Is there no easy way to extract DC power from the traction battery?

The "system" that keeps the traction battery charged likely would be "upset" if anything was connected directly to the battery that caused the charging and discharging characteristics to change more than a tiny bit.

Second, an "inverter" with a 240 VDC input is kind of rare and expensive.

Third, 240 VDC is more dangerous to work with than 240 VAC.

I think it has been discussed here before but never got past the discussion stage.

 

Let me rephrase your question, there is no obvious safe way to connect to the HV battery to power an inverter.

Toyota went to some lengths to completely isolate the HV battery when the car is off, so first responders are not killed.

If I was intent on using the HV battery to power an inverter I would study open source J1772 devices that currently safely allow high voltage DC connections. (Your car would take the role of the EVSE and the inverter would be the vehicle side) That would be as safe as the Prime.

https://en.m.wikipedia.org/wiki/OpenEVSE

 

For an overview of the ways people who are currently doing it are doing it, and answers to several of your questions, you can refer to this knowledge base thread:

Electric power from a hybrid, connecting inverter to the high-voltage system | PriusChat

An added inverter is generally connected 'downstream' of the system main relays, so the expectation that the battery is isolated when the car is off isn't violated.

(An inverter typically will have some capacitors on its input that will continue to put voltage on the orange wiring for a few minutes after the relays open. But then, that's also true of the inverter under the hood.)

Taking your title rather literally, at 200+ volts, it is all too easy to extract DC power from the traction battery! You can quickly demonstrate by making one wrong move while working around it. That's why Toyota worked so hard on the isolation and interlocks.

 

Huh, I thought somebody already did this.

Most of the batteries actually put out between 245 to 355 VDC depending on the model. 2017-2022 Prius Prime is 351.5VDC, although the 1st gen Prius Plug-in's battery puts out 207VDC (these values are all nominal). The highest I've ever recorded on my PiP was 222VDC, although fully charged it was typically 221VDC. Toyota already builds in 2 inverters as well as a DC/DC converter and all are already monitored and controlled through ECMs. I'd try to see if you could access one of them. For instance there is the inverter for the AC and/or heat pump unit (if it has one) and a separate one for each motor (although the newer hybrids use e-Axle and are integrated).

 

'easy' is a loosely defined term