[Michael] took a battery charger meant to be connected to mains power and converted it to work with a solar panel. This was a traditional 4 cell charger which charges the batteries in pairs. He kept that functionality, but added USB charging with a special over-current feature. That’s because his Android phone has a fast and slow USB charging mode. The slow mode makes sure that it draws 500 mA or less to stay within USB specifications. But the fast mode draws more current when the phone detects that the USB connection is attached to a wall charger. [Michael] added a switch that patches a pull-up resistor to the data line, signaling to the phone that it’s okay to switch to fast charging mode.

As for the power supply itself, you can see that [Michael] snapped off the part of the circuit board that housed the original regulator. He’s added his own 5V switching regulator which offers a wide input voltage range. This is connected to two banana plug sockets which can be connected to the solar panel.

This miniature “spy satellite” may not gain the ire of the Chinese People’s Army, but it will certainly look rad on your desk.  Besides looking cool, this “satellite” is able to transmit video up to 300 feet away and has sun tracking solar panels for battery recharging. Additionally, it has a LED “thruster” and speakers.

One cool thing about this build is that the body was made out of a lamp from Goodwill. Recycled/thrift store enclosures always make a good addition to your project as they won’t break the bank. Additionally, they may yield some other bonus parts when taken apart. In this case, the lamp fit into the project scope perfectly, but anyone trying to duplicate it might not be so lucky.

Creative use of other household materials rounds out this build, with solar panels taken off home garden lights, and part of a nose hair trimmer used as the “thruster” body. This well-build project is a great example of how to convert household items into something totally different and unique.

The polished quality of this hack isn’t quite there, but we love the ingenuity and exploration exhibited. [Paulie1982] shows us how to make an old cellphone work with the rays of the sun.

You can see above that he’s added photovoltaic solar cells to the back case of what looks like an old smart phone. He grabbed the cells from two inexpensive solar landscaping lights and inserted them by cutting holes in the case and using black silicone sealant to glue them in place. Each can pump out about 3V and together they get above the 5V threshold that he needs to do some charging. See the build process in the video after the break.

From what we’ve seen there’s zero consideration of current in this hack and that’s what makes us skeptical. Still, we love the idea of trickle charging and we’d love to see some speculation in the comments about how to improve upon this. Surely the additional hardware necessary for proper regulation, etc. could be fit in a custom case cover like the one used for this inductive charger hack.

[Phillip Torrone], one of the original crew of HackaDay, now working with [LadyAda] tipped us off to this video of her explaining the device they built for configuring the charging circuits to be used with their solar panels. Unlike most of their tutorials, this one is not intended to be a final product sold on their store. Rather, this is a project that helps them deliver the best quality they can.

The unit itself is built around an Arduino and can log the statistics to an SD card, show battery voltage, panel voltage, and current from panel to charger. You can see in the video above how she uses this to refine her design in real time for optimal results.

The 25th Chaos Communication Congress is underway in Berlin. One of the first talks we dropped in on was [script]‘s Solar-powering your Geek Gear. While there are quite a few portable solar products on the market, we haven’t seen much in the way of real world experience until now.

[script] selected a four segment folding solar panel after some research. He pointed out that solar is currently more of a necessity technology than money saving since the panels can be very expensive. For connectors, he recommended ones that were safe, polarized, and difficult to short, like the RIA connect 230 series he used. Most of the device plugs were easily purchasable, but some had to be salvaged from old AC adapters. A key component of his setup was the adjustable voltage regulator. It’s based on the LTC3780 buck-boost controller which is 98% efficient and can be adjusted from 4V to 25V.

[script] covered some of the problems he ran into in use. The first was an Nokia that refused to charge until a resistor was added to reduce the current delivered. Less sensitive devices like portable peltier fridges will work without any issue. For laptop use, he ran into problems with demand spikes killing the power delivery. He added a large cap normally used in car audio systems to make power delivery more consistent. Laptops can consume as little as 15W during normal use, but when they’re charging the battery, the draw can jump to 50W. On his ThinkPad, he was able to turn off charging to prevent this. He monitored the performance of the panel by building a Kill A Watt style device using an ATmega8 to measure current and voltage and log it to EEPROM.

In conclusion, [script] stated that he was happy with his experience, but that it was still impractical to use the portable panel in anything other than direct sunlight.

Our love for solar projects continues on with this method to make your own solar panels. [Mike] built a 60 watt solar panel from individual solar cells he purchased off eBay. Procuring parts off of eBay normally causes others hardship when they try to duplicate the project, however in this case there are so many types of cells people can use to produce their own unique solar panel. Even cells that are extremely damaged my still be used, as in this example. To charge a 12 volt battery the number of cells in series just needs to be 16-18 volts, and the rest in parallel will supply more current. Charging a battery without a charge controller is not recommended, but commercial ones are easily had. Those not interested in jumping all the way in with solar may want to test the waters by building their own panel and putting it to use as a charging station for your portable gadgets.