battery full but no power?

How old is your battery and if you have had it awhile, how have you been maintaining it?  As offgrid wisely stated above you need a multimeter.  Then you can check the voltage of your battery.  Firstly make certain that your electrolyte levels are full or nearly full, if one of those six cells is empty, your battery is likely toast.  Fill any low cells to full using distilled water.  Next check battery voltage using your multimeter - should read at least 12.2volts at the low end.  If it reads that low you need to put it on a trickle charger (2 amp is great) for at least 24 hours.  Read it again at that point, let it set for a few hours and then read again.   Those two readings should be nearly identical if the battery is good.  Also make sure the connections at the battery are tight using a wrench, getting it finger tight doesn't cut it here.

I just re-read your original post and am thinking out loud, how long did the battery sit being connected to the pod?  There are numerous phantom draws that will deplete the battery down below acceptable levels after 10-14 days.  If you don't plan on using it within a week either disconnect the ground (-) cable or hook up a disconnect switch so you can more easily turn off battery power when not using your r-pod.

Speaking from experience, no it is not possessed, but I experienced similar (lights rhythmically blinking) when I had hand tightened the connections at the battery.  By simply using a wrench, and I only got an additional 1/2 to 3/4 of a turn, that was rectified-problem solved.

Your auto has (and the pod doesn't) a generator so that once you are running, the battery will eventually get 100% charged.  Your pod could do the same IF you plug it into shore power and leave it plugged in allowing the online converter to charge the battery.  Your battery is probably quite low in voltage (again using that multimeter that you are going to purchase) and when you hooked up the solar the battery was slowly charging back up but when you unhooked the solar the battery (being close to low anyway) after a short while would give you the same indicators that it did previously, low or dim lights, ect.

There are many podders who leave their r-pod plugged in 24/7 when not in use and it works for them.  In my case (northern Michigan) I pull both 12v batteries out 1st week in November, check electrolyte and give each a 2 amp trickle charge for 24-36 hours, disconnect from charger, then set both on a concrete floor in our unheated garage.  They 'hibernate' there until the following end of April or first week of May (depends on weather) and the process of charging is done again before being re-installed in our 177.  These 12v Interstate group size 24 batteries are used a lot as we usually boondock, they are now 10 years old and still performing well.  One thing of many things I learned here was not to drain the battery down below 60% S.O.C. or 12.2v (using your multimeter) to keep an eye on things before recharging. 

I have benefited greatly from this forum for many years.  The people on this forum are great.

And next weekend's project will be to look inside the battery as described, which I've never done (in my defense it's encased in a really tight anti-theft security bracket which is a real PITA to get off...so have not wanted to get in there and poke around if I don't have to).

So, any recommendations on trickle charger and/or disconnect switch?