Analysis and implementation of an adaptative PV based battery floating charger Nabil Karami a,⇑ , Nazih Moubayed b , Rachid Outbib a a Laboratory of Sciences in Information and Systems (LSIS), Aix-Marseille University, Marseille, France b Department of Electrical and Electronics, Faculty of Engineering 1, Lebanese University, Tripoli, Lebanon Received 3 August 2011; received in revised form 9 March 2012; accepted 7 May 2012 Available online 6 June 2012 Communicated by: Associate Editor Elias Stefanakos Abstract In a system composed of a photovoltaic (PV) cell, a converter and a resistive load, the Maximum Power Point Tracking (MPPT) techniques are applied at the output of the PV panel and not at the level of the load. In this study, the considered load is a battery at different States Of Charge (SOC) that is charged by the PV panel. The power consumed by the battery is related to its SOC. Conse- quently, an empty battery consumes more current than a charged one. At full state of charge, the battery does not call for more energy and thus it is not rewarding to extract more power from the PV panel. Besides, in a stand-alone photovoltaic system, the size of the PV panel and the battery should be respected. Thus, the PV current at different irradiances should be compatible with the charging current required to charge the battery at different SOC. A critical situation occurs at high irradiance when the PV panel delivers a high current at Maximum Power Point (MPP) that exceeds the tolerated charging current. The current reaches the top limit when the battery is totally empty, caused by the big difference in potential between the con- verter output and the battery voltages. In this case, the battery starts to gas when attempts are made to charge it faster than it can absorb the energy. On the other hand, in a fully charged battery, the difference in potential between the converter and the battery is zero. In this case, there is no need to track the MPP. In this study, we will focus on the load type and suggest new methods to reach the MPP depending on the load state. In the proposed designs, the components of the stand-alone system are protected even if they are not well sized. In addition, we will focus on the devel- opment of the PV array mathematical model. The results achieved with the system, as well as the experimental results of a laboratory prototype, will be given. Ó 2012 Elsevier Ltd. All rights reserved. Keywords: Renewable energy; Solar panel; Photovoltaic cell; Battery; DC/DC converter; MPPT 1. Introduction Photovoltaic energy has become one of the most prom- ising sources of energy as it is a free and sustainable energy. A PV array under constant uniform irradiance has a cur- rent–voltage characteristic (I–V curve), as shown in Fig. 1. There is a unique point on the curve, called the max- imum power point, at which the array operates with max- imum efficiency and produces maximum output power (Tan et al., 1991; Hohm and Ropp, 2000). When a PV array is directly connected to a load – ‘direct-coupled sys- tem’ (Fig. 2a), the system operating point is at the intersec- tion of the I–V curve of the PV array and the load line. In general, this operating point is not at the PV array’s MPP, which is clearly seen in Fig. 1. That is, the MPP of the PV generator is reached only in some moments throughout the year. Thus, it is possible to talk about lost PV generator utilization, therefore, in a direct-coupled system, the PV 0038-092X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.solener.2012.05.009 ⇑ Corresponding author. E-mail addresses: nabil.karami@lsis.org (N. Karami), nmoubayed@ ieee.org (N. Moubayed), rachid.outbib@lsis.org (R. Outbib). www.elsevier.com/locate/solener Available online at www.sciencedirect.com Solar Energy 86 (2012) 2383–2396