Through experimentation (and dissapointment) I can attest that the base (not the brick) is what regulates the ability to charge. I created a DIY charging base with reflective tape, spring loaded positive and negative "docking bars" and the brick out of my XV-21 base. My bot finds and backs up to the base w/o any issues. It shows that it's charging, however it will NOT charge when getting current directly from the brick thru the "docking bars". All I can say is DAMN!!! Since we can't buy extra docking stations from Neato and there is a stong possibility of buying an incompatable dock from Ebay
etc., it appears we're stuck moving the base from floor to floor, or section of the house to another. My vac will NOT clean my entire first floor on the 3-charge limit. I talked with CS and the rep told me that there was NO 3-charge limit per cleaning cycle! ----- Seems Neato CS doesn't even know how their product works. I've sent a request for consideration in their next software upgrade to allow the USER to determine the necessary number of charges for their situation. If you are having the same issues.. I suggest you make the same suggestions on their "Contact" page.
Love all the info you're all putting into these threads! You're saving me a lot of time trying to make my vac more suited to my situation.