I am NOT knowledgeable about cars so please bare with me and help a girl out. I have an e-tron '21. I am looking for a portable charger in case I run out of juice on the road or even if the home charger stops working as this is my only car and unable to afford a back-up. I am looking for suggestions on a portable "jumper", please. Also, if anyone can then educate me where to "jump" this car. TIA.