Travel AA Solar Charger - Altoids!

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

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

Tools:
Soldering Iron

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

*** Several people asked me to put together a kit of all the parts with a discount, so here is that kit.

Comments

[SeedRally]

Instead of using the blocking diode, do you think it would be just as efficient to use an LED and a resistor? That way we could visible see if there is enough voltage going through the circuit?

[snailofsatan]

excuse me for my ignorance, but is this the correct type of diode?

100V 200mA High Conductance Fast Diode:
http://uk.rs-online.com/web/p/rectifier/7044013/

[frogier]

Hi, is there a way this could work as a charger for a Macbook??

[JoshuaZimmerman]

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.

[solarstudent]

If we wanted to decrease the time it takes to charge our batteries, would be be better off increasing the voltage or current output of our solar cells?

[JoshuaZimmerman]

Current. Current charged up the amps, you just need a certain minimum level of voltage to get the batteries to charge.

So adding a second 4V solar cell you could either get 8V 60mA or 4V 120mA.

To charge in lower light, you'd want to go for 8V 60mA.

To charge up the batteries faster, you want 4V 120mA.

[Prof.Jon]

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?

[JoshuaZimmerman]

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.

[solarstudent]

If I wanted to use this design to charge 4 batteries is it as easy as doubling all the requirements?
i.e. need at least 7V

also, with the 10% of battery capacity rule: is it only 10% of one battery, or 10% of the sum of the batteries current capacities.
i.e. 10% 1 battery @2000 mah = 200 mah
10% 4 batteries @2000 mah = 800 mah or is it still 200 mah?

Your Instructables are amazing! keep up the good work!

[JoshuaZimmerman]

10% of the capacity of the battery system.

How you wire them up determines their capacity.

Hook them up in Parallel and you keep adding capacity. 1 AA is 2,000mA. 2 AA in Parallel is 4,000mA. 3 AA in Parallel is 6,000mA.

[Citymanins]

What about useability of the mobily charger? What time is it need for full charging of a phone?

[scottinnh]

As the author says, but 1 more comment:

use this to charge your AA's...
... then use your AA's - with a MintyBoost circuit - to charge your iPhone.
As long as you get your AA's charged, this -will- work.

[JoshuaZimmerman]

It's a battery charger, not a phone charger. Just AA and AAA batteries.

Depending on how low your batteries are it can take anywhere from 5 - 10 hours of sunlight. The way I use it is that I have a spare set of batteries stored in the tin, then swap out my "dead" batteries with those spare and then charge the "dead" ones up. By the time my spares are used up my "dead" are all charged.

[nida22]

hi i have an idea if you just use the regulator and then simply connect the battery

[JoshuaZimmerman]

The design honestly can't get more simple than this. Trust me.

[javajunkie1976]

What about larger batteries such as the batt packs for power tools? I work on a Halloween layout set in the backwoods area where it's kind of difficult to run power.

[JoshuaZimmerman]

That depends on the type of battery. Lithium Iron Batteries need "smart" controllers to charge them up. Ni-Cad and NiMh batteries don't, as long as you trickle charge them.

You could always build a 6V power system using a 9V Solar Panel (say around 3 watt)_, a cheap charge controller, and a big 6V battery.

[edsilvestre]

what are the elements in making solar cell so i can make my own?

[JoshuaZimmerman]

Look around instructables, I know I saw someone showing how to make your own solar cells.

Though if you want to use them in projects I would suggest not doing so. The ones you make are going to be very very poor compared to even the cheapest factory made ones. Shoot, you can get them for free if you can find someone throwing out old garden lights.

Though I've seen quite a few places selling new solar graden lights for less than $3, which is darned cheap for a solar cell + LED + circuit + rechargeable battery. You might as well buy one and gut it.

[jeffreyshi]

Could you charge a Nintendo 3DS with this?

[JoshuaZimmerman]

The 3DS doesn't run on AA batteries, so no. What you could use is a AA to USB converter. Like what I use with my Altoids Solar USB Charger.  I also have a kit for that as well if you'd rather build it yourself.

Then you'd just need a USB cable to hook into your 3DS.  I've seen them before, so I know you can find them.

[jeffreyshi]

thanks. I'll go buy the USB Charger kit.

[JamFish]

Love so far what I've read. However, I'm just curious....type of solar panel would I need to charge a smartphone? Like a Nexus S?

[JoshuaZimmerman]

USB runs on 5V of power, so you'd need something bigger than 5V and then use a 5V regulator to keep it at 5V. Always go bigger with solar, so that even in lower light conditions you're getting your minimum voltage.

Or you can use a voltage booster which would take a low voltage and boost it up to the 5 you need. If you're interested I have such a kit available on my website, and I'm going to be writing an instructable on it quite soon.

The kit to make the circuit.

A solar to USB system built into an Altoids tin.

[d.i.y master]

this is great i have been looking for something like this forever but they are usally to complicated or to pricey. great instructable

[JoshuaZimmerman]

Building your own solar trickle charger is really easy to do. It's a great project for anyone getting into electrical circuits or solar power. Plus it's darned useful.

[young skipper]

Man I've been waiting for this. I think... I think I love you.

[JoshuaZimmerman]

Nice.

[young skipper]

It's a beautiful relationship we have.

[JoshuaZimmerman]

Very minty fresh it is.

[EngineeringShock]

Awesome job! Those are some nice solar cells =)
Where do you keep finding these altoid cans???

[JoshuaZimmerman]

I'd hate to give up my supplier.... but to be honest I just order them off ebay. You can buy them for about $0.90 a tin. I recently bought 50 from a guy, and several months back I bout 180 Altoids gum tins (at 30 cents a tin).

Otherwise if you like mints it wouldn't be too hard to buy one every now and then and enjoy yourself.