I read the thread and if that guy is looking to make one for himself, this is what he will need to do:
First and foremost, he will need to decide on a battery. Lead acid "Deep Cycle" (aka Marine Batteries) or GEL batteries are what he wants. They allow for more power to be drained that standard batteries. GEL batteries need a special charge controller (more on that in a bit) so decide on the battery first. 12V is a must, the more amp hours the better. GELs are expensive and can be found in mobility stores as wheelchair or scooter batteries. Lead-Acids are less expensive but are larger and heavier - definitely get a sealed one, it's safer.
Second, he will need to decide on a charge controller and solar panel. The type of charge controller he chooses will depend on the type of battery he gets and the wattage/amps of the solar panel. Personally, the one I'm working on has a 15 watt amorphous solar panel from Harbor Freight, a charge controller rated to work with the panel (it can handle up to 7 amps) and a 12V/19Ah LA battery (I want a stronger battery in the future). He will need to decide how quickly he wants the battery to fully charge vs. how much he can carry. DON'T cheat yourself on the solar panel (like those little trickle-chargers) or you will be hauling a heavy useless paperweight.
The solar panel runs into the charge controller and the charge controller runs to the battery. 2 wires, easy stuff. The charge controller does a few important things - it feeds the battery energy that it can handle and prevents power from flowing back into the solar panel when it's dark. Most charge controllers will also shut down the power coming in from the solar panel when the batteries are full to prevent overcharging.
Next, he needs to decide what devices he wants to charge. Does he want to re-charge his cellphone or microwave nachos? Whatever his needs, he will most likely want the versatility of DC and AC power. To get AC, he will need an inverter. I went with a 750watt inverter. DON'T skimp on an inverter. I wouldn't go any less than 400W.
From each battery terminal, he will need to run a wire (that's 2 total). Anywhere from 8ga to 12ga braided should do well. On the positive line, wire in an on/off switch and an inline fuse (2A should work fine). After that, he can hook up 12 V DC outlets (like in a car/cigarette lighter) and after those the inverter which will supply AC current like in a house (many of the larger inverters also have a USB jack).
If this system is meant to be enclosed, he must be careful that it will not overheat. Computer fans are 12V DC and can be easily added to help cool the interior of the container.
Ideally, splices should be soldered and covered completely with electrical tape. You're literally playing with fire here and you can get hurt.
This may seem like a lot of info to digest, but it's really not that hard.
Instructables.com is a great site that has good information on homebrew power stations.
