The 14.4 volts I’m sure is from the vehicle running. What happens when you try the exact same setup with the engine off and at a lower voltage?
14.4 volts is right at the upper limit of the car charge spec. In any case the most you would see is around 100 watts of charging which is not much. A couple of things I would suggest. Use smaller 16 ga. wire for your cable from the van to the AC200 cable. You could also use a longer cable to slightly drop the voltage enough to charge.
If it was me, and I went to all the trouble to wire up an XT90 connector with good size 10 ga wire, I would get a 12V to 24 volt step up converter and car charge at 24 volts which would give you a decent a little over 200 watt charge rate. I would suggest a 15 to 20 amp converter for durability.
I believe car mode would also accept around 24v, as some cars run 24v system. If you step up to 36 or 48v, then you should set the system to PV mode. The MPPT will work at those voltages.
12 to 48v step up will allow you to charge even faster (use PV mode). But you need a thick wire as you will be drawing lots of current on the 12v side, like 6 awg (maybe 8). Also it may overly tax stress your alternator if it is pulling too much current.
With a 12g wire, your max amp would be 20-25A range, so stick with 12-24v
Check out this long thread which shows 12 to 48 volt fast charging. It works, but you need to have large ga. wiring and a fan cooled converter to work well. You always need to go larger than your expected capacity on the step up converter so it will run cooler. A 12- to 24 volt step up converter is less costly, does not need the fan and is a wider fit for a lot of vehicles. If you have an additional 100 amps of alternator capacity (to give you cushion and not run your alternator at max rate) and are comfortable with fabbing up what you need, the 48 volt will work fine.