This is a take on my previous Solar USB Charger. It's basically the same wiring and design, but with a Lego case because Lego makes everything that much cooler.

Step 1: Parts

Things you'll need (purchase links are in previous Instructable):

Some Legos! I parted this out... obviously you can use a variety of available legos. The base is a 8x16 plate, it was the smallest I could go and still fit the battery. I created 3 "ports" by making space with 1x2 tile pieces and a 1x6 arch piece.
micro USB charging module
Standard USB size battery converter step up module --- this is key as these can varyin their output! you need one that will output enough watts for the fancy smartphones
Battery - you need enough juice to boost the USB - I have here a rechargeable LiPo 3.7V 2000mah, it gets it done.
2 pin Rocker switch
Solar Panel... you could put small ones together or have 1 large one
rectifying diode, this allows your electrons to flow into your battery but they can't glow back outwires to connect your parts
hot glue to insulate wiring and hold parts in place and box together

(If you want to get all your parts from one source (and pay less), you can check out Kitables, they sell 2 versions of this kit (solar and non solar).

Step 2: Wiring Diagram

This is pretty straightforward. I added the consideration of 2 panels instead of 1... you want to wire 2 panels in this manner to increase (add) the voltages while keeping amps the same.

Step 3: Build Your Box

Follow the pics or create your modified version... just make room for the ports. Also, your top plate will need 2 holes for the solar panel wires to travel into the box.

Step 4: Add Switch to Box

Before you solder wires, add your switch to the box. You want to glue it in place, but be careful not to glue the rocker in place (i've done this).

Step 5: Solar Panel

Start by soldering wires to the positive and negative terminals of your solar panel.
Then run these wires through the small holes in your top lego plate. [Imagine these are pictures of the inside of the Lego box top and not my other solar box].
Glue the panel in place on the top of the box panel

Step 6: Diode

Solder rectifying diode to the red panel wire (+) with the black line furthest away from panel.

Step 7: Solder Panel Wires

Solder the diode (from the solar panel/red wire) to the IN+ hole on the charger module.
Solder the black panel wire to the IN- on the charger module.

Step 8: Solder Some Wires

Solder a couple of black wires together and a couple of red wires (color doesn't matter, I just like to use the same ones to keep things clear).
Solder black wire set to the BAT- terminal on the charging module and the red wire set to the BAT+ terminal
Solder one of the black wires (from the set on the BAT-) to the black wire (negative) on your LiPo battery.
Solder one of the red wires (from the set on the BAT+) to the red wire (positive) on your LiPo battery

Step 9: Solder to USB Booster

Solder one wire from the switch to the USB Booster (IN-)
Solder a red wire from the charging module to the USB Booster (IN+)
Solder remaining black wire form charging module (BAT-) to the other switch pin.

Step 10: Layout of Parts

In case you're struggling with how this fits into the Lego box, I took some quick pics of each port and their part.

The USB should fit in one port with the smooth tile. If you obtain a different size board -- there are some larger square boards out there -- just shift your tile placement around to accommodate the board. The USB should still squeeze into the 1x2 tile. After you solder parts on, glue the board down -- go heavy, you'll be pushing on this port a lot so the glue may loosen over time.
The switch should be placed before you solder to it... it will look like the pic. Place glue around the edges.
The charging module fit best under a 1x6 arch. I tried different tile configurations but ended up with too much space on the sides. Let me know if you find a more snug way to build this port. Be sure to slide it under the arch so your micro USB can reach the port. Once you've soldered parts on to this board. Glue it down well. flu

Step 11: Click the Top On

You can glue this but it's Lego so I say keep it available for opening/fixing.

Step 12: Charging

Plug a mini USB cable into the charging module port (the small one).
Takes ~2hours to fully charge Lipo from empty. Or set panel in sunlight, takes ~ 14hours to fully charge.
To charge your device, plug your charging into the standard USB port, turn on switch to direct charge from battery to device.