Jasyaad - It's actually a 300W system now, which you will see if you read to the end of the thread. It works quite well, unless I'm camped in full shade, which I was at the North Rim of the Grand Canyon. Then, I needed the generator. A small generator will work, mine's 1000W and it is quiet and uses very little fuel. A gallon of gas will last at least 4 days if I have to run it each day (possibly more).
You could certainly run jumper cables from your tow vehicle to the trailer battery to charge it if you want, but that's a very inefficient way to do it.
One more thing - you need a fairly good battery (at least 1/2 charge) to RAISE the top, but very little battery power is needed to lower the top. You just need enough to open the lowering valve (which can also be opened manually). AND, if your trailer has the optional manual lift add-on, it can be raised manually too!
You can reduce the electrical load on your trailer's battery by replacing all interior lighting with LEDs (which I've done). Now, if I turn ALL of them on, it uses about the same amount of current as only one of the EOM incandescent lights. There is still a small battery draw, of course if you use the ventilation fan, the water pump, and there is a small electrical draw from the refrigerator even if running on propane (powers a fan and the electronics).
I would not discount a HiLo based on electrical needs, but I DO admit it is a bit more complicated than a canned ham. However, we ALWAYS boondock unless it's just an overnighter on the way and I've never regretted having the HiLo behind me.
Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH
2014 F150 Platinum 4x4 3.5L EcoBoost SCrew