Solar Battery Charger

Why buy a battery charger when you can make a solar powered one?

Things you’ll need:

• Solar panel (I used a 3V / 250mA one)
• Used up rechargeable batteries (I used 1 AA and 1AAA)
• Mint tin (I’ll be using a herbal candy tin)
• Some wires
• 1 AA battery box x 1
• 1 AAA battery box x 1
• 1N4148 diode
• 2.5mm female plug
• 2.5mm male plug
• Electrical tape
• Hot glue
• Soldering iron
• Solder

!! Attention !!

For safe charging, make sure that the rating of the solar panel (250mA) is less than 10% of the capacity of the battery setup (AA – 1900mAh, AAA – 800mAh, hooked up in parallel gives me 1900+800 = 2700mAh, 2700 x 10% = 270 > 250, so that’s fine). However, I’ve tried inserting 1 AAA only to the circuit (800 x 10% = 80, way lower than the rating of the solar panel), nothing bad happened – just be warned that you can overcharge your battery in this way.

Solder the positive wire to the longer leg of the 2.5mm male jack and the negative wire on the other. Then connect the wires to the solar panel.

Solder the postive wires of the battery packs together. Repeat for the negative wires.

Place the plug with the empty side facing down. The left tab is negative and the middle one is positive.

Solder the negative wires to the left tab, and the 1N4148 diode to the middle tab. Remember that the black side of the diode should be facing away from the tab. Hook it up to the positive wires.

Drill a hole for the female plug

Insulate the tin with some electrical tape. You can also wrap the soldered part of the wires with some tape.

Hot-glue the battery pack to the tin