I have a 2018 Ram Promaster city cargo van with OEM 12v 70AH 120RC Sealed Led acid battery and a 160a alternator.
Sitting on top of the battery I have a 1200 Watt pure sine 110v inverter connected with 2 gauge wires and then have a 12 gauge run to the back of the van. I also have a single 12 gauge line running from the batteries hot to the middle of the van that gives in an always on 5v USB source.
To date, my power needs in the van are minimal. when I need 110v, it's for very short periods of time (15 minutes or less) to run 500-800w appliances & tools and when I do I am usually parked with the engine running.
When I've slept in the van overnight I run a 1a 5v fan from 10pm to 6am. My battery has never been below 10v, but I do plan to install a 10v low voltage disconnect to the 12v hot line to be safe. My inverter already has a 10v low voltage disconnect.
However.. In the future, I would like to install a 200 Watt 18v 6a (max) solar flexible solar panel on my roof. It might be overkill, but the 32w x 42l size fits perfectly and will block a lot of sun and help with mid day interior temps. As I ponder how to benefit from this free power, NOTE: I am NOT looking to install or sleep with batteries in the passenger area. I would like to install a ceiling vent rated at 12v 3a when on high (specially a Max Air 14x14 fan 12v 900CFM fan). While I think I can easily run the fan overnight on low (12v 1a) and have no issues starting the van, I would like to run the fan on high (12v 3a) when the sun is strong during the day. Again, I have no plan to drain my 12v battery like a deep cycle. And finally, as I anticipate having more power than I need during the middle of the day even with a 12v 3a fan running, I would like to freeze the content of small 50w 12v freezer (Alpicool C15) during the day (9am-9pm) and then keep it off and closed overnight. I would anticipate interior ambient temps to range from 90F midday to 80F night. The ultimate goal being to keep the van cooler during midday and keep Milk and Cheese from going bad for a week. In a pinch I can always find some ice if need be.
So my questions...
(1) How can I connect the solar panels 20a charge controller (200W 18v 6a panel)to my battery so as not to impact/interfere my cars charging system and visa-versa? do need a switch or isolator? I am presuming my charge controller will have some protections like a reverse diode for night fall leak back.
(2) If later on I want to upgrade my battery to a new dual purpose 12v 100AH 200RC 830CCA battery will my 160a alternator be okay with having to work harder to recover for longer periods of time? Again, I do not anticipate ever draining my battery like a deep cycle battery. I will tell you I have experience with another automotive 160a alternator and a 90AH/140RC battery (running 2 amps overnight) that would get close to 10v many times and never had any issues.
(3) also wondering about Charge controllers that have an output ports. Are their controllers with output ports that can be regulated to 12v? how are they different from connecting directly to the battery? I might not be understanding schematics, but seems like there are controllers that offer Low Voltage cutoff and hours of operations from those ports.. is that right?