We ‘ll show you how to make your own awesome solar battery charger from very simple & cheap components. You ‘ll be capable of sourcing the exact components yourself.
Step 1: The Components Required
The Copper-Stripboard includes copper tracks rows. Each & every track is electrically separated from its adjacent components. It has holes for components.
The Battery Holder … holds your batteries…. & comes into play with two pins, one for the +ve & one for the -ve ends, they’ll be soldered into the strip-board.
100 Ohm resistor – at a point this was necessary in the kit as the LED couldn’t cope with some of voltages in the experiments-however, the new LEDs do this & the resistor is simply in there because it is advertised as such! Maybe you ‘ll be needing it when you ‘ll expand your system.
LED – this is the high-intensity light emitting diode. 3.2-3.6V forward voltage, with 10000 mcd at 20 ma. A LED must be kept in the circuit the correct way around. The longer leg should receive current from the +ve terminal/direction.
1N5817 DIODE – this diode lets the current flow in only one direction-this blocks battery’s power, discharging through the solar panel at night. The system will drops 0.2V. This blocking diode also requires to be placed in the circuit in a correct orientation. The diode constitutes a circular band across its barrel at one end of the diode. This must be very close to the -ve/ground.
Wires -Usually included at least 4 wires-a black & red wire for the solar panel, a brown wire used as a jumper & another wire for use in un-soldered testing.
Solar Panel – The back of the solar panel is shown in image. On the solar panel in center of left-side & right-side you ‘ll see a very small panel of smooth meta-this is the -ve/+ve terminals. I have marked the +ve side by adding black small dots on that side. This solar panel ‘ll give an output of max of 3V at 150ma.
HINT – you should possibly purchase a multi-meter & know how to use it-this ‘ll tell you important information about typical voltages & currents your solar panel ‘ll produce in variable weather situations.
Step 2: The Solar Panel – attaching wires
Attaching the black & red wires to solar panel
For attaching the wire, one can make use of the soldered or the un-soldered method. Soldered is the pretty best method to go with & I ‘ll show you snapshots of both – if you like using more panels or using the single panel a lot you ‘ll find it best to mount the panel onto a piece of sheet wood or plastic. This ‘ll keep the wire in its place & block strain on the contacts, plus wires.
You can find an example of the solder-less method…. Yes that is cellotape! The red squares show where the contacts are. The wire ends were stripped, flattened onto the contacts & firmly taped in place. I don’t suggest using glue! – you won’t get the wire staying in touch with the contacts because the glue gets in the way. Allow some tape to move round the solar side to ensure a firm placement.
Also shown is the soldered method. Not the most fantastic job in the world but it is held securely. Always make sure that contact points are free from grease & clean.
Step 3: Main Experiment
Place a rechargeable fully charged 1.2V Nimh battery into battery holder-I assume you know the right way round to insert it. The 1.2V battery on its own ‘ll not be strong enough to enlighten the LED. The 2-3V solar panel ‘ll also carry a lot of problems while lighting the LED by itself. We can try to use the battery’s voltage plus the voltage of solar panel to operate the LED.
Connect the NEGATIVE leg of the battery holder to RED POSITIVE terminal of the solar panel. Use some more wire supplied to connect the +ve end of the battery holder to any longer of the two legs of the LED. The longer leg of an LED is always interfaced with the +ve side of the circuit. Then connect the -ve wire of the solar panel to the other LED leg. If the battery is fully charged & you have a sunny day the LED should light up. You can even power the solar panel from a powerful torch or lamp by shining it onto the panel. Try the experiment by attempting to enlighten the LED with the battery alone, or with the solar panel only.
Step 4: Charging Your Battery – Part 1A
And now we come to making your own battery charger.
The solar cells’ +ve terminal is interfaced through the diode to the +ve terminal of the 1.2V battery. If the voltage of the solar cell drops below 1.4 volts & with the 0.2V the blocking diode takes there won’t be enough potential to charge the 1.2V battery. The main purpose of the diode is to avoid current dissipation from the battery to the solar cell when this low voltage situation occurs in the solar cell.
Step 5: Charging Your Battery – Part 1B
The next photo shows the front of the completed & soldered circuit.
The red lines at drawn the bottom show you how the copper tracks are aligned on the other side of the board. The blue lines show you how the circuit completes through its electrical common points ( e.g. the tracks ). See how the small silver band at the top of the diode is towards the +ve terminal of the battery. It permits to flow towards the battery but not from it.
It is possible to go through the brown wire & connect the black/-ve wire the same track as the -ve end of the battery. We simply wanted to show a more ‘closed’ circuit form.
Step 6: Charging Your Battery – Part 1C
From below you can see the soldered connections & how they run along the copper tracks. I have added in the brown wire as brown line & the diode as a blue line, I have also added in the +ve & -ve makers for the battery. Remember that the position is flipped from the previous photo.
Step 7: SOLAR BATTERY CHARGING FACTS
The maximum output of the solar cell is 150 mA. This is with the best conditions. A high capacity rechargeable Nimh can hold 2000mAH. This means that it will take ( 2000/150 ) hrs to fully charge it. This is about 13hrs approx!
When choosing solar cell arrangements one needs to work out that
a) How many batteries do you have to charge at once
b) How fast do you want them to charge.
By adding extra solar panels one can charge more batteries & can charge batteries faster or even both at the same time.
So how does this work?
Step 8: I want more voltage!
In order to double the voltage you need to join two solar panels in series. i.e. you need to connect the -ve terminal of one solar panel to a +ve terminal of the other solar panel. This ‘ll then leave you with a +ve terminal from one panel & a -ve terminal from the other to connect your wires to. In this case you would then have a solar panel rated to a maximum of 6V at 150ma ( the maximum voltage of a single panel is 3V ). More voltage would allow to charge more batteries at the same time – just remember that although 3V is the maximum rating of the solar panel, you need to get an idea of the typical output for your climate. The batteries would also need to be connected in series ( -ve to +ve like in most multi-battery devices ). The circuit diagram shows below the solar cells in series & their accumulative voltage.