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"Finally, A Proper Solar Charger For Hikers And Bikers" - Cult of Mac

Can a compact solar USB charger charge a phone and an external battery at the same time in about 3 hours? Yes! This is an Open Source Hardware instruction manual on how to build the Solarpad Kit solar USB charger, which includes the Solarpad solar panel and Power Core USB battery.

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Why Open Source Hardware?

The solar USB charging market has become saturated with low-quality and poor performing products and every year the big companies are selling the same products with very little improvement. Therefore, Solarcycle has developed its open source solar USB charger to empower customers with the ability to build their own solar USB chargers and to prove that a better solar charger that outperforms anything else on the market is possible.3-D files, Gerber files, schematics, and part drawings can be downloaded from www.solarcyclepower.com

This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

What's Special About Solarpad?

Our Solarpad Kit sets a new standard for a rugged, lightweight, compact, powerful, water resistant, and easy-to-use USB solar charger that can keep a smart phone charged all day! Connect Solarpad to the Power Core battery input then use the cable that came with your smart phone and plug it in to the Power Core output. Solar charge the Power Core battery and charge your phone from this battery at the same time! We designed the Solarpad Kit without an on/off button so you just plug it in and it works automatically! If a phone has a unique connector, one end of its charge cable always has a standard USB compatible plug. No extra cables are required because they are built-in. Use the Solarpad Kit on your next adventure! Will not leave you powerless.

The Solarpad Kit is designed to outlive the life of your Smart Phone! Solarpad uses a high-quality, custom Suntactics solar panel, which has a fluoropolymer film with the best light transmission, precision cut and tabbed high-efficiency solar cells, and a high-strength substrate. The panel is attached to a housing, which holds the buckle straps and 1/4-20 tripod thread in place. Our Power Core battery uses a high-efficiency, high-power charge controller from Maxim and the housing is sealed with high-strength epoxy, which prevents water from leaking in. Also, Power Core uses the same battery that's used in the Tesla electric car, which is the best battery of its kind. Even the built-in USB cables consist of thicker gage wire, which allows the electricity to flow more efficiently. The Solarpad Kit is engineered to squeeze the most energy possible from the sun's rays in to your smart phone. No short-cuts that compromise power or efficiency are taken, period.

Solarpad Solar Panel Specs:
* Size: W 6.5 inches X L 10.9 inches X H 0.6 inches

* Strap Material: Polypropylene * Strap Length: 1.5 Feet

* Fastener Style: Plastic Side Release Buckle

* Cable Length: 10.0 inches * Weight: 270g (9.52 oz)

* Body Material: Plastic

* Output - Female USB 2.0 Type A Connector

* Nominal Output - Current: 1000mA | Voltage: 5 Volts

* Max Open Circuit Voltage: 6 Volts

* Cell Type: Monocrystalline * Cell Efficiency: 18.8%

* Compatible with Power Core Battery Only

Power Core USB Battery Specs:
* Time to Fully Charge Power Core @ 5V 1A: 3 hours

* Capacity: 3350mAh/3.6V * Type: 18650 Lithium-Ion

* Diameter: 1.2 inches * Body Length: 4.2 inches

* Cable Length: 7.0 inches * Weight: 100g (3.53 oz)

* Input - Male USB 2.0 Type A Connector

* Input - Current: 450 to 1300mA | Voltage: 5 to 6 Volts

* Output - Female USB 2.0 Type A Connector

* Output - Current: 500mA | Voltage: 5 Volts

* Body Material: Aluminum Tube with Plastic Caps

* Battery Life Under Typical Use: 5 years

* Provides up to 140% iPhone Charge or 70% Galaxy S4 Charge

* Compatible with iPhone, Android, Windows Phone, and Others

Circuit Efficiency So Far: By dividing the # iPhone charges by the ratio of Power Core rated capacity to iPhone rated capacity [1.4/(3350/1448)], the total system efficiency is roughly about 61%, which means about 61% of the energy coming from the stored energy in Power Core reaches your phone's battery. Keep in mind that the energy is going through many regulation circuits inside Power Core and inside your phone, so energy is lost at each regulation step before reaching the phone's battery. These tests were done with the phone on and the screen off, so maybe a better calculation is with the phone shut down. Further tests by verifying battery capacity and charge current with current meter data loggers and taking the integral of the data curves will make this calculation more accurate. Also, refinement of the circuit and better heat management can lead to improved efficiency ratings. However, even at 61% efficiency, Power Core still performs better than any battery of similar size on the market.

