Rmack1,
Rock Creek is a great place and I trust you had a super time.
Some comments that may, or may not, help:
- I suspect it wasn't all that cold down there this time of year. Maybe it got into the upper 20's for a few hours, but the thermal mass of the batteries would negate most of that. However, as others have said, several factors can add up in colder weather to deplete batteries quicker than you might experience during the summer months.
- You mentioned "one light" on the battery monitor so I have to assume you just have the idiot lights that come with most rigs. For winter camping, I would encourage you to get a better monitor such as
Trimetric or similar, or, as a minimum, use a voltmeter to monitor your battery capacity.
- If you plan to winter camp (which I encourage because it is a great time to be out), you might want change to a different battery charger that has temperature compensation. Even a replacement non-temperature compensated charger is likely to be better than the stock converter....if that is what you presently have.
- I recognize you have checked the battery age, but have you checked to see if the batteries have sufficient water in them? And have they been maintained? Well maintained batteries can last a long time, but poorly maintained batteries will quickly fail. Also, I assume you know this but just in case, the battery terminals need to be clean.
- If I had it to do over again, I would mount AGM batteries inside the rig where it is warmer, rather than wet cells mounted outside. But too late for that now as I don't want to spend the money to change.
- Solar and as many batteries as you can hold and carry is, IMO, the best solution. I can camp for many days at zero degrees (F) with my four batteries (6 volt) and solar system (300 watts).....without a generator.
- Reduce you power consumption as much as possible.
Incandescent lights use a lot of power especially in the winter months when they are on more. Consider switching to LED's.
Also, consider an alternative to the built in furnace at least while you are awake. There are many possible solutions, all of which have their own pro's and con's so investigate this before you jump.
I hope this helped.
Steve
On edit, it looks like NinerBikes beat me to some of my suggestions.