ABSTRACT

        This project work describes the construction and designing of 12volt car battery charger with USB port for charging mobile phones. The charging process is focus more on 12volt lead car batteries commonly used in vehicles. This design was done by using I.C LM7812 and LM7806 with transformer of 230 volt and series of other electrical component highlighted in the work to achieve our goal. The charger was able to charge lead car batteries within the maximum of 70mAh faster and with a feasible port charging usb enable cell phones, The design also has LED indicators which determine the battery level when fully charged or a completed down battery.

Unlike any other battery charger, this project is about the combination of battery charger circuit with usb charging circuit. The charging process is halt manually by turning of the circuit to displayed full 3LED light as fully charged battery. The theory, design, circuit analysis, and circuit diagram were provided to give adequate information about the design. 

CHAPTER ONE

                          INTRODUCTION AND LITERATURE REVIEW

1.1      BACKGROUND TO THE STUDY

In our society today writing a project is all about applying the theories learnt over the year to produce design and construct and operating system which will be capable of performing a known task.

It is from this point of view that we decided to write, design and construct this particular project which has the titles construction of 12volt battery charger with usb port using LM7812 and LM7806 used in controlling the current flow in the circuit system.    

A battery charger is a device used to put energy into a cell or (rechargeable) battery by forcing an electric current through it. Lead-acid battery chargers typically have two tasks to accomplish. The first is to restore capacity, often as quickly as practical. The second is to maintain capacity by compensating for self discharge. In both instances optimum operation requires accurate sensing of battery voltage.

When a typical lead-acid cell is charged, lead sulphate is converted to lead on the battery’s negative plate and lead dioxide on the positive plate. Over-charge reactions begin when the majority of lead sulphate has been converted, typically resulting in the generation of hydrogen and oxygen gas. At moderate charge rates, most of the hydrogen and oxygen will recombine in sealed batteries. In unsealed batteries however, dehydration will occur.

The onset of over-charge can be detected by monitoring battery voltage. The figure.1.1 on the next page shows battery voltage verses percent of previous discharge capacity returned at various charge rates. Over charge reactions are indicated by the sharp rise in cell voltage. The point at which over-charge reactions begin is dependent on charge rate, and as charge rate is increased, the percentage of returned capacity at the onset of over-charge diminishes. For overcharge to coincide with 100% return of capacity, the charge rate must typically be less than C/100 (1/100 amps of its amp- hour. 

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