This Instructable is broken down into 9 sections:

  1. Materials, Tools, and Files Required
  2. Solarpad Assembly
  3. Power Core Battery Assembly
  4. Power Core Cable Assembly
  5. Epoxy Stage
  6. Power Core Final Test (How the Circuit Works)
  7. Power Core Final Assembly
  8. Solarpad Kit Final Assembly
  9. Safety and Troubleshooting

*WARNING: Be careful when handling any Lithium-Ion battery because shorting the battery can cause burns. Always wear safety goggles. Please use recommended battery and circuit components because of the higher 2000mA max battery charge current involved.

FCC Compliance: NOT Required because the circuit frequencies are below 1.7MHz

Estimated Completion Time: 2 to 3 hours

Step 1: Materials, Tools, and Files Required

Here is a list of the materials, tools, and files required. Links to purchase or download most items are provided. The items in the Solarcycle Shapeways shop can be downloaded for free or purchased directly and are marked up as follows: $1 mark-up for small components, $2 for medium components, and $5 for large components. Mark-up funds will go toward maintaining the Solarcycle site and improving solar charger technology. Shapeways tends to have very good quality 3-D printing in all sorts of colors and materials. Results may vary with other 3-D printing methods. 3-D files, Gerber files, schematics, and part drawings can be downloaded from www.solarcyclepower.com

MATERIALS:

QTY Description

1 Solarpad Bracket http://www.shapeways.com/shops/Solarcycle

2 Solarpad Edge Trim http://www.shapeways.com/shops/Solarcycle

1 Solar Panel (Layout Drawings can be downloaded at http://www.solarcyclepower.com/index/Open_Source.h... Suntactics solar panels are recommended because they have the highest verified power output. You can try to cut your own solar cells using this instructable https://www.instructables.com/id/Ultra-Portable-Dre... or you can contact www.suntactics.com to build one for you. You may have to supply some materials to Suntactics for a few prototypes because they are not off-the-shelf products yet.)

1 Stainless Steel 1/4-20 Nut (The thinner nut height the better http://www.mcmaster.com/#stainless-steel-hex-nuts/...)

2 1.5' long polypropylene 1 inch wide strap (Make sure they when you cut the straps, you melt the ends to prevent fraying. Use 2 extra straps for extensions to wrap around larger cargo like backpacks or tent bags. You can also make longer straps http://www.acehardware.com/product/index.jsp?produ...)

2 1" Plastic side release strap buckle set (Use 2 extra buckles for extensions to wrap around larger cargo like backpacks or tent bags. Available at Ace Hardware. Reference http://www.bulkstrap.com/plastic-hardware.php)

1 Power Core End Cap http://www.shapeways.com/shops/Solarcycle

1 Power Core Cap Shroud http://www.shapeways.com/shops/Solarcycle

1 Power Core LED Cap http://www.shapeways.com/shops/Solarcycle

1 Power Core Circuit (Schematic, Gerber Files, etc. can be downloaded at http://www.solarcyclepower.com/index/Open_Source.h... Some can be purchased on Ebay http://www.ebay.com/itm/271412305343?ssPageName=ST... The main IC components are the Maxim MAX8903G charge controller and MAX1790 DC-DC step-up converter circuits)

1 NCR18650B 3350mAh Unprotected Panasonic Lithium Ion Battery www.ebay.com (If lower cost is necessary, try the Panasonic NCR18650A battery with a slightly less capacity of 3070mAh. Make sure it's unprotected and check the battery part number carefully. Protected batteries have added length with a built-in circuit, which may affect performance. Reference http://industrial.panasonic.com/www-cgi/jvcr13pz.c... Other brands of batteries are NOT recommended because the charge controller current to the battery can be as high as 2000mA and the Panasonic NCR18650 chemistry can handle it. If you need to use other brands, make sure that they meet the same specifications, chemistry, and can handle up to 2Amps of charge current. Using batteries that don't meet these specifications can lead to dangerous battery damage.)

