Not a complete beginner but new enough. I installed an all-in-one charge controller/inverter (LV1012, 400Ah lithium battery) that has solar (400W) and utility inputs that work beautifully, but has but no input for the van (Sprinter 3500, 2015) battery. The system software also allows switching between solar and utility. We live in New England so there have been times that we've had to go to a campsite to charge up. Is there a way to hook the van DC into the system. I've read about DC-DC chargers but not sure how that would work. Thanks!