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CERTAINLY that is a valid question. Perhaps now going after an EE degree??
I am NOT a certified mechanic, but I AM familiar with auto electrical wiring and the parts about what the wiring can support is fairly accurate. The wire sizes are only almost adequate for the fuses, and often the assorted voltage drops, both on te feed side and on the "ground" side are not to be ignored. And my two inexpensive inverters, 400W and 800W, each draw a bit over ten amps powering a 100 watt incandescent bulb. So they are not so wonderfully efficient. And there is no way that the inverter input terminals are adequate for what the rated output operation must draw, at least on my inverters.

 

I'd like to use my leaf as a backup emergency power source instead of my generator since it's silent, odourless, cheaper and more convenient. As the leaf doesn't have a 240V outlet like some newer EVs, and since 240V converters that are powered directly from the 400V traction battery via the CHAdeMO port are prohibitively expensive and not easy to buy, the most feasible way to take power from the leaf seems to be via the 12V battery, which is charged from the 400V traction battery by an onboard DC-DC converter that's rumored to have a maximum external load capacity of 1500W (2000W max output minus 500W of the car's own internal 12V loads).

I plan to use a large (100Ah) battery as a buffer between the leaf and the inverter. So the power flow would be something like this:
Leaf's onboard 12V battery -> Jump leads -> 100Ah buffer battery -> 5000W inverter -> house

Is there a way I can configure this circuit to limit the draw on the leaf's DC-DC converter to only 1500W (about 135A)? The only house load that will actually go over this figure is the microwave (1700W at the plug) but that only works for 30 seconds at a time. I'm hoping that the jump leads will have enough resistance such that the buffer battery and leaf battery will supply at least 200W to the inverter while the microwave is running (meaning only 1500W from the DC-DC converter), but I'm open to any suggestions regarding the whole idea. The top priority is to protect the leaf's DC-DC converter from overload or electrical noise since it's expensive and labour-intensive to replace.

On a related note, my spouse has a second Leaf. Is there a way to parallel them safely so each Leaf only delivers about half the load? I'm not sure whether simply connecting the jump leads across the internal 12V batteries would cause unintended large current flows between that could damage the converters.

i have been doing this for years without any problems, my house runs off a 48v inverter (with a working range min 45v max 60v) that is powered off a Nissan leaf battery from a written off leaf reconfigured to 55v, then the house battery is charged using a 12v to 55v 900w DC-DC boot converter from the lead acid battery of the nisan leaf on the drive, while the leafs onboard DC-DC converter is replenishing the 12v battery on the fly as im drawing 900w from it this it does not go flat. i can recharge my house at 1.8kw over night since both mine and my wifes leaf can each feed 900w to the 55v battery in the house during the cause of the night. then when the sun comes out in the morning, all reverses and my solar system recharges the 2 leafs back up along with recharging the house battery and were all good for round 2 when the sun goes back down.

i do not recommend parallel connecting the two 12v leaf battery's though, while this would actually work with regards to distributing the load between the 2 leaf DC-DC converters, it would amuse the 2 leafes have equal capacity and grade battery's yet in practice that will not be true and your best leaf battery will slowly degrade to the quality of the worst of the 2. when parallel connecting any battery, all battery's will become only as good as the worst of them all, so one connected as one larger capacity battery, leave them connected indefinitely (not possible in this case since you would then have 2 drive 2 cars side by side with a wire between them forever)

 

i have been doing this for years without any problems, my house runs off a 48v inverter (with a working range min 45v max 60v) that is powered off a Nissan leaf battery from a written off leaf reconfigured to 55v, then the house battery is charged using a 12v to 55v 900w DC-DC boot converter from the lead acid battery of the nisan leaf on the drive, while the leafs onboard DC-DC converter is replenishing the 12v battery on the fly as im drawing 900w from it this it does not go flat. i can recharge my house at 1.8kw over night since both mine and my wifes leaf can each feed 900w to the 55v battery in the house during the cause of the night. then when the sun comes out in the morning, all reverses and my solar system recharges the 2 leafs back up along with recharging the house battery and were all good for round 2 when the sun goes back down.

i do not recommend parallel connecting the two 12v leaf battery's though, while this would actually work with regards to distributing the load between the 2 leaf DC-DC converters, it would amuse the 2 leafes have equal capacity and grade battery's yet in practice that will not be true and your best leaf battery will slowly degrade to the quality of the worst of the 2. when parallel connecting any battery, all battery's will become only as good as the worst of them all, so one connected as one larger capacity battery, leave them connected indefinitely (not possible in this case since you would then have 2 drive 2 cars side by side with a wire between them forever)

Thanks for posting. I have since found a solution for myself as well - I bought a 12V 280Ah LiFePO4 battery. This battery alone will comfortably run the microwave through my 2500W inverter. During power cuts I run everything on this little battery. Then if the power cut persists, I can power the house with the leaf while charging this battery as well. I haven't yet figured out an efficient way of doing that (I don't think the leaf would be too happy with the LiFePO4 battery in parallel with its internal lead-acid starting battery, so I'd have to use an inverter on the leaf's 12V to power a charger that then charges the LiFePO4 battery), but so far I've never had a power cut long enough to have to tap in to the leaf.