Instructables

Easy solar charger and PSU [UPDATED]

Featured
Picture of easy solar charger and PSU [UPDATED]
_MG_0270.jpg
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!
 
Remove these adsRemove these ads by Signing Up

Step 1: Solar cells

Picture of solar cells
solarusb03b.jpg
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]

Step 2: Charger modules

Picture of charger modules
_MG_9657.jpg
As charger circuit you also have multiple choices. You can find circuits to charge one or more cells, with or without charge indicators (leds), and with many shapes and dimensions. Some modules only charge the battery, but others also provide +5V output voltage from the battery (usually 3.7V), pay attention to buy one this last type.
In this instructable you see two similar PCB, one has two leds to show charging process (red led) and full charge (green led), other one has no leds and is a bit cheaper. Both are meant to charge a single cell, although you can in theory connect two cells in parallel, but I don't suggest it because that will reduce their life. They also both provide +5V output.

These battery charger modules usually have three pairs of pads for connections, for all three couples of wires beware to respect the polarity (don't follow my example, try to use black and red wires):
  • DC input (also marked as "charge", "charging port", "P+ and P-", "3.7V+ and 3.7V-") where you have to connect your solar cell(s), this usually accepts from 3.7 to 6V or more.
  • 5V DC output (also marked as "increasing output" or "V+ and V-") where you will connect your device, through an USB or another power female plug, as you see in picture this voltage is very precise.
  • Battery connections (usually marked as "B+ and B-"), here connect your battery (or better your battery holder), you can also try to connect two or more batteries in parallel, but I don't suggest it.

Step 3: Batteries

Picture of batteries
solarusb06c.jpg
As battery I suggest an 18650 Li-ion cell. These are very handy, powerful, cheap and common. Also buy a clip holder. Anyway you can chose to buy a flat Li-ion 3.7V battery for cellphones, although those are not powerful as 18650 cells.

Step 4: Soft-power

Picture of soft-power
To start the circuit you have to soft-power it. That means to provide +5V to DC input with battery connected. Then you can disconnect +5V and check that the output provides +5V. To soft-power the device the solar cell can be already connected or not (to the same DC input pads), it doesn't matter.

Step 5: Prototypes

Picture of prototypes
solarusb09d.jpg
Here I tested my two prototypes. The bigger solar cell is able to charge the battery with no direct sun light, day light is enough, even in a cloudy day. With little cells you need exposing them directly at the sun. My GPS is here connected to the solar PSU and it has no internal batteries, this is pretty useful when you otherwise have buy expensive specific Li-ion cells for a device equipped with USB plug (as a modern phone or a digital camera).

Step 6: The hub

Picture of the hub
solarusb11e.jpg
Now let’s find a proper, easy, and cheap of course, way to connect devices to the charger. As you already saw I used an USB female socket to connect an USB cable to the bigger solar cell, but that was a prototype, now I want something more elegant and maybe with more than a single connection.
This is an USB hub with four USB 2.0 (you don't need 3.0 for this project, actually 1.0 is good enough) ports, each one with switch and blue led, all this for only 4$. That’s perfect! I see that there is also a +5V DC-IN socket to receive an external power source. That would be fantastic, we neither need to open it! But I want to put my tiny pcb inside it, so let’s open it to see if there is enough space.

Step 7: Some desoldering and salvage

It probably will fit, so we can begin adapting our bus. Let’s cut out the USB cable and unsolder the DC-IN socket and the power blue led, which otherwise would slowly discharge our battery. We now also have obtained a few free useful components ;-)
Before cutting the cable look where the black wire is soldered, that is the ground (-), and it’s connected with the ground pin of the DC-IN socket, we need to know where to solder the wires from the charger.

Step 8: Avoiding power dissipation

Picture of avoiding power dissipation
Then cut the trace which bring electricity to the hub's IC, since it consumes power and we don't want that. As you see in the picture, the big trace I cut is the only positive power supply to the black plastic drop which contains the hub's brain, interrupting it you'll avoid any power waste.
Beside I've discovered it's better interrupting the signal traces that come out from the black IC (the plastic drop) and arrive at second and third USB pins. I had some difficulty to power some device before doing that.
You can also decide to replace blue leds with similar red ones (which use less current) or to remove them completely to save energy from the battery, after all this solar psu has to be as much efficient as possible.

