Use the Prius as a 12-volt generator during a power failure?

I’m thinking of tapping my 2007 Prius’ 12VDC “AUX” battery to (essentially) charge a much larger 24VDC battery bank through a DC/DC converter. To this end I am wondering how much I can safely take off from the car’s AUX battery.

The users manual shows the fuse ratings, from which I can get some idea, and I’ve seen inverters with output ratings up to around 1kw from manufacturers like ConVerdent for use with hybrids such as the Prius. I don’t need more than about 350-500W (continuous) for my project so ~40A@12V would make me happy, but of course I’d like as much power as I can safely get without messing up the car or the battery, and without tearing up the car to get to the traction battery. What is a good number to design towards?

If there’s a better place to discuss this sort of project I’d appreciate a redirect. This topic seemed closest to what I'm trying to do & most likely to have the attention of people who might know the answer. Thanks in advance..

 

I think 70A at 13.8VDC would be the maximum safe peak current draw.

 

Thanks. I'm sure I'll be drawing less than that. Likely a little less than 400 watts the way things look at the moment, and definitely less than 700.