Solar Battery Charger using LM317 Simple Circuit Schematic

Eltronicschool. - There are many energy source resources that we can used to provide us electric to charge gadget's batteries easily. One of energy source is Solar that can help use to provide electric after we used solar cell to receive this energy.

In here we will show you one electronic circuit schematic for solar battery charger that using integrated circuit LM317. We think this is simple and affordable solar battery charger that electronic student and hobbyist can used and can make like in figure 1 below.

Circuit Schematic

Component List

1. C1 = 0.1
2. R1 = 220
3. R2 = 680
4. VR1 = 10K
5. D1 = 3A 50V 
6. U1 = LM317

Description  

When electronic student and hobbyist used and make this circuit schematic will get advantages and disadvantages as follow: 

1. + Simple, small & inexpensive 
2. + Uses commonly available components 
3. + Adjustable voltage 
4. + ZERO battery discharge when sun is not shining 
5. – High drop-out voltage—may be marginal for 6V application 
6. – Current limited to 1.5A 
7. – No LED indicators—no bells or whistles

According electroschematic site that publish this circuit schematic describe that Minimum Head Voltage  This is also referred to “drop-out voltage.” The input voltage must exceed the output voltage by about 2.75V @ 1.5A. Fortunately, when the battery discharged, the output voltage is lower so the solar panel voltage will also be lower.  When fully charged, the battery voltage will be high, but the current is very low—at this point, the drop-out voltage reduces to about 2V and the open circuit solar panel voltage also comes into play. The schottky rectifier was selected to reduce this head voltage requirement—the voltage drop of the schottky is about 0.5V @ 1.5A or about half that of a typical silicon rectifier.  More advanced controls have a much lower head voltage requirement and will function better under marginal conditions.

Solar battery charger specifications  

1. Solar panel rating: 20W (12V) or 10W (6V) 
2. Output voltage range: 5 to 14V (adjustable) (may be reduced further by shorting R2) 
3. Max power dissipation: 10W (includes power dissipation of D1) 
4. Typical dropout voltage: 2 to 2.75V (depending upon load current) 
5. Maximum current: 1.5A (internally limits at about 2.2A) 
6. Voltage regulation: ±100mV (due to regulation of series rectifier) 
7. Battery discharge: 0mA (this control will not discharge the battery when the sun doesn’t shine)