If you can't charge the car where it is parked, then you need a portable way of transporting charge to your car.
Here is what I went with:
I just connected it to the car through both filaments of a dual filament headlight bulb, but a DC-DC converter would be better.
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2016: 128.75L for 1875.00km => 6.87L/100km (34.3MPG US)
2017: 209.14L for 4244.00km => 4.93L/100km (47.7MPG US)