Figure 1. Battery storage system schematic.

Like PV cells, batteries are direct-current (DC) devices and are compatible with DC loads. Batteries not only stor e electrical energy -- in combination with a PCS, they can also enhance the quality of the power in the system. Th e battery can be discharged as required and therefore supply a variable electrical load. The PV array can then b e designed to operate closer to its optimum power output [1].

Batteries are not specifically designed for PV systems. Most of the batteries used in current small PV systems wer e actually designed for use in deep-cycle electric vehicle or recreational vehicle applications where the recharge i s carefully controlled and complete for every cycle. Insufficient battery recharge due to the diurnal limitations of P V output and poor charge control results in long periods of low state-of-charge which can be detrimental to some batteries, depending on design [2]. Lead-acid batteries are mostly used in integrated PV systems.

The PCS processes the electricity from the PV array and battery and makes it suitable for alternating-current (AC ) loads. This includes (a) adjusting current and voltage to maximize power output, (b) converting DC power to AC power, (c) matching the converted AC electricity to a utility's AC electrical network, and (d) halting current flow from the system into the grid during utility outages to safeguard utility personnel. The conversion from DC to AC powe r in the PCS is achieved by an inverter, which is a set of electronic switches that change DC voltage from the solar array and/or battery to AC voltage in order to serve an AC load [1].

The PCS also maintains the DC voltage of the integrated PV system. It protects the batteries from excessive overcharge and discharge, either of which can cause permanent damage. The PCS usually includes a solid-state device, such a s a blocking diode, that prevents current from fowing from the battery to the PV array and damaging it.

The max power tracker (also known as an auto power tracker) interfaces between the PV array and the storage system. Like the PCS, it also performs some power conditioning functions. It converts the DC energy from the PV array int o a higher DC voltage to match the existing load or storage system. The max power tracker is needed in addition to the PCS to handle the voltage variability of the PV array and maximize its power output. The max power tracker monitors DC amperage and voltage from the PV array and employs an iterative method to match DC voltage of the PV arra y and the battery.

The key differences between the max power tracker and the PCS are:

DIY Battery Repair

DIY Battery Repair

You can now recondition your old batteries at home and bring them back to 100 percent of their working condition. This guide will enable you to revive All NiCd batteries regardless of brand and battery volt. It will give you the required information on how to re-energize and revive your NiCd batteries through the RVD process, charging method and charging guidelines.

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