A typical mid range EV (say 250 miles) is about 50 KWH. So to just get 20% you only need 10KWh. The smallest generators are around 12KG and put out about 1.1KW

A typical mid range EV (say 250 miles) is about 50 KWH. So to just get 20% you only need 10KWh. The smallest generators are around 12KG and put out about 1.1KW but they tend to only run a couple of hours due to small tanks. About double that at 22KG you have something with more reasonable run time and puts out 2KW (https://www.amazon.co.uk/Panana-Aokaidun-Portable-Inverter-Generator/dp/B0CFLD55RW https://www.amazon.co.uk/Panana-Aokaidun-Portable-Inverter-G...) and within its typical 6 hour runtime is going to get you 20% and in a 24 hour cycle with refills gets you nearly a full EV. This suggests to charge the car fully you would need about 4 x 4 Litres of fuel, that is 16KG of fuel and 22KG of generator your carting around in the back of the car, its basically a persons extra of weight for one refill which would take about day to complete.