How to make a solar iPod/iPhone charger -aka MightyMintyBoost

Step 1 Tools and materials

Here's what you'll need to build your own MightyMintyBoost:

Tools:
Soldering iron
Scissors
Wire cutters
Pliers (or muiltitool)
Multimeter
Metal shears
Clear packing tape

Materials:
MintyBoost kit
Lithium polymer battery charger (the original one specified was discontinued)
3.7v 2000mAh Lithium Polymer battery
JST connector/wire
Small solar cell
2" x 3" adhesive backed Velcro
Small double sided adhesive squares
Altoids tin

7/10/10 UPDATE: Adafruit now also sells all the parts you need to make this a bit more mighty. Have a look here!
http://www.adafruit.com/blog/2010/07/09/how-to-make-a-solar-mintyboost-a-solar-power-charger-for-your-gadgets/

7/18/11- ANOTHER UPDATE: Adafruit recently introduced a new LiPo charger that is specifically designed for solar charging that has much better performance. It's not as small but the performance gains would make it worth it. Have a look and read about the design here-
https://www.adafruit.com/products/390


Some notes:

The single cell Lithium Polymer charger can accept input power that ranges from 3.7 to 7v maximum. When the cell reaches full charge the charger will automatically switch to trickle charging. When charging using the mini USB port, the charging current is limited to 100mA. When charging using the barrel plug jack, the charging current is limited to 280mA.

The solar cell maxes out at approximately 5v @ 100mA in bright sunlight. If you need faster charging simply use a larger solar cell- a 6v cell @ 250mA would work very well and they are easily obtainable and inexpensive. I used the size of solar cell that I did because I wanted it to be super compact.

I could not find out from the manufacturer if the solar cell I used has a blocking diode. A blocking diode is used in many solar charging systems to prevent the solar cell from draining the battery during low light conditions. Instructables member RBecho pointed out that the charging circuit used negates the need for a blocking diode in this application. You can tell when the solar cell is producing enough power because the little red LED on the charger will come on during charging.

Comments

[stukz]

what is the total coast of all the parts?

[Honus]

Look in the FAQ section- it's all there.

[Gideon Ackon]

from you, i know how to make any scientific project

[13blue]

Adafruit has a Lithium Ion Polymer Battery - 1200mAh, its a little cheaper and would save a shipping charge. Would it be ok to use rather than the 2000mAh?

[Honus]

Sure. It just won't have as large a capacity so it might not fully charge your device. I just built a charger using a 1100mAh cell and it works just fine. The benefit of a smaller battery is that you can make the charger a bit smaller.

[mdelzo]

Hello, Say that I charge my cellphone with four AA batteries which gives an output of 4.8V and the input of my cellphone is 3.7 V with 950mAh. will this fry my cellphone?? thank you

[Honus]

Does you cell phone charge over USB?

[mdelzo]

well i have a USB connector for the computer which i can also use to charge it (thru my computer)

[Honus]

USB is 5V so if you're trying to use 4.8V then it won't fry it. Much of it depends on how you're trying to charge it (is the voltage stable), how much current the phone will pull during charging (batteries can only provide so much current), etc. Many devices that are charged over USB require some interaction over the USB data lines so it isn't always as simple as connecting some batteries to your phone through the USB port.

[JustModIt]

where would you get the 3.7v 2000mAh lipoly battery?

[Honus]

Sparkfun- there's a link on the Tools and Materials page.

[JustModIt]

oh, thanks

[mdelzo]

Honus, What do u think of this solar charger http://www.wonderhowto.com/how-to-make-portable-solar-powered-usb-charger-with-altoids-191898/ is not as sophisticated as urs. It doesnt have a diode and the solar panel is only 4V i believe. is that going to cause a problem? thank you :)

[Honus]

Until I saw some actual numbers on how it performs or a schematic it's hard to say. I have no idea what the current output is so ther's no way to know how long it would take for it to charge something.

[antmanadam]

Could you make one without the battrie and make so it is just solar.

[dorkiedoode]

 also want to know this as well

[airsofter1]

You could, but why would you want to? It would require different wiring and you would not need the charge controller or the mintyboost. This would be cheaper but you may need a different type of charge controller. In other words this only works when it is in the sun. With the battery you could charge wihout being in the sun.

[maybe_i_dont_care]

But it's supposed to be solar powered. It says so in the introduction.

