Picture of easy solar charger and PSU [UPDATED]
How long does your cellphone's battery keep the charge? I guess not for long time... and your GPS? Do you have a spare battery to not lose yourself in the woods? A solution is to buy a solar charger, they're cheap nowadays, but not many of them allow you to power your device during the charging process. Indeed this is an effective solution in many cases, and saves you from using a specific battery. Therefore, what are we waiting? Let's build it!
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Step 1: Solar cells

Picture of solar cells
You can buy different types of solar cells: very cheap 2V tiny or huge and more expensive 5V 700 mAh panels. Also halfway choices are good. You need to obtain about 4-5V output voltage from them (a voltage up to 6V doesn't hurt), so if you choose the tiny cells you can connect two of them in series, with sun light they will provide 5V, although the amperage will remain very low. Scissors are there only as size comparison, don't cut the bigger solar cell to obtain many little ones!!

[UPDATE NOTE: as I said you can choose between different sizes and prices of solar panels, and if you want a charger which charges the battery in few hours in direct sunlight, or that charges in shadow too even though slower, you have to spend more and having a bigger surface and weight]
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bditewig made it!21 days ago

Thanks for the cool idea and instructions! I made one myself, and it works realy great!

hirogarden2 months ago

Trying to figure out how to build this with what I have I didn't want to hunt down the special batteries but looks like might be a good idea. I have usb base (trying to decide if I want to use a 7 plug one instead.) and got some tools but trying to figure out if the charger circuit would work as a current regulator even if I had say 4 of those batteries hooked up to it. Don't really want to blow up any of my gadgets even though I want to keep them charged while out and about.

Mr_Rep2 months ago
WHERE DO I FIND THOSE LITTLE TINY HINGES?!?!? I could seriously use those little things
maxhuey9 months ago

I got a bunch of free solar panel from a VW car dealer, they are used in new cars to keep the battery charge during transport from factory to dealer, output of each panel is about 1000 ma. at 12 volts. I bought USB cigarette lighter adapter from dollar store for $1 and connect the two together.

Now I have a 5 volt 1 amp USB charger for $1 + my labor... :-)

davidsona maxhuey3 months ago

Oh, that sounds like something I might want to try and get. What should I ask for when I go to a dealership?

Why don't you do an instructable on this?

It should be pretty straight forward if you have gotten these 12 volt solar panels and the 12 volt cigarette lighter USB adapter. Connect one to the other. I doubt if Instructable would help... :-)

and... by the way, this site used to be gadgets and stuffs, when did it turned into food channels? LOL... sorry got nothing against eating, just could not help it...LOL again falling off my chair this time...

andrea biffi (author)  maxhuey8 months ago

Yup, I need to learn to cook if I wish to post an instructable in each category

;-) That panel seems great!! I wonder where nearest VW car dealer is... a search is mandatory now!

They were originally OBDII connectors so I changed them to standard barrel plugs, much easier for isolation or diagnostic.

Go to a dealer that sells import models, locally assembled VW may not have these panels.

more solar.jpg
andrea biffi (author)  maxhuey9 months ago

cool! if you want to get rid of some of those awesome panels I'm here! ;-) actually I'm sure all Instructables community is available!

Lol... most imports dealers have these panels. You just need a good friend there. Sometimes you can find them in their garbage bin. Those are the non working panels because the wire had lost contact with the back of the solar panel. They can not be soldered, but need to glue back. I don't know what kind of glue needed though so I just insert foam pieces to keep the pressure on
andrea biffi (author)  maxhuey8 months ago

that's interesting! I should follow some of those guys home ;-)

No, I don't meant their home garbage, you might look suspicious there. Its those big metal garbage bin behind the car dealers. You'll be surprised what else they throw away. One time I found a part (US$439 door control) for my neighbor's VW - thrown away because one missing mounting bracket that can easily make with a small piece of Aluminum. Them dealers do not repair, they just replace in order to sell parts - bigger profits paid by customers...

andrea biffi (author)  maxhuey8 months ago

LOL! Ok, but I'll look suspicious behind the car dealer too!

