I have 2 6v golf cart batteries that serve me quite well when dry camping. For a typical weekend trip, they have plenty of capacity to get me thru the weekend without any charging. I have even made it thru a 4 day day trip without going below 50%. That's without any furnace use though.
Now as far as coffee... Typically I always heated water on the stove and made French press coffee when dry camping. I have started to experiment with drip coffee using an inverter though. What I've found is that my coffee maker draws about 72 DC amps and as long as the batteries are above about 60% to start, the inverter won't alarm.
So for me, if it's just a quick weekend trip and I don't plan on running the furnace, I'll make drip coffee. For longer trips or if I expect to run the furnace, back to French press coffee!