I have a 2020 Sprinter. I do not have an aux battery. I want to put one in the space provided under hood. I also want to connect it to main battery to charge it as I drive (cut off switch when stopped). I also want to hook up an inverter 2000w to aux battery to charge at same time for additional power. What kind of battery 12v 200Ah should I put UNDER HOOD that I can charge when it gets cold? Is that a good idea? It's kind of made for that. I'm worried about the cold Temps overnight. Should I disconnect the aux battery when starting out in the morning and wait until it warms up to start charging? Battery recommendations, and any thoughts or ideas would be greatly appreciated. Thank you.