1 Green 5mm Straw Hat LED www.ebay.com

2 Hirose 2-pin connector DF3-2S-2C http://www.digikey.com/product-detail/en/DF3-2S-2C...

2 Hirose 4-pin connector DF3-4S-2C http://www.digikey.com/product-detail/en/DF3-4S-2C...

10 Hirose Socket 24-28 AWG Crimp Pin DF3-2428SCC http://www.digikey.com/product-detail/en/DF3-2428S...

2 2.3mm X 60mm (.09" X 2.5") Cable Tie http://www.centralcomputers.com/catalog/product.js...

2 3' USB Male-Female USB 2.0 Type A Extension Cable (Cable drawing can be downloaded at http://www.solarcyclepower.com/index/Open_Source.h... Ever Red cables have good water resistance. Some are sold on Ebay http://www.ebay.com/itm/271412290808?ssPageName=ST...)

1 12" Rip Tie Lite http://www.frys.com/product/937708?site=sr:SEARCH:...

1 Aluminum tube 4.19" Long (Cutting the tube to size with a hacksaw and filing the end seems to work best. Pipe cutters tend to crush the tube. Anodize optional, fine sandpaper hand polish works good too http://www.mcmaster.com/#89965k631/=qu57q8)

1 1" Wide Kapton Tape Roll http://www.mcmaster.com/#7648a715/=qu5807

2 1" Kapton Tape Disc http://www.mcmaster.com/#77595a35/=qu586k

1 1" Dia Piece of Heat Shrink Tubing 2.7" Long http://www.frys.com/product/3222501?site=sr:SEARCH...

2 1/16" Piece of Heat Shrink Tubing 1.0" Long http://www.frys.com/product/3221391?site=sr:SEARCH...

1 1.7oz (50mL) 3M Sotch-Weld Dp-100 Plus Clear Epoxy http://www.grainger.com/search?searchQuery=dp-100+...

1 Roll of solder wire

6 Aluminum 1/8" POP Rivets .126"-.187" Mat'l Thk http://www.mcmaster.com/#97447a020/=qu7adi

2 Epoxy Mixing Nozzles (Epoxy may harden in nozzle so have spares just in case http://www.mcmaster.com/#catalog/120/3413/=qu7buz)

Various Lengths 26 AWG Standard Red and Black Stranded 4 Amp Max Wire Listed Below: http://www.mcmaster.com/#catalog/119/798/=qu7rf6

1 .96" Red Wire .06 strip one end .20 strip the other end

1 8.00" Red Wire .06 strip one end .20 strip the other end

1 1.06" Black Wire .06 strip one end .20 strip the other end

1 6.10" Black Wire .06 strip one end .20 strip the other end

TOOLS:

QTY Description

1 Power Core Battery Fixture https://www.shapeways.com/shops/Solarcycle

1 3M Manual Epoxy Applicator Gun EPX (I think they are changing the gun to a metal design but I found a plastic version here http://www.uline.com/Product/Detail/H-3803/Adhesiv...)

1 Wire Strippers 24-26 gage range

1 Wire Crimper 20-24 gage range

2 Quick Grip Clamps able to open at least 6 inches

1 POP Rivet Gun (I used PowerLink 30 and it seems hard to find online, but I'm sure any POP rivet gun will work)

1 Tape Measure (Precision Calipers recommended for scribing cuts)

1 Third Hand Soldering Clamp

1 Soldering Iron

1 Heat Gun

1 Multimeter

1 Piece of Rubber .6" Dia. X .3" H

1 Scissors

Step 2: Solarpad Assembly

If the solar panel doesn't come with 6 holes that line up with the plastic edge trim and body, you can make the holes by inserting the trim in to the body slots, clamping the solar panel to them and drilling out the holes with a 1/8" drill bit. These will be the holes for the rivets during final assembly.

