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

I wanted a charger for my iPodTouch and the MintyBoost was definitely my first choice. I wanted to take it a bit further and make it not only rechargeable but also solar powered. The other issue is that the iPhone and iPodTouch have large batteries in them and will deplete the two AA batteries in the MintyBoost rather quickly so I wanted to increase the battery power as well. What I really wanted was a MightyMintyBoost!

Apple has sold over 30 million iPodTouch/iPhone units- imagine charging all of them via solar power.... If every iPhone/iPodTouch sold was fully charged every day (averaging the battery capacity) via solar power instead of fossil fuel power we would save approximately 50.644gWh of energy, roughly equivalent to 75,965,625 lbs. of CO2 in the atmosphere per year. Granted that's a best case scenario (assuming you can get enough sunlight per day and approximately 1.5 lbs. CO2 produced per kWh used.) Of course, that doesn't even figure in all the other iPods, cell phones, PDAs, microcontrollers (I use it to power my Arduino projects) and other USB devices that can be powered by this charger- one little solar cell charger may not seem like it can make a difference but add all those millions of devices together and that's a lot of energy!

There are some really nice features about this charger:

It's solar powered!
It's small.
Large battery capacity- 3.7v @2000mAh
On board charger charges via solar, USB or wall wart. Accepts input power from 3.7v to 7v.
Remove the solar cell after charging and you have a nice compact USB power supply.
Unplug the solar cell and use the Velcro to secure the MightyMintyBoost inside a backpack or messenger bag- now plug in a larger solar cell attached to your bag for even faster charging. Using a slightly larger solar cell (6v/250mAh) you can generate enough power to fully charge an iPhone in about 5.5 hours and an iPod Touch in 4 hours.

Building this is really easy and straightforward- it only took me around an hour so follow along and build one for yourself!

Safety note and general disclaimer: Be careful cutting the Altoids tin as it can have some really sharp edges- file them smooth if necessary. Assemble this at your own risk- while it is really easy to build, if you mess something up there is the potential to damage the electronic device you are trying to charge. Be careful in your assembly and soldering work and follow good safety practices. Only use a type of battery charger specifically designed for the type of battery you are using. Please read through the entire Instructable before asking questions- if there are are any questions just ask and I'll help out as best as I can!

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)
For better performance use the Adafruit Solar Lithium charger (connections are similar but it's slightly larger- see update below)
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 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

[Landcruiser87]

Love this setup,

I plan on building a 12V system for other power hungry applications, but instead of a flimsy altoids can, i decided to beef it up a bit with a pelican project box. If anyone has any suggestions about how to cover ports a little better, that would be great.

Check it out!

Love the instructable! Great work.

[Honus]

Looks awesome. Pelican cases are great- I have a large one that's over 15yrs old and it's still going strong. Maybe for port covers you could mold some silicone plugs. Try Sugru!

[Landcruiser87]

Thanks! They're possibly one of the best made containers of any sort. I've been using them for various things here and there over the past 7 or 8 years. I like the idea of using Sugru for port covers! I was having all sorts of failed trials with grommets, silicon and other failed devices, but sugru might just be the ticket. Thanks Honus!

[Honus]

No problem- let me know how it works out!

[CODawesome]

THIS. IS ABSOLUTLY. RIDICULOUSLY. BEAST!!!!!!!!

[äbädrän]

can this solar charge charge my samsung s3???
please reply to me
my s3 battery is 3.8v 2100 mAh

[äbädrän]

if i buy a 4v and 2100 mAh battery would the phone charge?
can this solar charger charge nokia phones

[Honus]

Have a look at the FAQ page- you'll find a link to a compatibility page.

[techmajesty]

very nicely explained i will try it out i found this site after starting to build this DIY version.




Regards,
Unlock Blackberry Bold 9700

[techmajesty]

very nicely explained i will try it out i found this site after starting to build this DIY version.




Regards,
Unlock Blackberry Bold 9700

[jonsleepy]

Awesome idea! And I noticed Adafruit's new optimized solar charger, too! However, I still feel attached to AA batteries - I have several devices that use them. I would rather avoid using the lithium polymer battery packs - to me, they feel like added weight and a "middleman", even though I realize they can store more charge per gram of weight. Is there a way to get power from the panel into a circuit and into the AA batteries in the original Mintyboost? Therefore I could swap AA batteries into and out of the Mintyboost, and recharge as needed, without the use of the Lithium battery?

[Honus]

Yep, you could do that. Basically you would just substitute the LiPo cell and charging circuit. Just use two AA rechargeable batteries with a compatible charging circuit instead- you need to make sure you get the right type of charging circuit for whatever battery chemistry you AA batteries are.

[jonsleepy]

Thanks for the reply! So then there's 2 circuits.. one to convert the 1.2 (or 1.5) volts x 2 AA batteries into 5V for USB out.. and the second to convert whatever the solar panel can put out into whatever the batteries need to charge. Is that it? Say I want to charge 2-4 AA NiMH batteries. I'm not sure I know how to determine what I'd need, but I'll look around.

