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

intro
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introHow 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!
How to make a solar iPod/iPhone charger -aka MightyMintyBoost
MMinty2.jpgMM22.JPGMMinty1.jpg
 
 

step 1Tools and materials

Here's what you'll need to build your own MightyMintyBoost:Tools:Soldering ironScissorsWire cuttersPliers (or muiltitool)MultimeterMetal shearsClear packing tapeMaterials:M…


step 2Build the Minty Boost kit

First build the MIntyBoost kit according to its instructions. It's really easy to assemble- even a complete novice can do it.Instead of connecting the battery holder in the…


step 3Add the battery and charger

Now cut a notch out of the other side of the Altoids tin to fit the charger and secure the charging circuit to the bottom of the Altoids tin with double sided adhesive. Rec…


step 4Add the solar cell

There are a couple of different ways to connect the solar cell. The first is by simply shortening the connector leads and plugging the barrel plug into the barrel jack on t…


step 5FAQ and additional info

Here's a list of frequently asked questions:Q: Is it possible to overcharge the Lithium Polymer battery?A: No- the charger will automatically switch to trickle charging and…


469 comments
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Nov 3, 2009. 9:27 PMbfulton says:
 I have built this with the exception of using the 6Ah battery instead. My problem is that after fully charging the 6Ah battery, I still only get around 2 full charges on my iphone 3g, any ideas as to why I'm not getting 5 like I expected?
Nov 3, 2009. 9:51 PMHonus (author) says:
No idea. You should really get about 4 charges on it since the Minty Boost circuit is about 82% efficient.  Are you unplugging the iPhone immediately after it's charged? If you leave it plugged in it will still draw power even if it's fully charged- it basically thinks it's plugged into a wall outlet.

Nov 3, 2009. 9:57 PMbfulton says:
 No, I have charged it overnight, so I don't unplug it till I wake up. I am recharging the pack via the wall wart again now (it should be full tomorrow at noon) then I will try charging while I'm awake so I can unplug when it's full. Thanks for the advice, I'll let you know how it turns out.
Oct 28, 2009. 11:43 AMskr5e says:
I just finished this project as my first DIY project, and everything's working perfectly, except I'm having problems securing the mintyboost board bottom of the altoids box by using double sided adhesive. The bottom surface of the board is very uneven because of the soldering and it doesn't make much contact with the adhesive. Any suggestions as to how I could stick it down?

ps someone suggested museum wax, all that did was make it gunk up with wax, didn't help sticking it down at all.

Thanks in advance for suggestions

Oct 28, 2009. 4:27 PMHonus (author) says:
You might try using a hot glue gun. Just rough up the bottom of the Altoids tin with a bit of sandpaper first to help the glue stick to it.

Oct 29, 2009. 8:20 PMskr5e says:
Thanks! hot glue worked great.

Oct 10, 2009. 4:59 PMwingrider78 says:
Honus, I just want to say that this is an awesome idea...this will be my first attempt at a project like this and I have a couple of questions...

1.  When hooking the solar cell up to the charger board, there are 3 JST plugs, one is for the mintyboost, one is for the battery, is the other one for the solar cell???  You mentioned that you used a spare two pin cable that you had and soldered it on the 5v line...I purchased a spare JST and thought it would go to the third connector...am I correct?

2.  using the 2200ma battery, when charging my blackberry extended battery, 1500ma, in theory I should be able to get 1.5 charges out of the 2200ma battery right?  Will the MMB battery continue to push out charging power until it has nothing to give, or will they reach an equilibrium somewhere in the middle???



Oct 10, 2009. 7:24 PMHonus (author) says:
1. You are correct. The third JST connector is so you can plug in a power source to the 5v input for the charger.

2. You should be able to get approximately 1.5 charges out of the 2200mA battery but it may be slightly less as the MintyBoost circuit isn't 100% efficient. Once your device is charged you should unplug it as many devices will think they are connected to a wall outlet and will continue to draw power if they are in use.

Oct 28, 2009. 10:36 AMTv1996 says:
Can you add a 4 port usb hub to the device?  I wanted to be able to use usb powered speakers and my ipod together, both powered by this.

Oct 28, 2009. 11:22 AMHonus (author) says:
I haven't tried anything like that so no idea- I say give it a go and see what happens!

Oct 11, 2009. 9:19 AMwingrider78 says:
1.  I thought so, thanks for the clarification

2.  Thanks, sounds good to me.

Oct 10, 2009. 5:03 PMwingrider78 says:
One other question...is there a possibility that the battery holder from the minty boost could also be soldered on along with the JST cable, so the power could come from either side???

That way if there wasn't enough charge from the LiPo battery, I could just pop two AAs in and put some emergency charge on my device.  Maybe just have to unplug the JST from the charge board or something.