Cut one of the USB cables 21" from the male end. Strip the outer jacket .5" from the end, remove the shielding, and strip the Black and Red wires about .25" from the end. Cut away the Green and White wires because they aren't needed.

The back of the panel should have two leads. To verify the polarity, just attach a Volt meter to the leads and shine a light on the panel. Positive voltage means that the positive and negative leads are in the correct orientation. (I've had a panel with reversed orientation, so it is always good to check before soldering)

Bend the leads to the side and place Kapton tape on top of the exposed leads that are not being soldered to. This protects exposed leads from moisture. You can also apply epoxy to them, but it would take more time. (Having the USB cable come out from the side creates a service loop within the plastic body giving it a retractable cord effect)

Solder the USB Red wire to the positive lead and the Black wire to the negative lead. Push the leads down to be flat as possible. (When the panel is attached to the plastic body during final assembly, you don't want the epoxy on the leads to hit the 1/4-20 nut)

Build a Kapton tape wall around the soldered leads and cable with about a .25" gap around the leads. This wall will contain the epoxy, which acts as a water sealant and cable strain relief. Make sure some of the cable jacket is within the Kapton wall to make a good strain relief.

Place the 1/4-20 nut inside the plastic body on top of the large hole in the center. Build a Kapton wall around the nut with about a .25" gap and don't let the tape touch the nut. Be sure to center the nut on the hole.

For now, set aside these parts until the Epoxy Stage.

Step 3: Power Core Battery Assembly

Insert the NCR18650B battery in to the Power Core Battery Fixture with the positive side facing up. The fixture will align the Red and Black wires as you solder. Do not touch the soldering iron to the fixture because it can melt. You might be able to solder the battery without the fixture, but it is much harder and you would still need something to keep the battery from falling over. The fixture can be used for other battery projects too.

Place the .20" stripped end of the long Red wire in the trench labeled +RED and solder the Red wire to the battery. Try to solder to the battery quickly because too much heat to the battery may damage it. If there is any solder sticking out, smooth it out with the soldering iron.

After soldering, tilt the fixture and push the battery out from underneath with your finger. Turn the battery upside down and insert the battery in to the fixture with the Red Wire in the +RED trough and the negative end of the battery facing up. Crimp the end of the Red wire with the Hirose Pin and insert the pin in to port 1 of the Hirose 2-Pin connector. You want to attach the connector at this point because it is dangerous to leave a dangling bare end of a battery wire exposed and can potentially cause a short or burns if it touches the negative end of the battery.

Place the .20" stripped end of the long Black wire in the trench labeled -BLK and solder the Black wire to the battery. The negative end of this battery usually requires more heat to solder because there's more surface area in contact with the mass of the battery, but try to solder quick. If there is any solder sticking out, smooth it out with the soldering iron.

After soldering, crimp the end of the Black wire with the Hirose Pin and insert the pin in to port 2 of the Hirose 2-Pin connector. Tilt the fixture and push the battery out from underneath with your finger.

Bend the black wire straight down over the edge of the negative end of the battery and guide the red wire to loop around along the side of the battery. The effect should be that the Red wire coming down from the positive end of the battery is 120º apart from where the Black and Red wires meet. This wire geometry allows for the positive and negative wires to come out from the same side and gives the snug fit inside the aluminum tube without any glue.

Wrap a piece of 1" wide Kapton tape once around the middle of the battery to hold the wires down. Place a 1" Kapton tape disc at each end of the battery and fold the edges over the side of the battery. Then slide the 1" Heat Shrink Tube over the battery with the tube flush with the positive end of the battery. All the tube slack should be sticking out the negative end. Now use a heat gun to shrink the tube to complete the battery assembly.

Step 4: Power Core Cable Assembly

USB CABLE

Cut the USB cable with the male end 8.25" long. Take the Female end and line it up with the male connector and cut it to match (about 7.75" long). Strip .5" of the outer jacket and shielding of both ends and cut away the Green and White wires on the male end as they are not needed. Crimp the Hirose Pins on to the 6 wires.

Slide the Power Core LED Cap Shroud over the two cables then insert the wires through the Power Core LED Cap with the Male end through the top right hole. Then add the Cable Ties to the very end of the cable jacket to prevent the cable from sliding out.