Actually, I found this:
http://www.instructables.com/id/Heavy-Duty-Solar-USB-Charger-In-a-tin/

but I'd want to have the option of using whatever solar panel I want, and adding more batteries. Just not quite sure how to make that modification or if this is the best way to go. Aah well, I'll get there!

Thanks.

[Honus]

That's it- the MintyBoost circuit takes your battery voltage and converts it to a stable 5V output. The charging circuit takes the output from the solar panel and uses that to charge your battery that powers the MintyBoost.

[lawidhalm]

I love this project, and thought I'm years late I had a few questions. You say it can take 3-7 volts input...what about current requirements? I ask because I'm using those garden solar cells about 4 volts each, but have a rather low current output. Does this just mean it will trickle charge all day?

Second, does this work on iphone 4s? I don't see why it wouldn't but definitely worth asking

Third, do you happen to know of a way (or an entirely different project) to modify a wall charger to then be solar powered? I feel like there should be a way to gut the ones you get at the store that plug in, use everything after they convert it from AC to DC because its designed explicitly for charging. Then all you'd have to do is connect your battery from that point on and it should work right? Just thought I'd ask - thanks!

[Honus]

The charging circuit can only pull so much current- it will max out a 500mA. The less current your solar cells provide the longer it will take to charge.

The current MintyBoost circuit will work with an iPhone 4s.

I don't know anything about modifying a AC charger to solar power. It's probably much more trouble than it's worth. To see an IPhone wall charger teardown have a look here- http://www.arcfn.com/2012/05/apple-iphone-charger-teardown-quality.html

[lluvaitech]

if i want to make this experiment, i think i should buy another batery.

[markee2]

Am building one but got some charging problem with iPhone.

Adding the circuit below can solve the problem.. maybe, anyone got some idea?  circuit copied from:
http://www.simple-electronics.com/2011/09/iphone-charger-circuit.html

[kentsfield]

Can I still charge other smartphones, like my android device (Which just uses 5V and GND)? I don't want to fry my phone because I put resistors to the data lines...

[Honus]

The version 3.0 Mintyboost works with most all Apple products (except iPad) and works with several Android phones. There is a compatibility list here-
http://www.ladyada.net/make/mintyboost/compat3.html

[kentsfield]

Thanks Honus, but I don't use the Minty Boost. I made my own little charging circuit using a 9V battery and a 7805 linear voltage regulator. I have an iPod Touch and a Android smartphone and want to charge both of them, but as I said, I am unsure if I can still charge "normal" phones with the "iMode".

[Honus]

It doesn't matter- the output is the same after the regulator. All that matters is the interaction on the USB data lines so if it is listed on the compatibility page then it should probably work- just use the same resistor values as the v3 Mintyboost.

[waterlubber]

I think you get that when the input power is too low...I've got that on a car charger.

[Honus]

Which version iPhone do you have? Which version MintyBoost circuit are you using?

[Schmidty16]

Looks good i have 1 suggestion u could put pexi glass aroud it

[dhabib03]

thanks man! but those of you using the mintyboost 3.0 kit just no need for other parts you just need a 6 watt solar panel and the minty boost 3.0 kit just assemble the kit and instead of putting the battery holder put the solar panel

[Jmorgan77]

I know that a usb is supposed to accept just 5v.Does anyone know if a 5.5v solar panel would be too high of an output for the new sparkfun charger with just the mini USB?

[Jmorgan77]

Nevermind, the data sheet says 3.75-6v input.

[Honus]

It'll work just fine.

[MyTopFan]

In the new sparkfun charger, there is a selectable 100 or 500 mah charging current. I am using a 5.5v 250mah solar panel, do for best results which should I have it set at?

[Honus]

Set it to 500mAh as that will give you the best charge rate.

[MyTopFan]

Im new to this so correct me If I'm wrong.
Could I just leave out the middle man and solder th solar panel wires straight to the lipo battery to charge it?

[Honus]

Nope- you can't do that as LiPo cells are very particular about charge rates. Connecting any power source directly to LiPo cell without a proper charging circuit would destroy the LiPo cell.

[MyTopFan]

Thanks.
one more thing, you said that the charging circuit used doesn't require a blocking diode. Since that model was discontinued, does the other one listed require a diode? ( http://www.sparkfun.com/products/10161 )
Thanks in advance.

[Honus]

You should not need a blocking diode.

[dvgs]

sweet - Thanks for the help!

[dvgs]

would a mini usb that comes on the cell phone chargers work?

[Honus]

Yep- that will work fine. I find chargers like that all the time in the trash and save them as they come in handy.

[dvgs]

In the picture your using the old lipoly charger but i have the new one that dosent come with the barral jack and the new lipoly charger looks compleatly different the the old one and i cant figure out how or were i would conecct the solar panal to the lipoly charger. Can you help me figure out were to connect the solar panal on the lipoly charger?

[Honus]

Yeah it stinks that they changed it- kind of frustrating, especially when a lot of people liked the old version.

The best way to connect the solar cell would be to connect a mini USB cable to the solar cell and then plug the cable into the board. There is a guide here that shows how to splice a mini USB cable to a solar cell.

http://ladyada.net/make/solarlipo/