Well, you did come off as snarky. Not sure why you think you need to tell me I need to find some good electrical help when you have no idea what I know. I have wired two separate sailboats up to ABYC standards previously. I simply asked about one piece of equipment that I was unfamiliar with, here, where people would have the answer. I got some helpful advice and then I got you....my lucky day.Wow! At the risk of being snarky, if you don't know, then you need to find some good electrical help or start doing some reading. (A small start: https://cookfb.files.wordpress.com/2016/09/battery-charge-slides.pdf)
-- The wiring on most 7 pin plugs is too small to carry many amps. This will result in a slow charge and, if you don't drive long enough (and you won't) an incomplete charge - kiss of death for lead acid.
-- A battery to battery charger still needs a large cable, probably larger than what you 7 pin has,
-- A battery to battery charger can compensate for small voltage drops. More to the point, its charging profile is probably a better match for your battery than the profile of your vehicle's charging system. (Especially if you have a newer vehicle.)
-- Most battery to battery chargers incorporate proper isolation to keep a dead camper battery from draining your vehicle battery.
All of the above grossly over simplified, but, I believe correct.
Hope this is helpful.
It was never my intention to give offense. Please take another look at your question. You offered no information or background, and thus you are quite correct - I had no way of knowing what you know. Your question is not what I would expect from someone who has wired two boats.Well, you did come off as snarky. Not sure why you think you need to tell me I need to find some good electrical help when you have no idea what I know. I have wired two separate sailboats up to ABYC standards previously. I simply asked about one piece of equipment that I was unfamiliar with, here, where people would have the answer. I got some helpful advice and then I got you....my lucky day.
Some of us would argue for a larger wire, depending on the battery bank, etc. I used a pair of 0 AWG cables, but, doing it over, would have used a single 0 AWG. But that was a 600+ Ah battery, about 25 feet from the alternator.I would just plan on running 6AWG wire with inline circuit breaker to the back of your vehicle with Anderson plug at rear bumper. On the trailer side DC-DC charger with Anderson plug to front of trailer. Use your 7 pine connector to handle trailer lights / brakes and the Anderson plug for charging duties.
An issue with computerized vehicles is that if the vehicle does not detect the trailer it may turn off the charging.News you can use?
-- A major drawback with some (most) factory wired 7 pin connectors is that the gauge of the wire is probably too small (i.e. gauge too small) to pass enough amps to charge a camper battery during the time that the vehicle is running. This is especially a problem with lead acid where getting a full charge is essential to long battery life.
-- A second issue is that the charging profile of your vehicle may not be appropriate for your camper battery. The new "smart" alternators increase the chances of this. A DC-DC charger can fix this problem.
-- Sadly, because of the question of wire gauge, simply mounting a DC-DC charger on your tailer and plugging it into the 7 pin connector may not work because of the wire gauge and length. But, a small enough battery and a short enough run and you may be fine. You need to check the documentation of your DC-DC charger. (I use REDARC and they generally want a minimum of 6 AWG.)
Again, hope this is helpful.