You can save on your electricitybills by switching to alternativesources of power. Thephotovoltaic module or solar paneldescribed here is capable of deliveringa power of 5 watts. At full sunlight,the solar panel outputs 16.5V.It can deliver a current of 300-350mA. Using it you can charge threetypes of batteries: lead acid, Ni-Cdand Li-ion. The lead-acid batteriesare commonly used in emergencylamps and UPS.The working of the circuit is simple.The output of the solar panel isfed via diode 1N5402 (D1), whichacts as a polarity guard and protectsthe solar panel. An ammeteris connected in series betweendiode D1 and fuse to measure thecurrent flowing during chargingof the batteries. As shown in Fig.1, we have used an analogue multimeterin 500mA range. DiodeD2 is used for protection againstreverse polarity in case of wrongconnection of the lead-acid battery.When you connect wrong polarity,the fuse will blow up.For charging a lead-acid battery,shift switch S1 to ‘on’ positionand use connector ‘A.’ Afteryou connect the battery, chargingstarts from the solar panel via diodeD1, multimeter and fuse. Note thatpulsating DC is the best for charginglead-acid batteries. If you use this cir-Fig. 1: Circuit of solar panel based chargerFig. 2: LED lamp circuitcuit for charging a lead-acid battery,replace it with a normal pulsating DCcharger once a week. Keep checkingthe water level of the leadacidbattery. Pure DC voltagenormally leads to depositionof sulphur on the plates oflead-acid batteries.For charging Ni-Cd cells,shift switches S1 and S3 to‘on’ position and use connector‘B.’ Regulator IC 7806(IC1) is wired as a constantcurrentsource and its outputis taken from the middle terminal(normally grounded).Using this circuit, a constantcurrent goes to Ni-Cd cell forcharging. A total of four 1.2Vcells are used here. ResistorR2 limits the charging current.For charging Li-ion battery(used in mobile phones), shift switchesS1 and S2 to ‘on’ position and use connector‘C.’ Regulator IC 7805 (IC2) provides5V for charging the Li-ion battery.Using this circuit, you can chargea 3.6V Li-ion cell very easily. ResistorR3 limits the charging current.Fig. 2 shows the circuit for a smallLED-based lamp. It is simple and lowcost.Six 10mm white LEDs (LED2through LED7) are used here. Justconnect them in parallel and drivedirectly by a 3.6V DC source. You canuse either pencil-type Ni-Cd batteriesor rechargeable batteries as the powersource.Assemble the circuit on a generalpurposePCB and enclose in a small box.Mount RCA socket on the front panel ofthe box and wire RCA plug with cablefor connecting the battery and LEDbasedlamp to the charger.

DOWNLOAD FULL REPORT
http://electronicsforuEFYLinux/circuit/May2009/CI-01_May09.pdf