I want to try boondocking but I don't have solar or a generator. If i leave my camper teathered to my tow vehicle (while running) will it charge the battery and if so, how long will it take?
Depending on if you have the 7 way and your converter can recharge. However it would take a very long time to charge that way. It may be quicker to use jumper cables to charge the battery instead.
+1 what jmkay1 said. Couple of hours, and it's not the greatest charge method. I've done it in a pinch and it sure is cheaper than a generator.
Boondocking is a great experience, but it does take some extra considerations - especially the use of the battery. Always start with a fully charged battery. If you haven't done so already, change all of your PUP lights to LED. (You don't have to change the trailer lights.) Your LP and CO alarms are operating all the time which will draw down the battery. They both have a life expectancy and newer models use less power so make sure they are all up-to-date. Your furnace and water pump draw the most power so use them sparingly. Set the thermostat to the lowest setting you're comfortable with and turn the water pump switch to "off" when not in use to keep it from cycling. You should carry a multimeter with you or install a voltmeter in the PUP to monitor the battery's charge. We use the car to charge things like phones and tablets while we are out driving around. We can boondock for 4 or 5 days without having to charge the battery but we carry jumper cables in case we need a boost. While it is always best to fully recharge the battery, you don't need to wait for the battery to drain down before you charge it. You can connect the jumper cables to the battery and add power at any time for shorter periods of time.
If you don't run the furnace, a single Group 24 or Group 27 battery will get you a week or so of conservative use. It will run the water heater's solenoid, a couple lights for a few hours in the evening, the water pump... that sort of thing. If you intend to use the furnace the equation changes considerably. Dual Group 24's get me around four nights when the temps dip into the 40's, if I don't let myself get below 50% charge. If you are going to be using a furnace without hookups, invest in dual batteries, and possibly in a 100W solar panel. I calculate that with 100w solar and my two batteries, I should be able to approach 2 weeks of camping (which I never would have time for anyway). With 200w solar I could go on indefinitely. If you need to keep a laptop charged and run the furnace, you'll either need a lot of solar, or a 1000w Honda or Yamaha generator to run for a few hours each day. And if you wish to run an air conditioner, you'll need two 2000W generators in parallel.
>> If i leave my camper teathered to my tow vehicle (while running) will it charge the battery and if so, how long will it take? Quite possibly forever if you have a modern tow vehicle. Today, most alternators are controlled by the engine computer and most will cut out (quit charging) below ~ 2000 rpm. Normal idle speeds are on the order of 850 rpm or so -- thus, no charging at idle in most conditions. (The computer MAY kick the alt. back in if it sees a very high electrical load like A/C and headlights on at idle but I wouldn't count on being able to fool it with an extra battery.) JT