I'm not totally certain that I understand what a Witty Pi 3 Rev2 does so this is by way of a sanity check that I have got it right.
The documentation says "Thanks to the on-board DC/DC converter (MP4462), the Witty Pi 3 Rev 2 can accept input voltages up to 28V" but when I read the user manual I don't see the power output from the Witty to the Pi. This review on Youtube is the best I could find and seems to confirm my understanding.
My project, which will probably never pass the vapour-ware stage, is to power a pi on a battery from a child's ride-on jeep and install a web-cam nature-watch on my allotment (a remote site for a vegetable garden with water but no electricity). If I understand correctly then I could even turn the pi off during day-time and so conserve battery power. I want to find what* razes my sweetcorn patch each year and and an optional extra would be to deter the varmints.
Bonus points would be for a device that resembles a fox and wriggles its back-quarters as if it is about to pounce. Even better if it could throw lighted fireworks at them.
* Likely contenders are grey-squirrels, rats, and badgers