Connect the Hirose 4-Pin connectors to the cables as indicated below:

Male cable - Red Wire pin to port 2, Black Wire pin to port 1

Female cable - Red Wire pin to port 1, White Wire pin to port 2, Green Wire pin to port 3, Black Wire pin to port 4

Tighten the cable ties and cut the excess slack. Pull the cables so the cable ties lay in the pockets of the LED Cap.

Attach the Power Core Circuit to the cable connectors as indicated below:

Male cable - connect to port labeled IN6V

Female cable - connect to port labeled USBOUT

Give the circuit a little twist to tighten the gap between the circuit and the LED Cap.

LED CABLE

Solder the .20" stripped end of the short black wire to the short leg of the LED (cathode) and solder the .20" stripped end of the short red wire to the longer leg of the LED (anode). Slide the 1/16" heat shrink tube over the LED legs and use a heat gun to shrink the tube. Crimp the Hirose pin to the ends of the wires. Attach the Hirose 2-Pin connector with the Red Wire to port 2 and the Black Wire to port 1.

Step 5: Epoxy Stage

Attach the mixing nozzle to the applicator gun. Ideally you want to use an applicator gun for this step to get in to the tight spaces. It may be possible to do it without an applicator gun, but it might take a longer time and be more messy. Either way, be sure to have a few sheets of plastic to do work over and to rest the epoxy applicator down on to catch any epoxy spills. This epoxy has a working time of only 5 minutes and hardens quickly, which is why all the parts are prepared for epoxy first. Try to keep the epoxy flowing in the nozzle or it will harden inside prematurely and you have to replace the nozzle. As it hardens, the epoxy does get hot, which is a normal exothermic reaction. If epoxy spills on something, be sure to clean it up right away before it hardens. Also, epoxy can give off a strong odor so be sure to work in a ventilated area.

Fill the Kapton walls with epoxy so that it barely covers the wires and just up to the 1/4-20 nut.

Fill the LED Cap pockets with epoxy making sure the tie wraps are in the pocket. (A cardboard box with a thin cut groove works well for holding the cables in place.)

Put a bead of epoxy all around one end of the aluminum tube and slide the Power Core Cap on while twisting the cap at the same time. Twisting the cap allows the epoxy to evenly spread out and you should end up with a nice bead around the cap. This visible bead ensures that the water seal is good.

Remove the Kapton tape walls while the epoxy is still rubbery and you should be left with a good epoxy encapsulation. Check that no bare wires are exposed and that the 1/4-20 nut is secure. If you think the solar panel cable needs more strain relief you can add some more epoxy on the cable jacket.

Remove the mixing nozzle from the applicator and put the cap on the tube or it could seal the epoxy inside the tube.

After 10 minutes the epoxy should harden, but may still be tacky and rubbery so don't touch the epoxy. At this stage, place the solar panel on top of the bracket to make sure that the epoxy globs don't interfere with each other. If they do, you can trim excess epoxy away with a knife. (To get the retractable cable effect, make sure the cable coming out from the solar panel is facing away from the slit in the middle of one edge of the bracket. The cable should loop around inside the bracket creating a service loop)

Step 6: Power Core Final Test (How the Circuit Works)

It's a good idea to test the circuit at this point before final assembly. If something doesn't seem to work you can use a multimeter to make sure that cable pins and batteries are connected properly.

Connect the battery cable to the port labeled BAT on the circuit. Connect the LED cable to the port labeled LED and bend it toward the LED Cap. Plug the male cable in to any USB port and make sure that the LED turns on. Now connect your phone to the Female cable with your phone charge cable and both the Power Core and your phone should charge at the same time. Disconnect and reconnect the Power Core male cable from the USB port a few times to simulate a shadow on a solar panel and your phone should keep charging, but the Power Core LED should turn on and off. If it works, continue to the next step.

