Instructables

$4 Solar Battery Charger

Featured

Step 7: Enjoy

Picture of 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.  
 
Remove these adsRemove these ads by Signing Up
mpeterson197 months ago
Could a charge controller be placed somewhere between the solar panels and the batteries? And can the batteries be charged while they are also powering a small device?
Great Instructable.

Just wondering how much the voltage of the solar cells matters? You went into depth about the amps, but only mentioned that your cells run at 4v.
Does the voltage need to be higher than the battery supply?

Also what happens if you do leave them to charge for months? I have some ideas for projects, but they would be sitting outside for a long time...
tomx632 years ago
Great instructable, Joshua!
burdockwing3 years ago
when counting the price you didnt ad a soldering gun do you know how much those cost?
JoshuaZimmerman (author)  burdockwing3 years ago
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_F3 years ago
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 :)
Coindude193 years ago
Awesome Instructable, I am going to make one
ferster3 years ago
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 (author)  ferster3 years ago
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.
Great to know. Thanks very much.