Is there any technical reason that I'm failing to think of that would make removing hte battery holder from the EmonTH and powering it with a 3v AC-DC adapter? At least one of my EmonTH's will be situated in a position where I could easily power it with mains, so that being the case, if there's no reason not to, why eat batteries?
For the battery powered ones, at what battery voltage do they typically start having issues?
Re: EmonTH Power
The emonTH will work down to 0.7 V input to the converter, so says the Wiki.
The easiest way to power it from the mains would be to supply 5 V via the FTDI connector, or if you add a mini B USB (removing the battery holder), via that.