I make an assumption...
You are asking about making upgrades and changes to the system.
I take it you have identified your travel plans?
- Weekending at an RV Park?
- Visiting friends and family and "Mooch-docking" using their shore power?
- Overnight without shore power? Walmart/Cracker Barrel - etc.
- Longer term off-grid?
Each of those seemingly "simple choices" carries a specific set of requirements:
Refrigeration, Microwave, Stove, coffee pot, Hot Pot, BBQ, Video, CPAP, Airconditioning, etc.
These components have use cycles that can be calculated with reasonable accuracy to create your
CONSUMPTION (requirements).
Now, next, is when you get concerned about sizing, and modifing, and that is comparing your consumption with the Van's
CAPACITY. Here you'll be making choices about the nature of power supply and chemistry - wet cell, AGM/Gell Cell/Lithium. Depth of Discharge and Battery bank size are the entry points to this step in my opinion. [Naturally BUDGET is a major factor as well! I could say
COST, but that would be after the near final itteration of your journey through this. ]
Finally more electrical confusion to sort out; what and how will you
CHARGE? Will you be using a generator, solar, underhood (Alternator), and the frequency of recharge based on your chosen capacity.
These are pretty straight forward steps along a process, but I find it useful to first understand the travel plans. Perhaps you have then you've made the first step. The 3 C's then need to be itterated, to get to a plan you can implement.
And, as booster has said - there are a lot of helpful members here and YouTube has some good info you can tap into too.
I've attached a zip file of a spreadsheet that might provide some utility in "walking" through the process I've suggested, before breaking out the checkbook.
Cheers - Jim
NOTE: I'd add the "hidden costs" of CONNECTIONS, all the wire, connectors, tools etc, but that is for another discussion. At this point, you'll have a pretty sound estimate on the COSTS. Guess that makes it 5 Cs!