the time the charger is off. Shortening cycle means that in each cycle of the PWM pulses, the \"on\" phase, when power is supplied to the battery, is shortened and the \"off\" phase is lengthened. This allows one to effectively regulate the current and protect the battery from overcharging, especially at the end of the charging process. The results of measurements of PWM charger characteristics are presented in Figure 8  
PWM is also widely used to control LED brightness. In this case, the PWM signal regulates the brightness of the LED by alternating between \"on\" and \"off\" states in rapid pulses. A high duty cycle (close to 100%) means that the LED shines at its maximum, while a low duty cycle (e.g., 10%) provides a weaker light output. Because the signal changes rapidly, the human eye does not see the flickering, and the light appears constant. In conclusion, PWM technology is widely used not only in chargers, but also in various control systems. It allows for the efficient regulation of energy supply, avoiding unnecessary losses, while providing precise and accurate control in many areas of electronics and electromechanics [5; 6; 7]. The efficiency and speed of charging batteries depend on the efficiency of the charger and the charging process used. A comparison of PWM and MPPT charging methods where the battery voltage indicates the charge level over time is presented in Figure 2.1  
Figure 2.2 Dependence of PWM cycle length on battery charge level. As we can see from the measurement results, up to the maximum voltage of 12.8 V, the battery charges in approximately 550 min when MPPT technology is used for charging. Meanwhile, when applying the PWM charging method, the battery is charged to the mentioned voltage value in approximately 650 min. In this case, a deep discharge 40 Ah 12 V battery was used in the study. During charging, the PWM charger directly connects the output of the solar panel to the battery. The voltage can change depending on the condition of the battery, and the current is regulated by shortening the duration of the \"on\" and \"off\" signals. However, PWM cannot optimize the power point of the solar panel, so it does not always use the energy efficiently. This means that when the voltage of the solar panel is higher than the battery, the excess energy is simply lost. MPPT chargers, on the other hand, continuously monitor the output of the solar panel and optimize the charging process by determining the maximum power point. MPPT regulates the input voltage and current in such a way that it uses the solar panel's power at maximum efficiency. This allows for more energy, especially when solar conditions are unstable, such as cloud cover or temperature changes. PWM chargers work best when the solar panel voltage is close to the battery voltage. For example, if a 24 V solar panel is used to charge a 12 V battery, PWM will not be able to regulate the voltage effectively and will lose some power. Meanwhile, MPPT chargers can efficiently charge 12 V, 24 V, or 48 V batteries even at much higher solar panel voltages because they convert excess voltage into usable energy. Changes in the state of batteries during different charging modes depend on the technology used and the dynamics of the charging process. With PWM (pulse-width modulation) chargers, batteries are charged in a long and consistent manner until a certain charge level is reached.