Using a Power Inverter in a Plug-in Prius

The wise way to have the inverter connected would by with the car in ready mode and letting the engine to start when it needs to replenish what you'r pulling from it.
The alligator clips will work as an extreme temporary fix, I would use a more robust connection directly to the battery terminals with easy interconnect connectors like this or something similar.

 

Terrell Smith has made a very nice video for inverter installation:

He has set his up so that he unplugs and stows it when not in use. When he's using it, he has it all exposed, so cooling isn't an issue.

One caveat: although he refers to the 140 amp rating of the fuse that is right at the battery terminal, it's best to use the inverter when the car is in READY, and the current is not then coming from the aux battery, but rather from the DC/DC converter, with its slightly lower limit.

He chose a Xantrex, true sine wave inverter, which happens to be the same one I'm using, though I picked their 600 VA model instead of the 1 kVA that he chose. The Xantrex has a nice remote-control feature, you can turn it on and off with a button located elsewhere, connected by a modular phone cable.

In my setup, the inverter's down in the spare-tire area and always usable, with an extension cord into the cabin for plugging little things into. However, if I ever wanted to run a big thing for a longer time, like the breadmaker, I would probably lift out the cargo box to have better airflow around the inverter. I put a remote button up on the dash, also wired so the inverter knows when the car is READY or not.

There isn't a video for my setup yet, but there are some photos/description in this post.

-Chap