Anyway you are right, they throw away very expensive and almost new stuff!

chuang75 months ago

Hello, I'm just wondering what type of wire I should use? I'm looking at 26~28 gauge. Is this too thin or too thick? Thank you!

andrea biffi (author)  chuang75 months ago

Don't worry too much about that, any thin wire is good, thinner is easier to use. 28 gauge holds more current than needed.

thamizhmca277 months ago

I will try to this in my own.

andrea biffi (author)  thamizhmca276 months ago

great, let us know!

ajensen276 months ago

ok i like what you did but i want ask you a question. i have a usb hub and a USB cable and several solar lights like four and I think they put out around five or six volts. how do I check the amperage and could I use the USB car charger that I plug into cigarette port. I can solder and wire things but don't know how they will interact and if they will get the job done. all I want is a solar charger for my cell phone bc I work all day in middle of a construction site. it won't be used for much else. can you help with advice on what all I need.

andrea biffi (author)  ajensen276 months ago

What are the dimensions of the panels? if they are tiny they probably are not powerful enough...

manuka9 months ago

Well shown, but I'm wary on several fronts-

* With PVs attached like this naturally the whole setup needs to be placed out in the sun! The internal electronics may hence become cooked & the Li-ion cell overheat! (It happens - I've had such setups destroyed here in "down under" NZ due to excessive solar heating). Best use flying leads so the PV can be put in the sun while the energy store stays in the shade (or shelter).

* LiFePO4 cells (3.2V) are much more rugged & tolerant. Li-ions can be VERY dangerous if charged/discharged out of spec.!

* Chargers like this left outdoors may be stolen,animal (dogs!) or rain damaged.

* Such small PVs have a really pathetic output - best go for something MUCH larger. (Even with 4 hours of bright sun a setup like yours would take DAYS to recharge!) Since you may need to charge the phone on a less sunny day I'd say something in the 2-5 Watts range may be needed. A 12V PV automotive trickle charger (~$US10) may tempt, but these are usually quite bulky.

Solarcycle manuka8 months ago

Yes, you want to keep the battery away from the sun. Not only can it decrease the battery life, but the charge circuit can overheat and shut off. Also, you're essentially charging two devices, the external backup battery and your phone, at the same time. This instructable explains what kind of charge controller and power is required to perform this task and give constant phone charge even under non-ideal conditions:

andrea biffi (author)  manuka9 months ago

Hi thanks for suggestion! Yes, it's better not to overheat Li-ion cells, the soalr panel should protect it, but maybe it's not enough.

Some of these Li-ion cells have a protection circuit, as mine, I will add a note to pay attention to that. They are a bit more expensive but they work better, they last longer and they are safer. I didn't know about LiFePO4...

Yes these solar panels are tiny and with a pathetic output, I will soon add an USB hub to the bigger panel you saw on the other prototype, it has 3.5W power. Anyway, principle is the same, and the more you spend the more efficient the charger will be, weight included ;-)

Great - you may care to check my LiFePO4 based Instructable =>   When compared with Li-ions these LiFePO4 cells are near bullet proof ! Stan.
AbhishekGupta8 months ago

We are living in interesting times. As our need for information and connectivity grows it is key to remain "powered up" at all times. Things like this Easy solar charger and PSU brew independence fostering mobility while charged. This may look like a small thing but if you look at it from a perspective of sign of times then its just awesome! The price of these things is also becoming more and more affordable going the cellphone way.

mnørgaard9 months ago

Awesome - Love it! I know next to nothing about electronics but want to get started and this looks like a cool project. I've heard a lot of good things about super-capacitors - what are your thoughts about using these to store the power? They seem a lot cheaper than batteries.

andrea biffi (author)  mnørgaard8 months ago

I'm not sure they are so cheap, but I'm not very skilled in that topic... maybe they are safer than Li-ion cells.

andrea biffi (author)  mnørgaard9 months ago

If I'm not wrong super-capacitor and this type of batteries have pretty much the same price, but as user "manuka" noticed maybe Li-ion are dangerous being left on sun, maybe super-capacitors are safer...

