Introduction: Rain or Shine Solar Charger

Picture of Rain or Shine Solar Charger

Have you ever wanted a waterproof, weatherproof, lightweight portable solar charger for small electronics? Whether you're a backpacker, a survivalist, or just trying to preserve the planet so you can enjoy it outdoors a little longer, this is the project for you.

About a month ago I was on an 8 day backpacking trip through Shenandoah National Park. I'd arranged to have a friend meet me for re-supply halfway through. Unfortunately, I'd fallen in with a fast crowd and was 27 miles past where we'd arranged to meet. Fortunately, I was carrying my cell phone, which typically has about a week of standby time. Unfortunately, away from civilization the signal is much weaker, so unbeknownst to me I only had about a day and a half of standby in this case. I found this out on day three. I began thinking about backpackable solar charging solutions. I did manage to yogi a cell phone and get ahold of her, but in a less busy park things might have gotten really out of hand.

I'd had fantastic weather until day six, when I got hit with real backpacking weather: thunderstorms and cold, driving rain. When I got home, my digi-cam had water damage. It mostly works, but sometimes won't turn on or turn off now, and the LCD has cloudy water spots, this despite being inside a ziplock bag inside my pack. I began thinking about lightweight waterproof electronics enclosures.

Then, I started thinking "Hey, I can do both at the same time!" Nine prototypes later, this is what I had, the "Rain or Shine Solar Charger." In addition to being useful for backpacking, this charger attaches with parachute buckles, so you could attach it to a messenger bag, or a bookbag, or hang it in your kitchen window. It takes about ten hours to charge a typical cell phone, but it's a storage charger, so you could leave the charger in the sun to collect energy during the day, then plug the cell hone in at night to charge from the stored energy.

This is a fairly complicated project, which will likely stretch either your sewing skills or your electronics skills, but the results are well worth it.

If you'd rather skip all that and simply purchase this one, the Etsy link is

Step 1: Software: Sewing the Waterproof Pouch

Picture of Software: Sewing the Waterproof Pouch

The sewing half of this project is making a waterproof zippered pouch, somewhat larger than the flexible solar cells that we will be using to power it. The pouch is primarily constructed from a silicone-impregnated ripstop nylon called SilNylon. This is a lightweight, totally waterproof material that is becoming ever more popular in backpacking circles. You'll need the following materials, I purchased them from

SilNylon, 6.5" x 13"
#3 waterproof continuous coil zipper, 5 3/8"
#3 zipper pull
1/2" nylon webbing, 6"
2 1/2" parachute buckles
100% rayon thread. (cotton/poly snags!)

First, cut a rectangle of SilNylon, 6.5" x 13." mark for the seams 1/2" away from the long edges, and 1/4" away from the short edges.

Next, cut a piece of continuous coil zipper to 5 3/8" long. Open it up from one end about 2" and insert the zipper pull. Slide the zipper pull to the middle of the zipper. Stitch across the ends of the zipper on both sides to prevent the zipper pull from coming out as shown in the image.

Step 2: Attach the Zipper and Form a Flap.

Picture of Attach the Zipper and Form a Flap.

Before we start sewing, here are a few quick notes on working with SilNylon: I found very small stitches, about 20 per inch, to work best. Avoid pins wherever possible, because you'll need to seal all seams and pinholes to be waterproof. One very nice thing about it is it doesn't seem to fray at all, due to the silicone impregnation guing the threads together. It feeds poorly through your machine, because its very slippery, and it snags cotton/poly thread.

Okay, we're going to be attaching the zipper and forming a flap which covers it. This is constructed much like the fly of a pair of pants. Remember that we want the shiny side of the zipper facing out when all is said and done.

First, center the zipper along one edge, shiny side down, and stitch 1/4" away fron the edge.

Next, fold the fabric back 1/4" past the zipper and run a topstitch as shown in the picture. This will form the flap covering the zipper.