[Honus]

It is solar powered- you're using the solar cell to charge a LiPo battery that in turn provides the necessary power to charge USB devices. If you tried using a small solar cell to power a USB device while you were using the device during the day it wouldn't work to well.

[epiphone3711]

i like this circuit

[epiphone3711]

i  live in thailand 

udon thani  city

i want to circuit  sola cell charger  mobile  and any battery

[epiphone3711]

my name is amorn 

very good 

[jackelite]

 i got all of the other things needed but the jst connecter/wire was out of stock so i bought some jumper cable and a jst vertical connecter from sparkfun. will this work?

[Honus]

It should work just fine.

[iceboi714]

anyone try this on a 3GS yet?

[Honus]

A few people on the Adafruit board have tried the MIntyBoost with a 3GS and so far it's been mixed reviews- some say it works and others get an error message saying it doesn't.

[iceboi714]

Well it seems like a fun project to do. So I'll give it a go and mess around with it. Thanks

[iceboi714]

Some info on the 3G and possibly the 3GS charging...i will probably try this.
http://www.tzywen.com/modules.php?name=News&file=article&sid=683

[Honus]

That's pretty neat- they don't say if it works with a 3GS though (unless I missed that.)

Generally speaking, as long as you can provide enough current (around 500mA) and you have a reference voltage on the data pins you're good to go. A 7805 voltage regulator is pretty poor in terms of efficiency though- it's fine for a car charger but I wouldn't use it for solar power.

So far from what I've read the MIntyBoost v2.0 kit seems to work just fine with a 3GS iPhone as long as you are using a LiPo battery to charge it and you have the 100K resistors soldered in. Two AA batteries just aren't going to cut it.
There's more info here: http://forums.ladyada.net/viewtopic.php?f=15&t=11661

[iceboi714]

Thanks for the info. If im am reading correctly, I would be using 100K R on the D+ and D- to ground?

[Honus]

The MintyBoost schematic shows them being tied to the battery positive side-
http://www.ladyada.net/images/mintyboost/mintyboostv2sch.png

[iceboi714]

Just got my parts in today. WHOOHOO!!! Only 2 things I am curious about. 1. I have an empty part on the circuit board on the left hand side "PD" 2. My MintyBoost Kit 2.0 also came with a pair of 15K resistors. I don't see them anywhere on teh schematic. What are they used for?

[iceboi714]

Never mine....did some more research...got the info I needed...NOOB!!!...guess i am just a little too anxious...lol

[iceboi714]

Its complete. Everything works fine with my 3GS. I just need an enclosure for it. Thanks again for this write up.

[dmhjah]

Hi Honus, I read the FAQ question and decided to get the 6v 250mA solar cell you mention. I haven't had any luck finding a place to purchase it. do you have any suggestions? Thanks David

[Honus]

Hmmm... the place I listed was out of stock? I guess you'll just have to look around on the web.

[Sagz]

Great project! I was wondering if there was a way to use NiMH's instead of LiPo?

[Honus]

Sure- you would have to use a different charging circuit that is specifically designed for NiMH batteries.

[billd6]

So what is the total cost to build this project? Is it really cost effective

[Honus]

If you buy everything as listed it would cost $70.75 (not including the Altoids tin or shipping.) If you wanted to scratchbuild it using the MintyBoost PCB from Adafruit, building your own charging circuit and supplying your own parts from various sources you can save quite a bit. Both the charging circuit and the MintyBoost circuit are available online- just go to the web pages listed in the tools and materials section.

Both Maxim and Linear Technology supply free samples (according to their websites) of their ICs so you just need to provide all the other bits (available from places like Mouser and Digikey.) Using a slightly smaller solar cell and a 2200mAh battery it is possible to build it for a lot less:

220mAh battery
solar cell
MintyBoost PCB

After adding up the small parts for the MintyBoost circuit, a small blank PCB for the charging circuit (you would have to etch the board yourself) and a mini USB connector, you could conceivably build this for around $21.00 (not including shipping or an Altoids tin.) It wouldn't be exactly the same of course, but it would be functionally the same. I don't know if the 2200mAh battery would fit into an Altoids tin either. It would be a LOT more work of course, and there could be a fair bit of troubleshooting if you're not experienced in building these types of circuits or soldering surface mount components.

So is it cost effective? Absolutely- it just depends on the amount of work you want to do. Either way, you get a very useful and versatile solar powered charger.