Two main challenges are encountered in photovoltaic (PV) based battery chargers, namely, the variable input power and the fluctuating temperature. As a result, traditional charging techniques that rely only on the terminal measurements such as the current, voltage or temperature are not reliable in those chargers. Furthermore, relying only on the terminal measurements without other indirect measurements can result in terminating the char. Two main challenges are encountered in photovoltaic (PV) based battery chargers, namely, the variable input power and the fluctuating temperature. As a result, traditional charging techniques that rely only on the terminal measurements such as the current, voltage or temperature are not reliable in those chargers. Furthermore, relying only on the terminal measurements without other indirect measurements can result in terminating the charge before the battery is truly fully charged, which has several drawbacks such as reducing the usable capacity and possibly leading to memory effect in nickel-based batteries, or overcharging the battery which can lead the battery to prematurely reaching its end-of-service. This paper presents design considerations and evaluates the performance of PV chargers used to charge major battery chemistries including nickel–cadmium (NiCd), nickel-metal-hydride (NiMH), lithium-ion (Li-ion) and sealed lead-acid batteries at real operating conditions.••••Review of design requirements for outdoor PV battery chargers for major batteries.••Evaluation of charging techniques for traditional and PV chargers.••Improving coulomb counting SOC estimation technique by estimating the initial SOC.••Evaluating the effect of ambient temperature on the charger's reliability.BatteryChargerPhotovoltaic (PV)State-of-charge (SOC)Renewable energy technologies have been gaining great attention recently due to environmental issues such as the continuously increasing levels of CO2 emissions as well as strategic economic issues related to expected lack of fossil fuel. As a result, many countries around the globe have taken actions to increase the amount of power generated by renewable sources. As an example, in UAE, the average solar radiation year round has one of the highest values in the world. In order to diverse the energy resources in UAE, which is among the highest priorities in the country, UAE has legislated many new policies recently to encourage the use of renewable energy sources such as solar power. Abu Dhabi's Economic Vision −2030 aims at generating 7% of Abu Dhabi energy requirements from renewable resources. In Dubai, it is projected to generate 1% of electricity needs from renewable sources by 2020 and 5% by 2030.As a result of the intermittent nature of PV power, PV systems are usually backed up with batteries in order to minimize the fluctuations in the generated power. However, batteries are expensive and are the least reliable part of a renewable energy system. In addition, batteries usually reach their end-of-service life prematurely adding more concerns to their reliability and feasibility. The battery quality gets even worse when exposed to high outdoor temperatur. The PV output power varies with sun irradiance and ambient temperature. Hence, DC–DC converter is added to regulate the output voltage and to control the PV system operating point around the maximum power point (MPP). Fig. 2 shows a simplified PV battery charging system.To optimize the design of the power conversion stage, many aspects must be considered. These aspects are application dependent. One main aspect that must be addressed in any PV system in general is the grounding requirement. Ungrounded PV systems provide the best fire hazard reduction, where grounded PV systems provide the best personnel protection from electrical shock, according to. Generally, for systems with relatively high voltages, grounding is substantial for safety, electromagnetic coupling suppression, and electromagnetic pulse protection (EMP). In the U.S., all electrical systems with voltages greater than 50 V must be grounded. Grounding is achieved by either connecting the PV source itself to the ground and monitoring for ground faults, or by connecting all components including the PV source, power converter and metallic chassis to the ground.Another important issue is the galvanic isolation in the DC conversion stage. Transformers are commonly used in power converters since they provide galv.