Step 3: Complete the Zipper

Picture of Complete the Zipper

Next, open the topstitched flap up, and fold the fabric in half backwards, such that the opposite edge is behind the shiny side of the zipper. This will form a loop of fabric. Sew the other side of the zipper to the fabric.

Step 4: Align the Zipper and Flap

Picture of Align the Zipper and Flap

The next step is to roll/fold the fabric such that the flap is flat and covering the zipper, and the edge of the flap is aligned inside the edge of the loop of fabric. We're inside-out at this point. Use a pair of pins through the outside seam allowance, because its critical to have the alignment right here. Once everything is alogned right, use you fingers to press a crease into the top and bottom of the fabric.

Step 5: Sew Up Both Sides to Form the Pouch

Picture of Sew Up Both Sides to Form the Pouch

With everything aligned, sew up both sides of the fabric to create the pouch. Start with a plain stitch along the black layout lines we made in step one, then fold the excess fabric in half and topstitch it. This will make the seams inside 4 layers thick, which is important because these are what we'll be attaching the batteries and electronics to later. You should now have an inside-out pouch that looks like the picture.

Step 6: Invert and Check

Picture of Invert and Check

Now its time to check your work. Open the zipper up and invert the pouch through the zipper opening. You should end up with a 5.5x5.5" pouch with a hood covering the zipper. If it looks right, attach 1/2" webbing to the top two corners as shown in the picture. Sew through the now inside out seam, because that area is 6 layers thick instead of two.

Step 7: Attach Buckles and You're Done Sewing

Picture of Attach Buckles and You're Done Sewing

Now attach buckles to the webbing, and you're done sewing! Use a silicone-based seam sealer like Sil-Net to seal all the exposed seams and stitching. If you don't seal it well enough, your electronics will get wet, and that would be a Very Bad Thing (TM)

Once the seam sealer has dried, put away your sewing machine, and get out your soldering iron iron and multimeter, its time to make a solar charger!

Step 8: The Hardware: an Ultralight Solar Charge Controller

Picture of The Hardware: an Ultralight Solar Charge Controller

The solar charger has four main subsystems. I'm going to spend a few minutes going over them. Feel free to skip this page if you care more about the "hot to make this" than the "why this works," as it runs a little long.

The solar cells. The cells we are using are flexible, thin-film plastic cells. They convert sunlight into electricity. In our case, our solar array puts out 3 volts and 150 milliamps in full sun, and less than that in cloudy, hazy conditions. The voltage and current provided by the cells is variable, so we'll need a way to store the energy in a more useful form. For this, we need

The storage battery. We'd really like to just hook the solar cells to the cell phone and call it a day, but this doesn't work because much of the time they can't put out enough instantaneous power. So we'll store the solar energy in an intermediate battery which can provide high power.

The solar controller. This circuit detects when the batteries have stored up a useful amount of energy, and turns on the cell phone charging regulator. Then it monitors the amount of energy in the storage battery, and turns off when the storage batteries are depleted.

The DC-DC converter. The solar system runs at a variable voltage between 2v and 3v. To charge the battery we need a regulated 5V DC. This is accomplished by using a DC-DC converter, in this case a lightweight universal converter called an AnyVolt Micro.

When I initially envisioned the charger section, I had planned to do it the easy way: a solar panel feeding a regulator which would trickle charge the battery. Unfortunately, Motorola decided that this wouldn't be possible - my Motorola V325 phone requires at least 100 milliamps of charge current, or it will continually cycle the charging circuitry on and off. This actually depletes the battery rather quickly instead of charging it, which is the opposite of what we want. In full sun, the solar cells I'm using provide 3V and 150 milliamps when wired in parallel. This isn't enough power to sustain a 100 milliamp charge current under real-world conditions, where we have cloud cover, tree cover and time of day to contend with.

This is the exact same problem that full-scale solar power systems have to contend with: peak power demands often exceed the abilities of the solar cells. We're going to solve the problem in the same way: by using a storage battery. In this case, I've used two AAA NiMH batteries in series. These are charged at all times by the solar cells through a diode. The power output of the solar cells is moderate enough that we don't need to add any other circuitry to prevent overcharging the batteries.

