Step 1: Tools and materials

Picture of Tools and materials
Here's what you'll need to build your own MightyMintyBoost:

Soldering iron
Wire cutters
Pliers (or muiltitool)
Metal shears
Clear packing tape

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!

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-

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.
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GabrielB72 months ago

Should the battery be the polymer version, or can it be a regular lithium-ion battery? I'm noticing a rather substantial price difference between the two.

Honus (author)  GabrielB72 months ago
The charging circuit is suitable for either Lithium Polymer or Lithium Ion.
GabrielB7 Honus2 months ago
stukz5 years ago
what is the total coast of all the parts?
Honus (author)  stukz5 years ago
Look in the FAQ section- it's all there.
from you, i know how to make any scientific project
13blue5 years ago
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 (author)  13blue5 years ago
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.
mdelzo5 years ago
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 (author)  mdelzo5 years ago
Does you cell phone charge over USB?
mdelzo Honus5 years ago
well i have a USB connector for the computer which i can also use to charge it (thru my computer)
Honus (author)  mdelzo5 years ago
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.
JustModIt5 years ago
where would you get the 3.7v 2000mAh lipoly battery?
Honus (author)  JustModIt5 years ago
Sparkfun- there's a link on the Tools and Materials page.
JustModIt Honus5 years ago
oh, thanks
mdelzo5 years ago
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 (author)  mdelzo5 years ago
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.
antmanadam5 years ago
Could you make one without the battrie and make so it is just solar.
 also want to know this as well
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.
But it's supposed to be solar powered. It says so in the introduction.
Honus (author)  maybe_i_dont_care5 years ago
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.
i like this circuit
i  live in thailand 

udon thani  city

i want to circuit  sola cell charger  mobile  and any battery
my name is amorn 

very good 
jackelite5 years ago
 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 (author)  jackelite5 years ago
It should work just fine.
iceboi7146 years ago
anyone try this on a 3GS yet?
Honus (author)  iceboi7146 years ago
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.
dmhjah6 years ago
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 (author)  dmhjah6 years ago
Hmmm... the place I listed was out of stock? I guess you'll just have to look around on the web.
Sagz6 years ago
Great project! I was wondering if there was a way to use NiMH's instead of LiPo?
Honus (author)  Sagz6 years ago
Sure- you would have to use a different charging circuit that is specifically designed for NiMH batteries.
billd66 years ago
So what is the total cost to build this project? Is it really cost effective
Honus (author)  billd66 years ago
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.

dmhjah Honus6 years ago
HI, I purchased the solar cell you have listed here and wanted to know how do you tell the positive end from the negative end. Thanks David
dmhjah dmhjah6 years ago
On the back there are some leads that are taped down -- kinda looks like tensel. Those leads can be lifted up before you reach the part that is taped. Do I need to remove the leads and tape?
Honus (author)  dmhjah6 years ago
No, you don't need to remove the leads and tape. You can solder directly to the leads.
Honus (author)  dmhjah6 years ago
The easiest way is to attach a multimeter to the leads.
Who said anything about "cost effective"? We're trying to save the planet here!
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