dry camping

I would bet after 2 years your battery won't hold a good charge.  The voltage test mentioned above is a start, but you also need to load test it.  The plates are likely sulphated and even if you see 12.7 volts after it rests for a few hours there may be few amps available.  Without it plugged in to AC power, turn on all of the pod lights and the fan on high for an hour.  Let it rest again for 3 hours and do another voltage test and report back.

A good battery, just running the water pump as needed will be no problem.. It will also be running the brain of your fridge, the fantastic fan, lights, and the DSI of your water heater. BUT, if you don't need the furnace, or try to run the fridge on 12v, it should be fine. Follow tool man's instructions on testing the battery pre-trip. You want to see 12.6v or better after the resting period.

As far as charging from the tow vehicle if need, use jumper cables. They move 10x the amps your bargman connector does, a 30 minute idle will bring your battery up pretty far, in an emergency.

So our plans for Memorial Day have changed. We are now going to be dry camping for three days.
Here's the scoop...
We haven't ever practiced proper battery care. I've owned the pod for two years and we rarely use the battery. It is charged before we go out, but has never been trickled over the winter.
Here's the question-
If we are only relying on the water pump for the bathroom, can we get by with one battery? Again, the battery has been allowed to discharge over the winter. I do realize I could always connect to the truck and recharge, but I would prefer not to.
Should we get a second battery in relay or just use the one for the trip.
We may also use the lights.

Thanks!!!