However, we will need a circuit to start charging the cell phone when the storage batteries are charged, and stop charging the cell phone when the storage batteries are depleted. This will prevent the cycling problem - the batteries will charge up for, say, 20 minutes at 100 milliamps, until they've reached a high enough state of charge to deliver an appreciable amount of energy to the cell phone. Then the cell phone will charge from the storage battery at, say, 250 milliamps (the actual charge current depends on how dead the cell phone's battery is) for ten minutes, and then with the storage battery depleted, shut charging off for the next twenty minutes until the storage batteries are charged again. In this way, we charge the cell phone at an acceptable charge current even though the solar cells can't put out enough power continuously.

An advantage of having a storage battery in the system is that you can leave the solar charger outside or in a window to collect energy during the day, and then charge your phone using that stored energy in the evening after the sun has set. This makes it possible to use the solar charger as your everyday cell phone charger, instead of being for emergency or off-the-grid use only.

Another advantage of having a storage battery is that it means the solar charger can function as a solar battery charger for AAA cells. This is useful if you're carrying, say, a digital camera that runs from AAA cells. If you needed AA batteries instead, use an AA battery holder in place of the AAA holder in the instructions.

The last nice thing about this system is that in an absolute emergency, say, after an alien invasion has blotted out the sun, you could replace the rechargeable NiMH batteries with disposable alkalines and charge your cell phone from them. In most circumstances you'd never need this capability, but if you have to contact the president regarding the aliens' one weakness, it might just save the planet.

Step 9: Hardware Part Deux: Components

Picture of Hardware Part Deux: Components

The charge controller is the heart of the system, and unfortunately is the only part that isn't an off-the-shelf product, so we're going to have to make one. Its not something that can be made from standard Radio Shack parts, because it runs at very low voltage and needs good precision. If you’re not feeling up to the task of making one after reading this section of the instructions, don’t despair. I made a few extra and have them in my etsy shop You could also order all the components in thru-hole variants and build the circuit on perf-board if you prefer. Just make sure to use 1% resistors.

The first step is to collect all the components. The following will be required:

PCB components (Parts express is a good source.)
Pre-sensitized single sided copper clad board, at least 1"? square
Developer for above
Ferric chloride
Small drill bit (1/32 or so)
Transparency film

Electronics: ( would be the standard place here.)
1 Op Amp MCP6002-I/SN-ND
1 Dual AAA battery holder with leads BC2AAAW-ND or Radio Shack
1 shottky diode MBR0540T1GOSCT-ND
1 zener diode 568-3779-1-ND
2 100k ohm 1% 0603 resistors
1 5k ohm 1% 0603 resistor
1 16.2k ohm 0603 resistor
1 3.9 ohm 1206 resistor
1 MOSFET FDS6898ACT-ND The MOSFET has to be fully turned on by 2v for this to work, so make sure if you're going to substitute
1 AnyVolt Micro universal DC-DC converter (, not available from digikey)
3 Powerfilm MP3-37
1 Charging plug for your cell phone or other device.
2 AAA NiMH batteries
t if you have to contact the president regarding the aliens' one weakness, it might just save the planet.

Step 10: Expose the PCB

Picture of Expose the PCB

Once you have all the parts collected, the first electronic step is to etch a circuit board with the attached artwork. This is a 600 DPI image and should print to about an inch by .75" There are lots of instructables and other internet instructions on how to etch circuit boards. The following is a brief overview

1. Print the artwork on transparency film.
2. Remove the black-out film from the copper clad board, and place the transparency film on top.
3. Press the transparency film down onto the copper clad board with a piece of glass or plexiglass. This is important for getting good definition.
4. Expose the board. 5 minutes at six inches away with a 60W desk lamp seems to work, but I prefer 90 seconds from a 500W halogen floodlight.

