I have a commercial B45 Keurig I picked up for free, and 4 GC2s w/ a Xantrex Prowatt 2Kw Inverter. Wiring is very short and 000. I also have a Victron Ammeter. I also just ran this a week ago to see the draw on the batteries. The b45 is a little slower to warm up then the other consumer grade versions, but this model draws 115amps for about five minutes, and then every minute or so will draw 115amps for about 3-5 seconds.
I wouldn't leave it running while you aren't actively making coffee due to the fact that it's power hungry just keeping the water ready. However, with my setup it will work fine for us, but I am not sure it's worth it. You can get a Presto MyJo (there are other brands too) which is like a coffee press but will take Kcups. I have one and may just use it instead of wasting my time/effort recharging batteries more often.