(HOW THE CIRCUIT WORKS: This Maxim chip uses Smart Selector Technology, which passes and regulates solar energy directly to your phone as a priority and stores excess energy to Power Core with up to 2000mA going through the circuit. When the solar energy decreases, Smart Selector Technology instantly uses power stored in Power Core to compensate for any loss in solar energy to keep your phone charging. A dead Lithium-Ion battery goes in to a trickle charge mode, which takes about 15 minutes to recover from and is frustrating to wait for while camping or biking. Power Core solves this trickle charge mode problem by connecting the data wires on the Female cable to a voltage divider circuit that limits the charge current to an iPhone phone to around 500mA and an Android phone to about 700mA. The best explanation I found for the iPhone voltage divider circuit is here http://hackaday.com/2010/08/03/reverse-engineering...

You can also download the schematic and see the voltage divider circuit I used from www.solarcyclepower.comThis ensures that there is equal or more energy going in to Power Core than out while solar charging, which allows for charging in non-ideal conditions and prevents a dead Power Core battery from occurring. iPhones charge at 500mA and Android phones seem to charge at around 700mA with this circuit. This may seem counterintuitive, but doubling the charge current to your phone only reduces the phone's charge time by 1/3 because the charge rate is only increased between the 30% and 80% charge region. This is true for any Lithium-Ion charge controller because lower current at the beginning and end of the charge cycle is mandatory to prevent battery damage. Therefore, 500mA is a good compromise to keep a constant steady charge all day and 3 hours for 100% iPhone solar charge is still better than any other product of similar size today. You're essentially charging two devices, Power Core and your phone, at the same time so intelligent power management like this form a limited solar energy source is critical for maximum efficiency.)

Disconnect the battery from the Power Core Circuit. Insert the battery in to the aluminum tube. It should be a snug fit, but if it's too tight, try using a heat gun to make sure the heat shrink tube is fully shrunk. If it's still too tight, you can warm up the aluminum tube a bit with the heat gun. When the battery is inside the tube, push it to the bottom with a small piece of rubber and a plastic rod (The rubber protects the positive battery terminal from being crushed. I used the end of marker pen to push the rubber).

Fit check the entire Power Core assembly. Reconnect the battery to the Power Core Circuit. Insert the circuit into the tube making sure that the battery cable loops over the circuit creating a service loop effect. When you push the circuit in, twist it counter-clockwise so that the battery cable coils around as you push the circuit in, which takes up less space. Push the circuit in until the LED Cap touches the aluminum tube. If the LED Cap doesn't close all the way, check to make sure the battery cable is coiling up properly and not getting tangled or crushed.

Step 7: Power Core Battery Assembly

Attach a new mixing nozzle to the applicator. Once the fit check is complete, epoxy seal the LED cap by putting a bead of epoxy all around the LED Cap end. Push the LED Cap in and then put another bead of epoxy around the aluminum tube end. Slide the LED Cap Shroud over the aluminum tube while twisting the shroud. Twisting the cap allows the epoxy to evenly spread out and you should end up with a nice bead around the cap. This visible bead ensures that the water seal is good.

Turn the Power Core so that the cables are facing down and use the two clamps to compress the Power Core even from both sides. You only need about 5 lbs of clamping force so don't clamp too tight or the cap may distort. Make sure the clamps are resting straight up because if they are tilted, the epoxy may spill to the side. You can also do this step with your bare hands by squeezing it for about 5 to 10 minutes, but be sure not to touch the epoxy.

After 10 minutes the epoxy should harden, but may still be tacky and rubbery so don't touch the epoxy. Finish the Power Core assembly by attaching the Rip Tie to the female cable and use it to hold the cables against the aluminum tube.

Step 8: Solarpad Kit Final Assembly

Place the solar panel on top of the bracket with the cable looping inside to create a service loop. Attach the side trim pieces and insert the rivets in to the 6 holes. While squeezing the trim, bracket and solar panel together, use the POP rivet gun to compress the rivets securely. Even though the cable is securely epoxied to the solar panel, do not pull the cable too hard or it may bend the cable inside and wear out over time.

Turn the panel over and install the straps through the 4 slots in the back and attach the buckles in the arrangement shown in the photo. This alternating arrangement allows the straps to be connected both vertically and horizontally. For larger cargo, add extension straps with another set of buckles or you could cut longer straps.

