In this post we discuss elaborately an automatic solar charger circuit using a single transistor relay circuit.
Simple Charger using a Battery and Solar panel
A solar panel can certainly be applied to directly charge a battery with virtually no other elements. Just hook up the panel with the battery and it can charge once the panel begins getting dazzling sunshine - offering the panel a voltage of minimum 30% to 50% more than battery power you might be charging.
Below is a few remarkable information:
The voltage from the solar panel is not important and the voltage of the battery really does not make a difference. You are able to hook up any solar panel to any battery - ensuring the solar panel constitutes a voltage minimum 30% to 50% higher than the battery you might be charging.
The output voltage of the solar panel may only adjust to the voltage from the battery. Despite the fact that there exists a voltage mis-match, there isn't any "missing" or thrown away energy.
A good 18v solar panel "runs into" a 12v battery using the optimum current it could possibly generate once the strength of the sunlight is a highest.
To avoid an excessive amount of mis-match, it is strongly recommended you keep the panel voltage to inside 150% of the battery voltage. (6v battery - 9v utmost solar panel, 12v battery - 18v optimum panel, 24v battery - 36v spork panel).
However below is the key factor: In order to avoid overcharging of the battery, the wattage of the solar panel is extremely important.
When the wattage of your 18v panel is 10watts, the current is 10/18 = 0.55 amps = 550mA.
To counteract overcharging a battery pack, the charging current must not be greater than one-tenth its amp-hr capacity.
In particular, a 2,000mAhr group of cells must not be charged at a level beyond 200mA for 14 hours. This can be referred to as its 14-hour rate.
Yet this rating can be a CONSTANT RATING as a solar panel delivers an output for approximately 8 hours each day, you are able to boost the charging current to 550mA for Eight hours. This may provide the power to completely charge the cells.
For this reason a 10 watt solar panel could be directly attached to a group of (practically fully discharged) 2,000mAhr cells.
For a 12v 1.2AHr battery, the charging current is going to be 100mA for 12 hours or 330mA for 4 hours along with a regulator circuit is going to be necessary to protect against overcharging.
For any 12v 4.5AHr battery, the charging current is going to be 375mA for Half of the day and a bigger solar panel is going to be necessary.
The Role of a Blocking Diode
Some solar panels may discharge the battery (a touch) while it isn't obtaining sunlight and a diode is usually included with to protect against self discharge.
This diode lowers 0.6v once the panel is working and can cut down the ideal current (somewhat) while the solar panel is charging the battery. In case the diode is Schottky, the voltage-drop can be 0.35v.
Some solar panels incorporate this diode - known as BYPASS DIODE.
How to Stop Overcharging
You will find a couple of methods to protect against overcharging the battery.
1. Discharge the battery practically thoroughly every night and make use of a solar panel which will mainly offer 120% of the amp-hour capacity of the battery the next day.
2. Put in a VOLTAGE REGULATOR.
Here is the most basic and least expensive regulator to charge a 12v battery.
The solar panel should have the ability to generate a minimum of 16v on NO LOAD. (25-28 cells). The diagram simply exhibits a 24 cell solar panel - it ought to be 28 cells.
The one other factor you need to think about is the wattage of the solar panel. This can count on how quickly you would like to charge the battery and/or just how much power you take out through the battery every day and/or the amp-Hr capacity from the battery.
As an example, a 12v 1.2A-Hr battery consists of 14watt-hours of electricity. An 6watt panel (16v to 18v) may give you 18watt-hours (in glowing sunshine) in Three hours. The battery will probably be totally charged in 3 hours.