We have several Roombas in the house and we use a lot (12) of those little "invisible walls" to control where they can and can't go. They're all programmed to daily schedules, but even so, the invisible walls eat up a pair of C-cells every 60 days or so. 24 C-cells every couple of months gets expensive fast. I mean, it isn't going to leave me homeless, but it's pretty annoying to have a device sitting directly under a power outlet, chewing through $20 in batteries each year (and as luck would have it, every one of them is within a foot or so of an outlet). Awhile back we opened all of them up and converted them to run off 3V wall-warts. I had planned to just leave them turned on all the time -- a constant IR beam isn't going to bother anybody. Unfortunately, I didn't realize the invisible walls automatically turn themselves off after about 90 minutes if they're manually activated (instead of being programmed). Worse yet, it isn't feasible to simply program all of them using main power, since the programs would be frequently lost anyway: JEA, our electric provider, is extremely flaky. It isn't unusual to get a brief flicker once a day. I've been wondering -- would it be safe and feasible to wire the battery tray in parallel with the wall-wart jack? (Obviously the two batteries would be wired together in series, and that would then be wired in parallel with the AC adapter to the circuit board.) Would the wall-wart feed the circuit and more or less indefinitely extend the battery life, which would only see a large drain when the main power went off? Or would the lower amperage of the two-battery "cell" be the limiting factor, and the AC adapater would simply act as a second cell and match that amperage, and all I'd do is double the battery life? (Which is still nice, but not really the goal.) When the power fails, is it reasonable to expect that the batteries could pick up the load of supply the memory with power after losing the wall-wart "cell"? Thanks!