Step 11: Etch and Drill the PCB

Picture of Etch and Drill the PCB

Once you have the PCB developed, Place the board artwork up in a tank of ferric chloride. An hour with no heat or bubbling is about the right amount of time, but check it periodically. When it is done, wash it off with water, then expose it to light again with no mask and strip off the resist with developer. Sand or cut off the excess baterial, but leave 1/4" on one side. With a 1/32" drill bit, drill out the holes. Also, drill a sequence of holes in the excess space as shown. We'll be using this to sew the regulator to the pouch in a future step.

Step 12: Populate the PCB

Picture of Populate the PCB

Solder the components on according to the image. The left eight-leaded component in the image is the MCP6002 op amp, and the right eight-leaded component is the FDS6898A MOSFET. The resistors are, from left to right, 100k, 16.2k. 100k, 5k. The left diode is the Schottky and the right diode is the standard or zener diode.

There are a couple ways to solder surface mount components. One good option is to melt a blob of wire solder onto each solder pad, then with tweezers hold the component in place and with the iron wick the solder up to meet the component. A very fine tip and a temperature controlled soldering iron make this go a lot more smoothly. A better option is to use a syringe of solder paste to place paste on each pad, then heat the entire board with an air pencil or heat gun.

The circuit operates as a comparator circuit with hysteresis. If the output of the comparator is high, that turns on the FET, which turns on the AnyVolt Micro, which charges the cell phone from the storage battery.

If the output of the comparator is low, that turns the FET off, which turns off the regulator and stops the cell phone charging. This allows the solar cell to recharge the storage battery.

If the output of the comparator is high (cell charging ON) the comparator is looking for a battery voltage of 2.3V. It will stay on until the battery voltage falls below 2.3v, then turn off the cell phone charging. At this point, it starts looking for a voltage of 2.7v. When the solar cells have charged the battery to 2.7v, the charger turns on, and the cycle repeats. In normal operation with a phone connected, the battery voltage is always rising to 2.7, then falling to 2.3, then rising again. how long this takes depends on the amount of sunlight, but a 30 minute cycle seems typical.

The 3.9 ohm resistor limits the charge current, to prevent overloading the regulator or the phone.

Step 13: Connect Up the Charging System Components

Picture of Connect Up the Charging System Components

With the PCB fabricated and populated (or purchased from my etsy store) its time to connect all the charging system components. First, solder the AnyVolt Micro to the pads labeled Ro. Rg and Ri Ro connects to the Vout lead of the Anyvolt micro, Rg connects to Gnd and Ri connects to Vin.

Solder the battery holder to the board. The black battery holder wire connects to the pad labeled B-. The red lead connects to the pad next to that.

Examine the charging adapter you are sacrificing. Typically one of the wires will have a stripe marking the polarity. If there are no markings on either wire, mark one wire with white-out. If it is a round cable, typically the internal insulation will be color coded.

Cut the cable six to twelve inches from the end that plugs into the cell phone. Now, strip the insulation from the end that plugs into the wall or car, plug it in and with a multimeter, read the voltage, and note the polarity. This is what we’re going to be replicating with the solar charger, so it is very important to have it right. Having it wrong might let the magic smoke out of your cell phone, and that stuff is expensive. In my case, the charger puts out 5v, and the wire with the white stripe is positive.

Step 14: Adjust the Output

Picture of Adjust the Output

Next well be adjusting the solar charge controller to match the stock charger. Put a pair of fresh AAA batteries in the battery holder. Freshly charged rechargeable batteries would be my choice, but alkaline ones will work too. Now, measure the voltage between the two top pads as shown in the picture. It will likely read 8v or so. There is an adjusting screw on the side of the AnyVolt Micro. Turn this until the output reads 5v, or whatever your device is expecting. The adjustment screw is a 22 turn potentiometer, and you cannot damage it by turning it too far. You'll need to turn it at least several complete revolutions to get to the right range.

