I see from the specs that the AC200 will need 2 panels in series, right? If so this can make installation harder. I am planning on powering from a camper roof and have read that panels in series can be troublesome since one may be in the shade or not faced correctly and when one panel is not producing the combination does not work (which would be even more true for the AC200 needing 35v). Any thoughts/experience on this kind of setup?
Also, is the battery replaceable with some standard model and can an aux battery be used?
You don’t neccessarily need the panel(s) in series, but the panel (s) need to output a minimum of 35 volts. A single large panel will work if it meets the minimum volage of 35 vdc under load. Any panel you use will need to be completely unshaded to produce usable watts and and every effort should be made for that to happen. I would suggest a combination of hard mounted rigid panels and a couple of soft, foldable portable panels (like the Bluetti SP120 or similar) that can be positioned when the situation permits to allow panel aiming and eliminate shading. This way you still get the benefit of hard mounted panels but have the option of using portable when you are parked and cannot get good sun. All the panels could be combined in perfect sun to get max watts. Another option would be four smaller panels in two pairs of series connected panels. These two pairs could then be connected in parallel and you would get your series voltage requirement as well as having the parallel advantage you mention above.
The battery is not user replaceable and long before you run out of the battery life cycles, I promise that far down the road something more capable and less expensive will be there to replace the AC200 when your batteries no longer produce effectively.
I know of no commerically available aux battery, but there are several youtube videos where people have assembled their own as well as using 48 volt e-bike bateries with success. You can slow charge the AC200 at 108 watts using the car charge method and use your vehicle battery as an “aux” of a sort.