Attach Power Core to Solarpad and you have completed the Solarpad Kit! Test it out by putting it in the sun, plugging in your phone, and blocking the panel to turn the LED on and off making sure that your phone gets a continuous charge. Enjoy independent power on your next outdoor adventure!

CONGRATULATIONS!

Attached is a photo of what a Power Core would look like with white cables, white caps, and a hand polished aluminum tube. Dirt is more noticeable on white though. Also, attached is an image showing many other uses for Power Core.

Here are some other Solarpad DIY projects that you can try:

https://www.instructables.com/id/Solar-and-Dynamo-B...

https://www.instructables.com/id/Solar-Powered-Sold...

https://www.instructables.com/id/Low-Budget-Tron-Co...

Safety and Troubleshooting on Next Page --->

Step 9: Safety and Troubleshooting

SAFETY

Do Not connect Solarpad directly to a Smart Phone. Solarpad outputs up to 6 Volts of raw unregulated solar power that may not be compatible with Smart Phones. Only connect Solarpad to Power Core.

Do Not leave Power Core or your phone in direct sunlight. Keep them covered or in the shade. The USB cables allow Power Core to be connected to Solarpad while being hidden away from direct sunlight. Some competitor solar products have a built-in battery that is permanently attached to the solar panel itself, but heat from the solar panel can cause the charge circuit and battery to get very hot, stop charging, degrade the battery, and shorten its lifespan.

Modifying: Never attempt to repair or modify the Solarpad Kit yourself. The Solarpad Kit does not contain any user-serviceable parts. Disassembling the Solarpad Kit may cause damage.

Acceptable Temperatures: The Solarpad Kit is designed to be operated in temperatures between 0º and 45º C (32º and 149º F). For best results, fully charge Power Core before traveling.

Keep USB Connectors Dry: If the USB connectors get wet, dry them off. They are water-resistant, but the metal USB connectors may rust with long exposure to moisture. Shake and blow out moisture inside the connector.

Storage: Store the Solarpad Kit in room temperature. Power Core should be recharged about once a year to prevent over discharge.

TROUBLESHOOTING

I left the Solarpad Kit outside and it didn't charge my phone:

1) Trees, mountains, and buildings may block the sun as it moves through the sky, which dramatically reduces power output. Placement and angle of the Solarpad is very important for phone charging. Luckily, smart phone Apps like these can help predict the sun's path using augmented reality through your phone's camera so you can see where the least obstructed position and angle will be throughout the day:
www.sunsurveyor.com

www.ozpda.com/sunseeker_iphone.php
www.solmetric.com/solmetric-isv-iphone-app.html

2) While a few clouds or thin hazy clouds will still work for solar charging, thick dense clouds won't. If it's a very cloudy day, Power Core may still charge, but wait until there is a break in the clouds to start solar charging your phone.

3) Hiking through a dense forest or mountainous area with the Solarpad Kit on your backpack may not be suitable for phone charging because there may be too many shadows reducing solar power significantly. Power Core may still charge, but wait until there is a clearing in the woods or a flat area to start solar charging your phone.

4) Charging very early in the morning or very late in the afternoon may still charge Power Core, but they are the weakest times for solar charging your phone because the sun is very low in the sky and Earth's atmosphere absorbs a lot more light. The sun is strongest in the summer from 8am to 4pm and in the winter from 10am to 2pm. Try charging your phone around these times.

5) If Solarpad surface is very dirty, it can significantly reduce the power output to your phone. Power Core may still charge, but try cleaning the Solarpad surface before solar charging your phone.

6) Make sure Power Core has about 15 minutes of solar charge before plugging your phone in to the Power Core. This will ensure that the battery has enough energy to compensate for brief power fluctuations and keep your phone charging.

Power Core LED doesn't light up when solar charging:

1) This can occur if Power Core is completely drained and goes in to a trickle charge mode. Solar charge Power Core for about 15 minutes and the LED charge light should turn back on.

