Travel AA Solar Charger - Altoids!




About: I used to teach middle school science, but now I run my own online educational science website. I spend my days designing new projects for students and Makers to put together.

I do a lot of camping in the summer and like to travel light. I also love taking photos and hate it when my batteries die right before I take an awesome photo.

Thus I decided to design a little battery recharger that was small, light weight, and cute. Ok, the cute part wasn't the original idea but who can argue with cute?

Cost: $5
Time: 20 Minutes
Difficulty: Very Easy

Step 1: What You Need

4V or greater solar cell
AA or AAA battery holder
1N914 Blocking Diode
Altoids Tin to house it in (or whatever)

Soldering Iron

All the supplies for this project can be found at my website, BrownDogGadgets. 90% of the money goes to me making more projects, the other 10% goes for dog treats and the occasional stuffed frog toy.

Step 2: Cells and Charging

Almost all rechargeable batteries you buy in the store are NiMh batteries. Usually people use a wall adapter to quick charge them in an hour or so, but we're not going to be that fancy. We're going to use the "trickle" method to slowly charge them up over time. This also prevents them from overcharging or getting destroyed.

To be safe we need to be sure that we're not throwing more than 10% of their capacity at them when charging. For example my AA batteries have a capacity of 2,000 mah. The max I can charge them at is 200 ma.

When you decide what solar cell to use make sure you're not going over the 10%.

At the same time be sure that you're getting at least 3.5 volts out of your solar cell otherwise the batteries won't charge. Remember, the more voltage your cells put out the less sunlight you'll need to reach your minimum voltage requirement. (Higher voltage cells = more charge time, even in low light.)

For this project I've chosen some 4V cells that put out 50 ma. I picked it because it's just the right size to fit into the Aloids tin. If you pick a bigger sized cell you can always glue it onto the outside of the tin.

You could also use a combination of smaller cells. I've used combinations of little 1.5V and 2V cells in series to get my desired voltage levels, while still fitting inside the tin.

Step 3: Hook Up the Diode

We need a blocking diode. This prevents the solar cell from sucking power out of the batteries when in darkness.

The 1N914 is a good diode as it has a very low voltage drop and is very common.

You want to connect the red wire from your battery holder to the black bar leg of the diode.


Otherwise you won't get any power from the solar cells.

Step 4: Solder the Solar Cell

Now heat up your soldering iron.

Solder the other leg of your diode to the positive solar point.

Solder the black wire from your battery pack to the negative point on your solar panel.

Don't forget to solder the red wire to the diode.

Snip off the extra bits of the diode.

Lastly you can use some tape to keep it all together. Hot glue/ melt glue also works. We'd hate to rip out the wires by mistake.

Step 5: The Battery Pack

I find it helpful to snip off the tops of the battery holders. All the ones you find in stores have these horrible plastic "guards" on them. they're great at keeping batteries in, and a pain to get batteries out. As we're wanting to do a lot of battery switching, removing them isn't a bad idea.

I like to use double sided foam tape to keep my battery packs down. You can use hot glue/ melt glue if you want. Heck you might not even need to use anything as the battery pack is nearly a perfect fit inside the tin.

Well just put it in and see how it works.

Step 6: Enjoy

And that is it. We're done. The best part is that the solar cell fits perfectly inside the tin so we can shut the top. No one would ever know that we've got a solar charger inside.

If you really wanted to be crazy you could put a little charge indicator light in there, or a test LED.

I hope you found this helpful. These are easy to make and are also really fun to give away as gifts, especially to people who are always on the road.

If you'd like parts or a fully made charger you can grab one at my website BrownDogGadgets.

***Several people asked me to put together a kit with a bit of a discount, so here is that kit!



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53 Discussions


3 years ago

Hi Josh I am needing some help with something... I have a small set of lights powered by a 2aa battery pack... I want to throw a solar charger into the process. How do I connect a charger to them. Or easier question, how would I hook a set of AA powered lights to the battery pack.


3 years ago

Hi josh. I have a switch in my battery charger do I turn it on to charge it or off to charge it?


3 years ago

I have a 5v solar panal. Should i use the same diode described above or is there any other i should go far ??


3 years ago

so my issue was trying to also attach a crank charger to the battery unit provided in my kit.
the question is: Is it possible to just splice in a secondary power source into the battery compartment, or would I need a resistor for that?
oh I bought your 3d printed case kit.


4 years ago on Introduction

Hi Josh,

I am a beginner in electronics and for my school project I am making this really cool Altoids Solar Charger based off the instructable. The whole reason I am doing it is to make it based off a schematic. Is there any way you have a schematic for this project because I really need one, so I can order the kit and make it. Get back to me as soon as possible.


1 reply

Reply 4 years ago on Introduction

Forgot to add that in the schematic that is it possible to add a usb port to charge phones?


Reply 4 years ago on Introduction

You could charge a chromebook, though, I believe those are 5v. You would need a long time and lots of batteries, though.


You'd need a lot more voltage and amperage for that to happen.

That's a "big scale" solar project, unlike this small scale solar project.


6 years ago on Introduction

I am not very good with circuits, as I don't know much at all about it, but could you just make 2 parallel circuits, one for AA, and one for AAA, hook both of them to the same panel, and have a switch to go from charging your AA to your AAA instantly?
I would do this, but I haven't gotten my solar panel collection yet.

1 reply

Reply 4 years ago on Introduction

Yes, you could. A couple of things to keep in mind:

The AAA batteries AND AA batteries must be the same voltage, and both rechargeable. The switch should be a three way toggle.

Here's a schematic:

Solar Schematic.jpg

Reply 4 years ago

put a switch between solar panel +, and battery + that will cut the solar panel from the battery

I have made on of these kits but when I plug my phone in, the battery from my phone drains instead of charging the phone. Any help would be nice. THank you


5 years ago on Step 6

Is there a simple way to install an LED so I can know if the battery is charged? I'm sure there is, but not sure how! Any suggestions? Love the AA charger in the sealable tupperware box! Works great!


7 years ago on Introduction

I got your kit in the mail today and I'll be soldering it up this weekend. I just read through the instructable and at the end you have that aside about getting crazy and adding a charge indicator or test light. I'm new to electronics. How would I go about doing that?

2 replies

Add an LED into the mix so that it's parallel with the solar cell, but also wire a button in so that the LED isn't always on. Use a blue LED which requires 3.6V power. As your batteries can't power it it would have to run off the solar cell.

Push the button and see if there is enough power coming in.

I'm sure there is a better way, like using some sort of voltage trigger, but I like keeping things very uncomplicated.