Hook your positive to the positive terminal that runs to the trailer.  The negative that goes to ground on the other battery is the other connection point.  You may want to consider setting up permanent plugs so you can run your solar panel without the need to take the lids of the battery boxes.

Your output connections match your input. 

Love to know what your doing for Solar..

If you have two 12V batteries, then they are connected in parallel, so solar + to either + and solar - to either -.

As said above, just connect to the same terminals that go to your trailer.

That should work very well for you! Anything smaller (unless your in a wide open area) is tough to get back what you use.

I have a 130w (full size, not foldable) and it does very well!

Also dual 6's for plenty of power.

I tend to mention this a bit, it's important if you have not yet. Do an energy audit. See how many amps/watts you actually use. You can estimate it on paper, but a good cumulative meter is better. 

Do you have a link you can share for the "130w" that you like so much?

Do note that if you go with 6V batteries, the capacity in Ah does not add. Two 100Ah 6V batteries only give you 100Ah at 12V.

If you're not running an inverter, or something that draws a massive amount of current, there's really no advantage to multiple 6V batteries in series. 

True if your a weekend warrior, yet go for any distance (week or so), boon-docking, and you'll want the dual 6's.
 

Sorry about being late on this..

Mine are dis-continued, but I'm a big fan of this site. Panels (both hard and flex) can be purchased for $1 a watt.

http://www.aliexpress.com/wholesale?catId=0&initiative_id=AS_20180820040044&isPremium=y&SearchText=100w+solar+panel - http://www.aliexpress.com/wholesale? http://www.aliexpress.com/wholesale?catId=0&initiative_id=AS_20180820040044&isPremium=y&SearchText=100w+solar+panel - catId=0&initiative_id=AS_20180820040044&isPremium=y&SearchText=100w+solar+panel

I still debate going flexible.

With the normal losses due to module heating (10-15%) and battery roundtrip efficiency (15-20%), not to mention manufacturer rating optimism and conductor losses, I use an assumption of about 30AH per day per 100 watts here in the Mid Atlantic under typical summer conditions. But I'm lazy and mount my modules horizontally and don't move them.  Again, I'm a long term solar guy but just want to be realistic  so as not to set too high of expectations.  YMMV. 

Solar cells are fabricated on crystalline silicon wafers. That is a brittle material. The cute marketing video on the Sunpower website where the guy is folding the wafer works (once) because the cell is very thin. But ask him what happens when you apply constant bending stress to those cells or flex those cells multiple times. Microcracks will ultimately propagate across the cell and it will fracture, often opening the entire cell circuit, which is in series.  Dead module. 

The polymer superstrate used on the "flexible"  modules is not nearly as robust and the glass superstrate used on conventional modules. It will degrade, discolor, and is prone to cupping. Then there is the risk of hail damage. Dead or low performing module. 

The "flexible' modules are intended to be attached directly to a roof or other rigid surface. By not providing back side cooling these modules will run hot, reducing performance and further reducing product life. Much better to use conventional modules in a stand off mounting configuration that allows some airflow to cool the backside.   

Cells in modules are in series, and the current generated by them is proportional to the irradiance they receive, so if the intent is to attach the "flexible" modules to a curved surface like the front part of an rPod, there will be a significant performance degradation because the cells won't all be receiving the same irradiance levels. 

Bottom line, typical manufacturer's warranties on conventional modules are 25-30 years. Flexible ones are 1-5 years. So, if you won't be frustrated if you have to replace your modules every few years at best, and weight is critically important, then "flexible" is the way to go, but be sure you have a way in mind to remove them from whatever they're attached to without causing damage so you can replace them. If not then stick with conventional glass superstrate modules, you'll be a lot happier in the long run. You pay your money and take your chances. 

Very good response! All points well stated!

The absolute best I have seen on my 130w is 6a an hour (battery was low enough that a full charge was happening). Typically, mid 4's (I will see only 2a, in full sun, if the batteries are fairly full which is normal). Which is fine by me, for I only consume 17a-20a daily as I am currently setup.

Again, Well stated!

Your 6A max current is just about right from a 130W module. You might see as high is 7A under perfect conditions. The 2A output is your charge controller doing its thing floating the battery and providing enough current to maintain whatever load you might have operating during the day. You of course wouldn't want the current to be higher than that after full state of charge is reached. 

For a 17-20 amphour/day load the 130W is a good choice as it will also maintain your battery under fall/winter conditions when an average day is about half the irradiance you get in the summer (about 2.5-3 sunhours vs. 5-6). I think you also have a 230AH battery bank which means you have about 6 days (no sun) autonomy to the recommended 50% max depth of discharge for lead acid batteries. That's going to take you through pretty much any extended cloudy period.  I'd assume you essentially never need to run a genny or a grid connection with that setup. 

For myself, I'm running through about 70-75AH/day in the summertime (2/3 of which is running fans, its hot in NC in the summer) so will need to go for at least one 350 watt-ish commercial/residential size module. I've got basically the same battery setup you do. I expect to need to continue to run my genny occasionally in summer and daily in fall/winter. And now the DW wants to be able to run the air conditioner part of the time... 

Which leads me back to your recommendation to the OP that an energy audit be done prior to making a decision on what size solar configuration to get. I 100% agree. Everyone's usage is going to be  different. 

I'm reposting the measured current draw of each item in my 2015 179 here in case it helps folks with the load estimates. If you estimate the daily run time for each item in hours or fractions of an hour, multiply by the current draws and sum, that should yield a pretty good estimate of the total daily load in amp hours.   Pump, heater, and water heater on time is not the time that you have the switches turned on, its the time each of those appliances is actually running.