2) Sometimes on extremely hot days, the surrounding hot ground and air will cause the Power Core circuit to shut off and stop charging even if it's in the shade. Put the Solarpad Kit somewhere away from the sun, like indoors or in a tent, to cool down and when you feel it is cool, take the Solarpad Kit outside to charge again with Power Core in the shade and elevated above the hot ground, like on a piece of wood. If there is not much shade, putting a small towel, cloth bag, or box around Power Core may also help it keep cool.

My phone still isn't charging:

1) Thinner USB charge cables have a history of not lasting very long. Charge cable damage can be visible, but sometimes it is not. Try replacing your phone's charge cable.

2) After a few years of use, the battery inside the phone tends to wear out and perform poorly. If your phone's battery has trouble holding a charge or runs out of power faster than usual, try replacing your phone's battery.

Power Core LED doesn't light up when charging from my USB wall adapter:

1)Thinner USB charge cables have a history of not lasting very long. Charge cable damage can be visible, but sometimes it is not. Try replacing your phone's charge cable.

2) USB wall adapters have a history of not lasting very long. Try another USB port or replace the wall adapter.

Power Core LED doesn't light up when charging from my laptop:

1) This can occur if Power Core is completely drained and goes in to a trickle charge mode. Keep Power Core plugged in for about 15 minutes and the LED charge light should turn back on.

2) Some older laptops have a low current limitation in their USB ports and will disable the USB port if the current exceeds the limit. Try plugging Power Core in to another USB port.

<p>The Kickstarter project for this was just launched. You can visit the page here: </p><p><a href="https://www.kickstarter.com/projects/249225636/solarpad-ultra-lightweight-usb-solar-charging-syst" rel="nofollow">https://www.kickstarter.com/projects/249225636/sol...</a></p>
<p>Thank you for your Instructable</p><p>Nice job.</p><p>Rima</p>
<p>Does it make more sense to connect the solarpad to the power-controller by something other than USB? It's sort of expected USB will be 5v</p>
<p>Question. I also built a solar charger from a Car USB charger. Could not get the chargers LED to light up on a 6v 1 watt Solar panel. Tested the output on the panel to 6.3 Volts.. I was able to use a 9v battery to get it to work. I was also able to use 2 6v 1 watt panels to get it to work. Almost every build I see uses 1 panel between 4 and 6v. Am I missing something?</p>
<p>Those car chargers are built for 12V car batteries. Some car chargers may only work closer to 12 Volts, but some may work at lower voltages, but not guaranteed. Maybe the other people got lucky and bought a car charger that works at lower voltage. Be aware that dropping the voltage from 12V to 6V is VERY inefficient and will cut your power output by half!</p>
<p>Thank you for putting that to bed for me. I suspected as much, but its nice to hear someone confirm it. </p>
<p>Yes, that is why I made Solarpad and Open Source project for people to see what's inside and what works.</p>
<p>I have ordered a few USB boost circuits. LOL, there are less than half the price I paid for the charger ($5).... Go figure. You live and you learn.</p>
<p>This is great. With all the things going on around us about solar energy we forget that fundamentally <a href="http://www.sunipod.com" rel="nofollow">solar energy</a> <br> is the natural evolution of the electricity, power and energy industry. <br> If the consumer also becomes the generator and all are electricity self <br> sufficient where <a href="http://www.sunipod.com/solar-power-station-lowers-electric-bill.php" rel="nofollow">solar solutions</a> seem to be going then imagine what fantastic future we can build for ourselves.</p>
<p>I agree, this goes beyond green technology. It's just technology that works, like any other tool we use. But like any technology, high quality means it will last longer and work more effectively.</p>
One an buy a 18560 battery with solder tabs. Soldering directly to a batteries terminals heats the battery internally which is not a good thing.
<p>First, I recommend using the Panasonic NCR18650B batteries because they are the best on the market with verified and tested 3350mAh capacity. These batteries are hard to find with solder tabs.</p><p>Second, the solder tabs that are attached are spot welded on anyways so the battery gets hot during any manufacturing process and it's hard to control the dimension of the tab, which may make it too big to fit in the tube.</p>

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Bio: After being laid off in 2009, I got rid of my car to save money. The difficult transition from a car to a bicycle led ... More »
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