Once the output is correct, solder the charging plug wires to the board. The C+ output is positive, and the other similarly sized and shaped output in the top center of the board is negative. Check the output voltage again, because we're at a moment of truth. When you've verified it is the correct voltage and the correct polarity, plug in your cell phone. It should register that a charger is connected and start charging. This will be charging off the AAA batteries in the holder, so if you're using alkalines, unplug it after you verify that its correct. Otherwise the cell phone will charge off the alkaline batteries and then they'll be dead. That would be wasteful.

Solder two long thin wires from the remaining two pads (One is marked P-) as these will go to the solar cells. Conradulations, the electronics are basically done. Now we get Hybrid!

Step 15: Attach the Hardware to the Software

Picture of Attach the Hardware to the Software

Now its time to put everything together. The first step is to turn everything inside out, and sew the battery holder and regulator to one of the inside hems. This is done by hand, through the holes that we drilled in the battery box and controller. The seams are four layers of fabric and attach directly to the snaps, so they're strong enough to hold the weight of the battery and regulator. Then run two thin wires for the solar cells through the stitching that connects the zipper to the bag on the end with the attached battery box and controller assembly. This will bring these two wires under the hood which covers the zipper and outside the pouch.

Its also a good idea to sew the charger plug wires to the seam. This will keep some strain off of the joint on the PCB.

Step 16: Solder Together the Solar Array

Picture of Solder Together the Solar Array

Connect all three solar cells in parallel. The cells have silvered end tabs for connecting, but these are covered in plastic film. With your soldering iron, melt a small hole in the plastic film anywhere you need to solder a wire. The plastic film will melt, and then the tab will readily accept solder. Remember you're working on plastic and be careful not to use too much heat. Also place two solder dabs at the bottom of the cell assembly, to connect to the charger wires when the time comes. Using a multimeter, measure the polarity of the output of the solar cells, and note it. The polarity in the final pictures of this Instructable is correct, but its always a good idea to measure.

Step 17: Bond, Solar Cell Bond

Picture of Bond, Solar Cell Bond

Now we'll be bonding the solar cells to the pouch. Run a layer of Sil-Net around the outside edge of the bottom (silver side) of each cell. Insert a piece of cardboard into the pouch to make a flat, rigid surface, and then align and place the cells onto the top surface. It's a good idea to place the cells above the zipper pouch, because even though they're flexible for solar cells they're still stiff compared to the SilNylon.

When the Sil-Net attaching the cells has dried, test to make sure the solar cells are well attached. If they are, cut away the excess wire that runs to the regulator and solder the cells to the wire. Use more Sil-Net to secure the wires to the fabric - getting them snagged on something in the backcountry would be a very bad thing.

Step 18: Testint, Testing, 1,2,3

Picture of Testint, Testing, 1,2,3

You're done building! Now, its time to test. Measure the voltage of the pair of AAA NiMH batteries you will be using, then insert them into the battery box. Write down the initial voltage. Place the charger somewhere sunny with the solar cells facing the sun. Go have a snack and clean up the mess that you made. Come back in two or three hours, remove the batteries and measure the voltage again. The batteries should have a voltage .1 to .2 volts higher than they had before. If so, then the charger is working to charge its internal battery. If not, check all your connections and wires between the solar panel and the battery box.

Once the internal batteries are charging properly, let them charge in the sun until they reach 1.4 volts each. At this point, its time to test charging your cell phone. Plug the cell phone in, take a deep breath, and hear that reassuring Bloobloobeep that means it started charging. It'll probably show zero bars or one bar of charge - we're still not charging as fast as a wall adapter would, but this is okay.

If the internal batteries are charging from the solar cells, and the cell phone is charging from the internal battery, congratulations! You just made a solar charger! It takes about 10 hours to charge my phone, yours is likely to be similar unless its a smartphone of some sort.

It'd also be a good idea to test the waterproofness in your shower before taking it on a trip, in case you missed any seams, stitches or gaps.