MOHD779 months ago
Good ??
Hallofo9 months ago

Good looking build! Your directions are clear and pictures helpful. The only thing I would add is a schematic to show the wire routing/etc.

For this project I doubt you would save that much money, but you get the satisfaction of "doing it yourself" and learning (or practicing) basic electronics skills.

andrea biffi (author)  Hallofo9 months ago

Hi Hallofo, you can see the entire wired circuit in 2nd photo of Step9, but since different models of pcb have different pads' positions and labels, I suggest you to refer to the generic list in Step2, just pay attention to right polarity (not a big mess, since they are just three couples of wires).

BurgersBytes9 months ago

Ditch the yellow wires and give people a schematic for goodness sake!

I'm confused. A 3.7 volt battery cannot run 4 USB ports or charge 4 phones. The charger may output 5 volts to the USB, but not to 4 devices. Which is more important? Charging the battery or charging the phone?

Wouldn't you need one charger for the phone port and one for the battery? Since you have the charged battery couldn't it be used to charge the phone. Nice pictures of spaghetti colored wires.

"A 3.7 volt battery cannot run 4 USB ports or charge 4 phones"

The circuit that the battery and solar panel are connected to steps the power up to 5v so it does not matter that the battery has a lower voltage.

"The charger may output 5 volts to the USB, but not to 4 devices."

It will the amps will just be divided by 4, so the devices will charge slower and the battery will run out faster BUT it will put out 5v until it has no more power

"Wouldn't you need one charger for the phone port and one for the battery?"

The phone is charged over usb and has its charging circuit integrated inside the phone and the charger for the battery is what the blue PCB does.

"Since you have the charged battery couldn't it be used to charge the phone."

That is what the circuit (blue PCB) does, the battery is more or less a buffer.

"Ditch the yellow wires and give people a schematic for goodness sake!"

Judging from the questions you asked and the contradicting statements after, you clearly have no idea how the circuit works and a schematic would probably be getting a bit over your head. Before complaining about schematics you should probably learn basic wiring or even reading lables. :)

Your last picture of the battery says it all. Even you had to mark it red to tell yourself the polarity. Color coded wires or a schematic of board connections should have been a no brainer in any electrical Instructable..

andrea biffi (author)  BurgersBytes9 months ago

I quote from Step12: "Also remember to mark the wires so to know which one is positive and which is negative". No need to justify my choices, but just to satisfy your curiosity I'm using a bunch of spaghetti colored wires which exceeded from another project.

sb4 tank10009 months ago

I don't think that statement is correct "amps will just be divided by 4". If you charge 4 phones, the load resistance is effectively divided by 4 -- the voltage will dip unless you supply 4 times the current. If the regulator can do that, fine, I agree with second half of statement that battery will run out faster and still supply 5V.

graghavendra9 months ago

honestly, when its consider as DIY project. i can say its OK OK

as its not new at all, no savings in it. nothing to learn in it except connection

but i appriciate using HUB.

better doing this by paying huge. buying a solar power bank is sujjested.

if not, buy a power bank from china at 5$ break that info pieces to get circuit battery everything at best price.

again, i suggest every one to use solar panel 5v 1000ma

because we always wont obtain max power.if u really want to use this in real life everyday, then must use big solar panel

final cost of this product to be finished at 10$ to make it cost effective.

andrea biffi (author)  graghavendra9 months ago

Bbut notice that in 5$ cheap solar banks you usually have to manually switch between charging and supplying energy, I already have a pair of them. Besides I like to Make it and share it, and since it's so simple it means many people can build it and enjoy.


Power bank pcba is 0.5$. Case 0.5$ battery 2$
All to gather max 5$. Quality battery mean 10$ max in.retailer

Solar 10$ for 5v 1A
Connect gather enjoy

I m.importer
And retailer.
I sell.all above things at India.
Squidyman9 months ago

Hi, that was a very useful and potentially life saving instructable for all the Boy Scouts in the world (like me)! From my experience, solar cells are expensive to buy in the epoxied version and are cheap but break easy with non coated ones. Where do you buy them for the best price? Thanks!

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