Step 9: Wire them all

I then made two couples of holes in the plastic container to let wires passing through. Use soft narrow short wires, because they have to stay inside with everything else, mine are a bit too long. After inserting wires in the holes solder  each wire’s end to the right pad.

Step 10: Attach solar panels

Picture of attach solar panels
Using double side tape, attach the pair of solar cells to the plastic surface on the side of the USB bus.

Step 11: Accommodate the pcb

Picture of accommodate the pcb
solarusb17i.jpg
solarusb18i.jpg
solarusb19i.jpg
Now search a place where to put the pcb… I thought it was simpler, I had to change three different positions. Closing the cover the pcb pushed against the components. Finally I found the best position, between switches and USB sockets. A double face tape avoid the pcb touches the metal of the sockets. Before closing remember to soft-power the device as I explained before.

Step 12: Complete with battery (holder)

Picture of complete with battery (holder)
solarusb22l.jpg
Closing the cover we keep the battery wires out. Now a 18650 clip holder is needed… mine is travelling from China to Italy together with his nine mates. So you will find here an update in a month or a bit more. For now let’s use a rubber band (from a bicycle tire) to keep wires connected and let’s attach battery with a piece of double face tape.
Maybe that pcb will reset when you take off or disconnect the battery. In that case you have to soft-power it again, notice that DC input wires are accessible from the narrow slot between solar cells and container, try to keep an easy accessibility to them, otherwise you have to open the case. Also remember to mark the wires so to know which one is positive and which is negative. Yes I know, much better to use red and black wires... :-P

Step 13: Enjoy the sun

Blue LEDs appear violet… maybe I’m color-blind and my camera has the right sense… anyway, to see if the solar charger works, measure the voltage of the battery with your multimeter, expose the solar cells to the sun light, wait a few hours, then check the voltage again, it should reach about 4.1V to be full charged. For more skeptical persons I added an image showing the GPS powered and three more devices being charged (two databanks and a GPS tracker).
Now enjoy and be sure to not enter a too dark wood ;-)

Step 14: [UPDATE]

After the right concern of many readers about the very low power (about 150 mA if I'm not wrong) of these tiny solar panels, I decided to improve my solar psu doubling the solar cells. Indeed now two more cells are connected in parallel with the first two. Output is still 4-5V but currend is double than before, so charging time (referring to the Li-ion battery under the solar cells) is half than before.
I also glued pivots between panels and case, so that the solar charger is foldable.
I've still to add the battery socket, but unfortunately shipping time is very long.
1-40 of 68Next »
maxhuey5 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... :-)

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...

USB.jpgSolar.jpg
andrea biffi (author)  maxhuey4 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)  maxhuey5 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)  maxhuey5 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)  maxhuey5 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!

chuang71 month 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)  chuang71 month 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.

thamizhmca273 months ago

I will try to this in my own.

andrea biffi (author)  thamizhmca272 months ago

great, let us know!

ajensen272 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)  ajensen272 months ago

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

manuka5 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 manuka4 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: http://www.instructables.com/id/DIY-Solarpad-Kit-...

andrea biffi (author)  manuka5 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 =>http://www.instructables.com/id/Single-AA-LiFePo4-cell-powered-project-in-a-parti/   When compared with Li-ions these LiFePO4 cells are near bullet proof ! Stan.
AbhishekGupta4 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.

mnørgaard5 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)  mnørgaard5 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)  mnørgaard5 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...

MOHD775 months ago
Good ??
Hallofo5 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)  Hallofo5 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).

BurgersBytes5 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)  BurgersBytes5 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 tank10005 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.

graghavendra5 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)  graghavendra5 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.

Hi

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

Solar panel.is 10$ for 5v 1A
Connect all.to gather enjoy

I m.importer
And retailer.
I sell.all above things at India.
Uniqueitems.in
Squidyman5 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!

You can find them in solar lawn lights. People often throw them out not realizing or caring that there are good components in them. Those lights are often made really cheap, when the plastic breaks people get rid of them. You could ask around if anyone is replacing theirs. It's amazing the stuff people throw out sometimes.

Cool! thanks, I do see those lights oftentimes broken on sidewalk paths. Ill look around for them.
Phoghat5 months ago

I've made one, but not as elegant as yours. Will now make yours ! LOL

1-40 of 68Next »