Mase723 (author)2012-11-02

This is ideal for campers or travelers. I bought a high capacity solar charger and I was surprised how long it stores energy. The concept of a waterproof solar charger is new to me, do they convert less solar energy due to the protection from water? Thx. for this thoughtful post!

bigpunk81 (author)2011-10-29

VBT (TM) LOL!!! Made me chuckle, thank you Anti-Martha

KNEX BUILDING IS FUN (author)2009-04-20

how can i buy it the link doesnt work and also how much is it? There are many similar devices maybe you can find one useful for you,or you can go to amazon to have a look.

WayfinderAli (author)2010-07-07

hello?! anyone there? 1. how much were the solar panels? 2. what company did you buy them from? 3. how much did this project cost?

T8tersalid (author)2010-07-04

I'm going on a 7 day backpacking trip later this summer and needed a portable solar charger to charge my camera. Thanks you so much, this will help out a LOT!

WayfinderAli (author)2010-07-02

how much did this cost? I'm on a budget. and would you have to actually make the bag? I have mad sewing skills, but I would think that a seal line brand map bag would work well and maybe be more waterproof. how waterproof is it really? I'm a sea kayaking guide and this would be pretty awesome to charge on the deck of my boat. I run out of battery on my phone by the end of a 5 day trek.

deathpod (author)2010-02-14

This may be a stupid question, but how can I figure out how much current my phone needs to charge? I have a motorola with a 3.7v battery.

knektek (author)deathpod2010-05-03

Usb is always 5v. Or if not, check your wall wart to charge your phone. It will tell you the required output.

el_clutch (author)2010-01-12

 Was just wondering if the waterproof pouch affects the efficiency of the solar panel all that much is or is the loss negligible?

spike2fei (author)2009-09-30

can it be done for acid lead battery it will help me thaks

HADJISTYLLIS (author)2009-09-07

Can i use single op-amp because i don't have one of this?

tengaman (author)2009-08-01

love the ible you did great i have a question would it not just be easier to use the solar pack to charge some AA batteries and buy a little cell phone charger from walmart they run on 2 AA bateries and then just charge 2 AA batteries and put them in the them in the portable cell phone charger and bing bang boom done then just put it all away in your pouch when your done and yay your not lost in the wilderness

noreplyguy (author)2009-07-06

how mich is one and where can i get one!! :D:D great idea

jackie2992 (author)2009-06-15

Any chance on getting a premade circuit?

whyexactly (author)2009-04-09

I'm building one of these as a project for school, and one thing I noticed is that the AnyVolt Micro output cuts out when the input is dropped below 2.2V, which, if I'm not mistaken, means that you could work the whole setup down to a Schottky diode and the AnyVolt Micro as it would automatically cut off the batteries from outputting if they drop below 2.2V. I ahven't finished testing the AVM yet so I'm not 100% sure of this yet though.

One issue is the quiescent draw of the AnyVolt Micro - it'll run the battery down in dim light just staying on. The other thing the comparator circuit does for you is provides for burst charging - my cell phone turns the backlight on when it starts charging, which draws significant power. By storing up the energy then charging at a higher rate, then turning off to recharge the batteries, the amount of total power consumed by the phone's backlight is reduced. The comparator adds hysteresis, which is important with those limitations. Incedentally, since I wrote this Dimension came out with another regulator called LVBoost which is smaller, higher current, and can run down to .7v input, plus has significantly lower quiescent draw. You can get more juice out of the battery that way - like you say, the AVM cuts out at 2.2v, which works, but it only uses about half the capacity of the battery before cutting out to recharge. If I was doing this application today that's what I'd use.

Gotcha, I'd neglected the quiescent draw. I don't have the issue of the backlight coming on with my phone, but I added a USB port for my MP3 player, which does turn the screen on when it charges (I'm tempted to reconnect it's hold switch to the backlight to save power). Oh wow that would be sweet, although I think my instructor might get mad as we just spent a bunch of money ordering AVM's haha. I'll keep that in mind if I do a v2.0 though.

