I got cheesed off with a wall clock that was eating an AA cell every month, so replaced it with another cheap ( $3) one. As it is a nice unit, but just has an appetite for batteries ( the Chinese are starting to supply 'continuous' movements in cheap clocks now as almost a standard) so i did a quick modification to it. One slightly used 5mm red LED, the existing 560R series resistor for the LED ( old panel indicator that was in the ewaste pile) and some used network cable for the hookup wires, plus a used 1000uF 16V capacitor ( yes it is a Crapxon, but here the ESR is not going to be an issue, and it is not bulging like the rest in the computer were) and some solder and glue, and it is now powered by a lead acid battery that provides my cordless phone with battery back up.
Phone base station uses 7V, supplied by using 2 old burglar alarm charger boards. The first, with transformer, charging a 12V battery, and the second modified ( a few wire links and resistors changed around) to give me a 7V regulated output at up to 2A, though the base is only using 2W. Fits in a used GRP box, so the clock is now on the front panel, on the wall behind me at work. I had to float the output of the charger, as it turns out the base station floats at -60V WRT mains ground, due to the phone line voltage. The 14V VDR to ground on the charger output was very unhappy with this till I cut it off, though another 5 minutes and it likely would have unsoldered itself.