Does the Defiant Daylight Adjusting Indoor Digital Timer also uses a battery?

No battery.
This single-pole or 3-way, programmable or dawn-dusk timer is same as GE 15312 sun smart timer, and requires a neutral wire to power the electronics.
GE renamed all their wall timers, or sold their timer business to Defiant in year 2013-4.
http://waterheatertimer.org/Programmable.html#15132
http://waterheatertimer.org/How-to-wire-GE-15312-timer.html

If you want a timer with same capabilities, that uses a battery, and does not require neutral wire, then choose Intermatic ST01 or Ei600 timer
http://waterheatertimer.org/Programmable.html#st01

Gene

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