Fieldownage (author)2009-02-05

Oh dear, just wanted to inform that if you don't clean pcb's copper surface with steelwool(?(sorry I'm Finnish and don't know what's the word for that)) it may block the electricity.

junits15 (author)2008-11-05

where did u buy your solar panels?

lifelong-newbie (author)2008-08-25

Thought another stickler would have mentioned it:
Step 18 Testint Testing 1 2 3

Still a great ible

Sandisk1duo (author)2008-08-07

lol step one; Software

unitedelectric (author)2007-11-17

Wow. Cool project indeed. Is there any logic to adding a diode to protect from the battery draining through the solar cells in low light situations (ie battery voltage higher than panel voltage)?

yes yes yes. without the diode the current will run back into the panels. You are correct.

joe57005 (author)ShmemilyWoodey2008-08-03

Leaving the diode out could also damage the solar cells, not just drain the batteries.

mutantxgene (author)2008-06-09

I have a newbie question. Most of the diy solar projects I've seen you have to make sure that regulators diodes etc. are used and that you cut off one end of a phone charger and solder everything together. Instead of cutting off the wires from a charger, couldn't you just hook the solar cells directly to the charger? I figured that the charger has all of the necessary electronics already. I'm new to soldering and electronics so forgive my lack of knowledge.

You can snip the wires off a car cigarette adapter and then connect the cigarette adapter to your solar panels, and then use that to charge your phone. You are right. The adapter that normally connects to the car battery has regulators and diodes and all of that stuff included. It takes a 12 volt charge from the battery and converts it to 5volts so you can safely charge your phone.

Although, its probably a good idea to install a diode between the solar panels and the cigarette adapter because I have seen instances where cheap cell phone battery chargers still drain the battery of the cell phone even when they are plugged into a cigarette adapter when the car isn't running. Diodes are super cheap and easy to install, so it shouldn't be too difficult. The regulator IS the cigarette adapter that changes the voltage to a normal level for your cell phone.

The black box or end of the connector contains the transformer, diodes, and anything else that would prevent you from overcharging or damaging your battery pack.

abadfart (author)2008-06-14

nice but id use D cells and you can also use solar panels from old calculators

Saitam (author)2008-04-20

"The last nice thing about this system is that in an absolute emergency, say, after an alien invasion has blotted out the sun, you could replace the rechargeable NiMH batteries with disposable alkalines and charge your cell phone from them. In most circumstances you'd never need this capability, but if you have to contact the president regarding the aliens' one weakness, it might just save the planet.

Thanx for the instruction i had in plans to make a exactly similar last summer but now it will be finished'

Elorrum (author)2007-08-09

has anyone got a plan/design to use the small panels from solar garden lights to make a larger panel that could charge a 12V battery? I got about 30 lights that I want to caniblaize the panels out of and make something larger. thanks.

computerwiz_222 (author)Elorrum2007-12-15

It is doable, you could probably follow the instructions from makezine, their actual magazine had an article in it on using salvaged solar panels. If you want to get any significant source of charge though, you will need a large and efficient panel. I went to Canadian Tire and bought an 80 dollar solar panel which outputs 12 volts @ 400ma in direct sunlight. It works great, but to charge a 7ah battery, it takes like 2 days. Those little panels *might* squeak 400ma.

What I did was plug the panel into one of those car booster packs, let it charge all day, go to work... whatever. Then when I got home, I would run my laptop off of the charged booster pack through an inverter. (stay off my case about the waste of time going from DC-AC-DC, i know, this was an experiment) It worked great! The only thing i didn't do was charge the laptop off of the booster pack or run it at full CPU. These two things would kill the booster pack very fast! The booster pack usually died almost fully, I could have extended this charge by bypassing the extra step (DC-AC-DC). I was up north working and this was a little experiment I did to stop myself from going nuts with boredom... (no soldering for 2 MONTHS!)

