12v Accessory port in trunk

Two suggestions:
IF you put a "pig tail" directly to the battery, one that is intended for that,
it will effectively be OFF when nothing is plugged into it.

How about putting the cooler in the back seat instead ?
Isn't there a power plug in the cabin somewhere ??

 

Some car fridges have battery-protecting features; they will turn off if the voltage gets low-ish, to leave you still with enough to start the car. (Food gets warm, though.) Mine lets you select from three different levels of low-ish, depending on how daring you are.

I would like one that, if that happens, tells you when you come back how warm the food got and for how long. You'd think that would be an obvious feature, but it's hard to find. There are some that want a network connection and will ping an app on your smartphone, but that's a lot more bells and whistles than I want.

The one I use came with a cord from a cig lighter plug to the strange connector on the fridge itself, and I just cut the cig lighter end off and wired it to my fuse block added at the battery in back. So that cord is just part of my Gen 3 now, and it reaches to under the hatch or behind the passenger seat, wherever I might want to put the fridge.

Car fridges can use thermoelectric elements, or use a compressor and refrigerant like household ones. The thermoelectric ones are cheaper to buy but will use a bunch more energy, be running and making noise pretty much all the time, and be harder to run for any useful period off a Prius battery.

 

I bought one of those once. Koolatron brand, even. I eventually gave up trying to make it useful. By running all-out, it can get its compartment temperature some-number-of-degrees below ambient, where 'ambient' is the temperature in the car. If it's cool out, or not sunny, sometimes it manages.

 

You can't always HAVE what you WANT.
Good luck.

 

A couple of us are TRYING to tell you that you do not "need" that........
But you aren't listening.

NOTE: Most people find that getting a really GOOD insulated cooler and some ice packs
are a much better solution to your "problem".
But you probably won't listen to that either.

 

The "proper" way would be to tap into the Power Outlet No. 1 line at the Power Distribution Box Assembly at connector K20, pin 31. The problem with that is the fact you'd need to pull most of the lower portion of the left side of the dash off to access it. Basically everything below the steering wheel(it's located behind the buttons for the heated steering wheel, auto headlights, 120V outlet switch, etc.). Then you'd pull all the lower interior trim on the left side of the car to run the new wire up to where the 120V outlet is. Then carefully cut a hole in the left cargo trim panel near the 120V outlet to install the new 12V socket. As easy as that. [/sarcasm]

Your problem is that you don't just need a switched power line, you need a switched power line on a high amperage fuse. Most of the easily accessed switched power lines in the back of the car are for lighting and are only 3A or 5A. The 12V outlet in the dash is on a 15A fuse. The USB power ports are on 7.5A and 10A fuses. It doesn't do you much good to tap into an existing line only to blow the fuse every third time your cooler kicks on(it looks like your cooler draws between 4 to 6 amps).

The next best option might be the power supply to the stereo amp under the driver's seat. That's on a 30A fuse and should be switched(unless it only powers up when the radio is turned on). That would require removing the driver's seat instead of a chunk of the dash.

 

Oh. In that case, could you just use the power to the 120V outlet as your trigger? Would make the choice of relay more complicated, but there's got to be one out there somewhere that would work. Only annoyance is that the 120V outlet and the battery are on opposite sides of the trunk, but you could work around that by running the wire under the foam boxes.