Oct 10, 2009. 7:29 PMHonus (author) says:
Well yes and no- depending on how you do it. If you try to plug the two AA batteries into the 5v input on the charger it won't work because the charger has a minimum required input voltage that the two AA batteries can't meet.

You would essentially have to disconnect the charger and LiPo battery from the MIntyBoost circuit and connect the two AA batteries directly to the MIntyBoost. You could probably just rig up a little slide switch to tell the MIntyBoost where to get the power from.

Make sense?

Oct 11, 2009. 9:17 AMwingrider78 says:
That makes sense.  I wasn't sure if just soldering both the battery holder and the JST that connects to the charger board would cause any problems.  My process would have been to pull the minty boost JST from the plug if I were going to use the AA batts and to leave the batt holder empty if I was going to use the LiPo battery.  Would that cause any problems with them both connected without a switch??  So when looking into a selector switch I just need to find one that can handle mintyboost output power of 5v and 400ma???

Oct 11, 2009. 12:31 PMHonus (author) says:
The biggest issue is that you can't have the batteries connected to the charger while the charger is outputting current- other than that you're OK.

I would imagine almost any little selector switch could handle that much current.

Oct 14, 2009. 8:44 AMwingrider78 says:
Thank you for all your help...I have purchased an ON-OFF-ON rockerswitch that I plan to use.  Since this is my first try at makinganything like this myself, I just want to be certain of thewiring...I am assuming that I will take both black wires (one fromoutput JST from charger board and the other from the battery holder) andsolder them together on the neg side of the mintyboost board.  andthen each positive to the proper pin on the switch, then the output pinfrom switch to the positve of mintyboost...am I thinking properly???

I have the mintyboost already soldered up and it is currently chargingmy Blackberry Curve 8320 off two AA batteries...got it first try:)  Now I am just waiting for the items from Sparkfun and my switchto get here...can't wait :)

Oct 16, 2009. 10:55 PMHonus (author) says:
That sounds right to me. Make sure to post pics when you're done!

Oct 19, 2009. 11:03 AMwingrider78 says:
Here is my attempt at a Might Minty Boost, with the added functionality of a switch installed to still use the AA battery holder that comes with the mintyboost kit.  Take a look at the pictures and let me know what you think...

The case is a "reused" watch or bracelet case...I wanted the clear lid so I could still see the charging light from the top on the LiPo charger board.  Need some more practice with my "dremel" tool, but I got the job got done.  Flush mounted the solar cell as much as possible (I would have greatly preferred to have the solar cell INSIDE the lid, but didn't have a box big enough).  Needed some hot glue to secure the Minty Boost board, the included foam tape didn't really work well for it.


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Oct 27, 2009. 12:46 PMdeadpieface says:
that is very neat idea. . . looks good too.  thanks to both of you!

i got a hold of the original idea for my blackberry...this is a nice addition to it!
Oct 19, 2009. 7:48 PMHonus (author) says:
Looks great! Everything work the way you wanted?

Oct 20, 2009. 6:17 AMwingrider78 says:
Thanks!!  It works the way I wanted it to...the switch is great...not sure how much I'll actually use the AAs, but they are there if I need them...the only downfall to the whole system is the solar cell.  I have a couple other 12v solar maintainers that are amorphous cells and can still put out 16v in very very cloudy bright days...the one on this charger pretty much needs direct sunlight to give the needed 3.7v to activate the charger.  It will work, but just won't charge as long per day as I was hoping it would. 

Cosmetically, I hoped I would have done a better job getting the holes cut out...oh well, it works :)

Oct 22, 2009. 1:56 PMwingrider78 says:
What could my problem be that the charge led is not blinking for trickle charge...I haven't ever seen it blink yet.  I had been charging via usb to get the lipo up to full charge...woke up this morning and the led of off.  I measure the batt voltage and it was 4.18v.  I assumed this was fine since I remember reading that the max was around 4.2v.  I left the usb plugged in and tested it an hour later and it was 4.21...so it appears to still be charging, but the led is off.  I then unplugged the usb, and an hour later the batt tested at 4.15v...is that normal or is something going on that I need to address??  I am charging with my switch turned off, so there is definately nothing drawing power off the middle (SYS) jst connection...

Also...when using the JST conncetion with the solar panel, I understand that the panel itself is limited to 100ma...BUT what is the JST connection limited to...the usb input is limited to 100ma, the barrel plug is 280ma, what about the jst???

Oct 22, 2009. 7:14 PMHonus (author) says:
It doesn't blink very long before shutting off. I think everything is functioning normally. The JST input into the charger is tied to the same line as the barrel plug so the current is limited to 280mA.

Oct 23, 2009. 5:28 AMwingrider78 says:
I recorded the MMB charging yesterday just to find out if the led did in fact blink and it does not.  The led just goes off, it never blinked once...but if everything else is normal, I guess I just won't worry about it...

Okay, just ran some tests last night with charging my blackberry.  The battery in my blackberry is 1100ma and was at 45% when I started charging, the lipo battery was full...

