Can you charge a car battery with a portable power generator?
Say you have a lithium, not petrol, generator, something like this or this, which you can charge in the electrical socket at home. If you then connect the vehicle battery to a battery charger (like an Optimate, Ctek, Noco, etc) and plug the charger into the generator, would that work? Is there any reason why it wouldn't be recommended?
Of course if you have your own garage or driveway there's no need - but not everyone does.
Can these things be left unattended? E.g. if you have a garage without a plug. Or would it be a safety hazard? Modern chargers are meant to be left on and unattended for prolonged periods of time, but I have no idea about portable generators.
Would it be dangerous to leave the generator in the car, e.g. on a seat, leave the windows slightly open but lock the car? Lithium generators don't create fumes.
PS Some portable power generators have a 12V output but I imagine that charging a vehicle battery with a dedicated charger is better than directly from the 12V output
PPS What kind of specs would one need to check? Maximum amperage? Is there any particular risk from leaving these "big batteries" in the car while charging the car battery? Maybe if the car is under the sun and the inside gets too hot that could be a hazard?