The "mini solar book", torch and charger

Picture of the
The "mini solar book" is another solar power supply and charger, which acts as LED light too.
Its torchlight function is very useful and effective. Indeed white LED only consumes 20 mA, so it will provide light for about 30 hours with a single charge of the battery, and with solar cells addition its life is practically endless. Of course you can also use this device to power your cellphone, your GPS logger, or any other little USB gadget (although battery has a reduced capacity due to its small size).
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Step 1: The USB hub

To provide the connection to most devices is good to use an USB female socket. You can find many of them in USB hubs. This model has four USB 2.0 ports, you don't need 3.0 for this project, and actually 1.0 is good enough. 
Cut the circuit board in two and keep the smaller part with two USB sockets.
You can save remaining ports and USB plug for next projects.

Step 2: Solar cells and battery

Picture of solar cells and battery
I used very cheap 2V tiny solar cells. We need to obtain about 4-5V output voltage so let's connect two of them in series, indeed they will provide up to 5V in direct sun light, although the amperage will remain very low.
The battery is a small flat Li-ion 3.7V battery for cellphones, these are not powerful as 18650 cells but they are very small and a great choice for a project like this.
I opened the plastic case and extracted the Li-ion cell, with its protection circuit. Keep half case as cover and safe protection.
Smatsh1 month ago


A technical question : I have a 5V solar cell but they are "only" 250mA each. Can I connect them in parallel to increase the intensity ?

Very nice Instructable, simple and effective, the best :)

andrea biffi (author)  Smatsh1 month ago
yes you can, look my other solar instructable, I connected two and two in series and the two pairs in parallel, to reach double voltage and double intensity

Exact! Thanks for the answer :)

I love the idea of the pivots btw

I'll keep you update of my projet!

adnankhans1 month ago

hello Every One Can help me for make this circut or buy from any store Please Give me Links Or Help Me Make

siamex2 months ago

good job man this thing really helping me out keep up the good work.

Jan_Henrik2 months ago

Very cool!!!

Wow! Nice work! I could see this as a useful tool in many ways. How about a solar wallet?
andrea biffi (author)  KyleTheCreator2 months ago

then you need also a transparent pocket! ;-)

Flameofglory3 months ago

Thank you for showing me how to make this. I made a larger scale version to charger my airsoft batteries while I was on the field.

Thanks :)

andrea biffi (author)  Flameofglory2 months ago

I'm glad of that!

lukester294 months ago
I like your last solar charger but I love this one! Your really should sell this stuff because people like me define tilt would
andrea biffi (author)  lukester294 months ago

thanks! do you think people would like more to buy a kit ready to build or a gadget ready to use?

you can sell both. Many people want to build there own, but hate the time and confusion of sourcing all the apropriate parts. There are also many people that just want a finished gadget.

andrea biffi (author)  thedustycelt4 months ago

you are right.. I will plan to collect some kits and assemble some devices... maybe a kickstarter could help..

very beautiful idea!! congratulations andrea

hunter9994 months ago

Wow, this is a ingenious idea! This could be so handy 'cause of its size. There are a lot of possibilities for this, awesome job! :-)

andrea biffi (author)  hunter9994 months ago

thanks my friend!

astral_mage4 months ago

try going to or 4 yr charging usb gear.