Time -  lipo volts - BB% charge
5:25p - 4.21v - 45%
5:45p - 3.75v - 80%
6:00p - 3.73v - 85%
6:30p - 3.75v - 95%
6:50p - 3.74v - 100% and charge indicator on BB was off

This morning the volts on the lipo read 3.79...Just trying to find out if these are normal/good numbers to be getting

Oct 23, 2009. 6:18 AMHonus (author) says:
I don't have a Blackberry for comparison but that sounds about right to me.

Sep 25, 2009. 5:57 PMripstikfan says:
how much would all of the parts be combined?
Sep 25, 2009. 8:12 PMHonus (author) says:
Please read the FAQ section.
Sep 26, 2009. 6:25 AMripstikfan says:
oops didnt see that
Sep 24, 2009. 6:08 PMJohn H Doe says:
Would someone list the parts of the MightyMintyBoost? I have the some parts already figured out but Im not sure about the rest. I would buy it made but were's the fun in that?
Sep 24, 2009. 7:04 PMHonus (author) says:
There is a complete listing on the MintyBoost web page.
http://www.ladyada.net/make/mintyboost/parts.html

Sep 24, 2009. 8:05 PMJohn H Doe says:
Thanks so much! I was looking http://www.ladyada.net/make/mintyboost/process.html here for the parts, no wonder I couldnt find them all...

Sep 20, 2009. 4:36 AMclzfishing says:
can u cut a solar panal cuz I might just mount the solar panal to my phone or my ipod.
Sep 20, 2009. 7:08 PMHonus (author) says:
I've never tried to cut one so I don't have any idea. I would imagine they would be pretty difficult to cut and easily damaged so I'd try to find a solar cell that works within your necessary dimensions.
Sep 15, 2009. 6:31 PMmartzsam says:
I want to use this project as a power source for my lego nxt using richiehops's Instructable to power the nxt via usb on a computer. Does the charger put out power constantly? Would I be able to step up the voltage using the 5v to 9v voltage converter? Does it give the same amperage as a normal usb port?
Sep 15, 2009. 6:59 PMHonus (author) says:
The MintyBoost circuit can put out around 400mA. USB 2.0 spec is 500mA max current. There's no reason why you couldn't step up the voltage to 9v with the proper converter. I don't know about it putting out constant power.....
Sep 15, 2009. 7:20 PMmartzsam says:
I need it to put out constant power otherwise I run the risk of damaging my nxt unit, how long is the solar unit able to supply power for?
Sep 15, 2009. 7:27 PMHonus (author) says:
It all depends on the current draw of your NXT system. At 500mA draw a 2000mA LiPo will last four hours- that's before you boost the voltage as the boost converter has some energy loss.
Sep 15, 2009. 7:22 PMmartzsam says:
Also, I would have to run several in series get at least 8 total amps out of the solar cells, is there a cheaper way to do this?
Sep 15, 2009. 9:20 PMHonus (author) says:
8A current draw? Or do you mean you need 8Ah capacity?
Sep 16, 2009. 8:26 AMmartzsam says:
I mean the nxt needs at least 8 amps to fully power itself.
Sep 16, 2009. 4:13 PMHonus (author) says:
That's some juice- you're definitely going to need something a lot more substantial than a single LiPo cell and a MintyBoost.
Sep 18, 2009. 1:23 PMmartzsam says:
My original plan was to Make a solar charger for the lithium ion battery pack for the nxt but hit a road block when I found out it charges on ac power instead of dc. So I tried solar powering a dc-ac inverter but the solar rig would cost around 300 dollars and take up about 20 square feet. Do you have any suggestions?
Sep 19, 2009. 7:39 AMHonus (author) says:
What are the specs (voltage and capacity) for the lithium ion battery pack?
Sep 20, 2009. 8:19 AMmartzsam says:
8 volts but I can't find the capacity anywhere.
Sep 20, 2009. 7:06 PMHonus (author) says:
So basically what you need is a charger that accepts a DC input and can charge an 8 volt lithium ion battery. Then you just need to match your solar cell to the charger. There are a lot of chargers that run off 12v that are designed to charge lithium batteries for radio control cars and airplanes- I'd say that would be a god place to start.
Sep 21, 2009. 1:45 PMmartzsam says:
ok. Thanks for the help.
Sep 9, 2009. 1:29 PMDantex says:
i saw 6 mah battery at sparkfun
do you know would it fit inside altoids?
Sep 14, 2009. 10:50 PMsreeci says:
Thank you very much.
Kumar
Sep 9, 2009. 3:44 PMHonus (author) says:
Unfortunately it won't fit- it's too thick to fit inside the tin along with the other electronics.
Sep 14, 2009. 6:54 PMsreeci says:
For heaven's sake.. will any one please tell me the value of R4 & R5? thank you
1-50 of 469

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