Tobita (author)Elorrum2007-12-10

i guess it is possible, but there might be a problem with all the wiring

denilsonsa (author)2007-12-07

Nice idea. I wonder how to mod this project so that i can supply energy to a microcontroller. Then, I would be able to make some nice projects to put at sunlight with no need for external power. (but, then... I guess the batteries and the electronic components should not be exposed to direct sunlight)

lindsclou (author)2007-08-16

Sorry... didn't finish reading some of the posts already made! But I see where someone asked the same question, so I got my answer there! Thanks!

lindsclou (author)2007-08-16

This is definitely a cool project! I'm not very tech savvy so this question might seem a little weird... but I'm assuming I can use the same concept to make one to plug in small kitchen appliances, etc.? Would I need to change anything about the design other than the bag? (don't think it is neccesary to put a toaster in a bag LOL). And a kinda off the subject question... does anyone know where I can find an instructable on making my own enclosed compost tumbler out of recyclables?

Mesarose777 (author)2007-07-21

Hi, Sounds great! How would you go about making one large enough (powerful enough) to run the new portable Microwaves to take aboard a boat? Or to run a small fan or toaster for fancier camping? Or to run a computer and a lamp during a power outage? Seriously, you have a great idea.

pekar (author)Mesarose7772007-07-21
-describes considerations in designing a system of similar size/use.

Hi, Well, the basic idea would be the same, but a microwave is serious power, at least a couple hundred watts. This project is running at most a solar charge power of .45W and 1.5W to the cell phone. That would be a scale-up of 100 times or more in terms of power. This would necessitate different components and construction techniques. Also, this project only turns the charger on when the battery is ready, which might be any time between "now" and "an hour from now" depending on the sun and the state of charge of the battery. That's necessary for cell phone charging, but a bit annoying when you want breakfast. With a larger system you'd need a much larger solar panel, of course. Something rated to charge a 12V battery would be ideal. You'd need bigger batteries, a 12v lead acid deep cycle battery would be the usual route. Really the application is different enough that it'd be a new instructable.

Leroy (author)2007-07-21

What a great idea to use an intermediate storage battery so you can save the solar energy! How much does this device weigh? Have you hiked with it? If so, how well does it work? Approximately how much did it cost for parts? I love your idea too. It looks like a great project for anybody who has a cell phone and likes to get off the beaten path for a few hours or a few days. Plus, it could be an essential piece of backpacking equipment for a life-saving emergency. Thank you for taking time to make such an awesome instructable!

fabiusX (author)2007-07-21

One of the best instructables ever. Not easy to do for common people but extremely well explained.

blondietheblond (author)fabiusX2007-07-21


theprofessor (author)2007-07-21

My only comments are that you could build your own dc/dc converter and charge controller, another comment is that your current scheme that when sunlight is low, the charge controller is going to suck energy from the batteries. if I could make a small suggestion, there is a Micro M+ charger which is commercial available, but if you can get you hands on an October 1999 QST its fully detailed how its implemented, that is a good starting point, while i don't think you care about low RF noise and the p-channel mosfet is not needed, some of the other schemes there can be used here. Also I would recommend being a little more careful with your solder job, use a little less or get a finer multicore solder, any solder touching a component case is considered a defect in the manufacturing world under any class of JSTD001D also surface mount diodes typically cost 2-3x what their leaded companions cost, you can take a leaded diode and surface mount it quite easily and save yourself a few bucks.

Hey, thanks for the feedback. It'd be a simple enough matter for someone following this instructable to build a different DC-DC converter if they were feeling ambitious. I had the AnyVolt Micro in my parts box. The diodes were also parts box, reasonable substitutions would work. The charge controller does draw energy from the battery in the "off" state, but the quiescent draw of the op amp is .17mA and the typical loss from the resistor network is about .12 milliamps. That's well below the self-discharge rate of even an excellent NiMH battery, so I wasn't too worried about it.

fimjox (author)2007-07-21

When backpacking and such, you should always always turn off your cellphone when not in use. Especially if you are out of range, (which you probably were 27 miles is far ) When you are out of range the cellphone is not on standby but it is constantly trying to connect to a system that does not exist, which kills the battery real quick. . There is no use in a cellphone that can't connect anyway. Penguins know this.


SacTownSue (author)2007-07-19

I love this project. I have too much going on right now, but will probably do this someday. Thanks.

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