I have been looking at options to add an aux battery to my 4xe to power a fridge and accessory items in the back. While we could use the main battery and tap into it, I didnt want to take form it nor did I want to chance messing up the electrical. I had a Bluetti 50ah which I either plugged into my solar or the 110 outlet to charge while driving but it was just not lasting long enough. I am about to start the install on this DC-DC Charger solution. Curious what others have done. I put together this diagram to show the intent.