Every want to make a portable Pi and all you have is a 12 volt battery? Or have you made a project using a LCD with a 12 volt battery and another then another 5 volt battery for the Raspberry Pi? This instructable will show you how to turn a cheap car 12 volt USB charger into an adapter that can use 12 volt batteries to power the Raspberry Pi.
Step 1: Step 1: Materials
Step 2: Step 2: Disasemble the USB Charger
Take everything apart and set aside the circuit card.
Step 3: Step 3: Soldering
The positive terminal is the fused center connection. The negative terminals are connected to the USB casing. To avoid confusion, I recommend a red wire for positive and a black wire for negative.
Solder the red or positive wire to the back of the circuit card, where the fuse connects. The black or negative wire may be soldered to one of the USB ground pins.
Step 4: Step 4: DC Connector
If using a DC connector with screw terminal like I did, your almost done. Just place the wire in and screw down the terminals. If you used a DC jack from some scrap, you will more than likely solder the wires on.
Always observe polarity. Normally, the positive voltage rides on the center pin of DC power supplies, but it may be reversed on some. If the polarity is wrong, you will damage the Raspberry Pi. Be careful.
Step 5: Step 5: Test It
Connect the adapter to a power supply and watch the Raspberry Pi run...