I know this is an old thread, but I found it in a Google search for ways to suck lots of DC power out of a Leaf and found it very informative.
I've been thinking of a much more ambitious way. That is, instead of pulling power through the car's DC-DC converter, connect directly to the 400V high voltage battery and use it to run one or more slightly modified PFC corrected switching computer-type power supplies. These will give you multiple voltages, though only 12V is likely to be useful in a radio setup. The big advantages are in being able to pull more power than the Leaf's own DC-DC converter can handle and to save a lot of copper and I^2R losses by running 400V rather than 12V most of the way to several loads, which might have to be 10-20 m away.
I'm VERY well aware of the potential hazards associated with a 400V 24 kWh battery pack that's "always on". I'm an EE with a lot of experince in power circuits and I believe i can do it safely as long as I have enough information about the Leaf's electrical supply system. Naturally I will have cutouts and fuses all over the place. But I do need to know the best place to make the connection to the Leaf's HV supply. I don't want to bypass any battery current shunts that might confuse the car's state-of-charge estimate, i don't want to bypass any safety cutouts that disconnect the pack when a cell in the series string reaches a safe minimum voltage, and I don't want to confuse anything else in the car that might be wondering where all that DC power is going. Basically I want to suck as much 400 V DC as I can out of the pack without damaging the car, confusing its computers or giving Nissan any valid reason to dishonor my battery warranty. And I have to leave enough energy to get home.
My specific application is ham radio''s annual Field Day operation. The theme to Field Day is operation on emergency power, and gasoline generators have long been the workhorses. But I detest generators. They're loud, unreliable, inefficient and dangerous. They invariably run out of gas just as you're having a great run in the contest. And then you have to fuel a hot generator (because nobody wants to wait) in the dark with a toxic, volatile and highly flammable liquid made from dwindling natural resources, the payments for which maintain some of the most medieval cultures in the world.
Batteries and solar panels are often used for a single low power Field Day station, but there's rarely enough capacity to run an entire multi-transmitter operation for the full 24 hours. The 24 kWh in a Leaf battery pack is obviously much more capable.
There's a high power ChaDeMo DC charger almost on my way to the site where I could top off before arriving, and after the contest I could return there to get enough to return home.
Any reason I can't do this?