# A Comparative Study of Storage Batteries for Electrical Energy Produced by Photovoltaic Panels
## 5 Conclusions  
This work presents a comparative analysis of a system for controlling batteries used for storing electrical energy produced by photovoltaic systems. The implementation of this system involved the development of a model in MATLAB-Simulink for controlling the loading/unloading of storage batteries with energy produced by photovoltaic panels using a buck-type DC-DC convertor controlled by means of the MPPT algorithm, which was implemented through the method of incremental conductance based on a MATLAB function. The program for the MATLAB function was developed by the author in the C++ programming environment. The MPPT algorithm provided maximal transfer of energy from the photovoltaic panels to the battery. Between the buck-type DC-DC convertor and the battery, a power electronic circuit made of IGBT-type transistors was inserted. This circuit allowed for control over battery charging and discharging. The transistors were controlled using a voltage controller and a current controller of the proportional-integrative (PI) type. In this manner, control over the voltage and current intensity was assured for the battery during its charging and discharging processes. In this study, a receptor circuit was not connected to the battery. Practically, battery discharge occurs when the solar radiation intensity is low and the photovoltaic panels cannot supply the power needed to charge the battery. During discharging, the current intensity value is positive, whilst during charging, the current value in the battery is negative. In this model, two types of batteries were successively used: Lead-Acid and Lithium-Ion batteries. The analysis of the results presented in Subchapter 3 shows that the current intensity of the Lead-Acid battery was a little higher than that of the Lithium-Ion battery. Within a time interval of 40 s, at t = 20 s, the current intensity of the Lead-Acid battery was Ib\({}_{\_}\)LA = \(-\)2.999 A, and that the Lithium-Ion battery was Ib\({}_{\_}\)Lt-I = \(-\)2.883 A. At the same time point, the voltage rate of the Lead-Acid battery was lower than that of the Lithium-Ion battery. At t = 20 s, the voltage of the Lead-Acid battery was Ub\({}_{\_}\)LA = 11.967 V, and that of the Lithium-Ion battery was Ub\({}_{\_}\)Lt-I = 12.914 V. Based on these results, it can be concluded that Lithium-Ion storage batteries exhibit higher performance than Lead-Acid storage batteries, because they are charged with a higher electric power. At the Laboratory of Electrical Machinery and Drives of the Engineering Faculty in Bacau, an experimental stand was built for a storage  
Figure 11: Variation in power factor as a function of battery voltage.  
system for electrical energy produced by photovoltaic panels. To control the buck-type DC-DC convertor, a program was developed in the programming environment Arduino IDE in order to implement the MPPT algorithm for incremental conductance. During the experimental tests, it was also observed that during battery charging, an increase in the filling factor of the PWM control signal of the DC-DC buck-type convertor took place. The findings of this study may also be applicable to electrical energy storage batteries used for supplying electrical motors in electric vehicles.  
This paper is financed by the University \"Vasile Alecsandri\" of Bacau from the funds allocated for research.  
Not applicable.  
The original contributions presented in this study are included in the article; further inquiries can be directed to the corresponding author.  
The author declares no conflicts of interest.