$4 Solar Battery Charger

Step 7: Enjoy

That was easy.  I've done this a couple of times before and at this point building one takes me under 20 minutes.

So the breakdown is this.

Cost: $4

$1 Tupperware
$2 Solar Panels
$1 Battery holder
$0.02 Blocking Diode

Time: 20 minutes.

You can use this EXACT same setup to power little light up projects.  Throw in a few transistors and resistors and you can make a dark detecting circuit for all of $0.20 more.  

If you're looking for solar panels or little solar kits I have several available on my website browndoggadgets.com.  

Comments

[tomx63]

Great instructable, Joshua!

[burdockwing]

when counting the price you didnt ad a soldering gun do you know how much those cost?

[JoshuaZimmerman]

No, but I figure that most people have such things.

You can buy one for as little as $10, but if you're going to be doing a bunch of projects like these you'll want to buy one in the more $20-30 range that has adjustable heat.

Also be sure to get one with a fine tip, not a giant tip. This makes things much much easier in the long run.

[big_F]

My local hardware/ sell it all shop sells those solar garden lights the little ones that run off 1 AAA battery, these ones have glass Solar cells and not those crappy plastic coated ones that go yellow in sunlight. Pulling them apart gives you 1 1.5v - 2.0v solar cell and 1x 800mah nimh battery. Series these little guys up and then parallel them to get some good charging voltages and capacities. All that for 87 pence each :)

[JoshuaZimmerman]

I found some solar garden lights from the $1 store here in town. The included a 3.5 volt solar cell and a 200 mah AAA battery. I bought quite a few...

You might also want to look at yard sales during the summer. Some of the nicer solar lights have rather powerful solar cells in them.

The one thing you'd need to watch out for is the power of your solar cell. A 1.5 - 2 volt cell isn't going to charge up more than one battery, and we still don't know how many amps it's putting out. To charge two AAA or AA batteries you'll need at least 4 volts of power. The more volts a cell is rated for the less sunlight you'll need to get the minimum voltage required to charge up your batteries.

Even when I'm just charging up a single AA battery I still use a 4.5 volt cell so that my battery will be able to charge for a much longer period during the day.

[Coindude19]

Awesome Instructable, I am going to make one

[ferster]

This is a great Instructable. Thanks.

I may have missed this somewhere, but do you have to make sure to STOP charging the batteries after so long? So, if I forget that there out there on my deck, can I damage the batteries?

Also, would it be hard to add a charge controller that would handle this?

[JoshuaZimmerman]

As we're only doing the "trickle" methoid we don't have to worry about over charging them. They'll max out after so long, and the trickle isn't enough to cause any extra problems.

That being said I wouldn't leave them outside for two months at a time, that would be sad.

[ferster]

Great to know. Thanks very much.