I know there is one near the console and one in the middle storage compartment but are there any near the cargo area?
No cigarette lighters in the Prius. There are 12V electrical sockets in the front, as you describe. The Gen II Prius does not have a socket in the back. I don't believe the Gen III has one either. Tom
So there is only 2??? How can I expand it? (is there a device? I would like at least 3 additional slots).
Depending on what you're trying to connect, you might tryhttp://www.amazon.com/dp/product/B001FB578I?tag=priuschatcom-20 It has two USB ports per adapter.
Well, I need 12v ports only (not usb) since all my devices use the 12v power cable. Is there a device for that?
^^^ There are also triple output expanders in that shape too. Here is another one, wired instead of plug-in. Beware of the fuse limit. More outlets does not mean more total power available.
Some people wire one into the hatch area. Recall that the 12V battery is located under there, so it is easy to get plenty of power. Make sure you use a fuse. Tom
