There is loss going from 12v DC to 120v AC, then back to 12v DC. The main reason to use AC
is to power a PC for
Blue Iris or a monitor.
Running directly from 12V DC is common in communications sites. I have engineered
and built several sites over the years. If all equipment runs from DC, it is more reliable
and cheaper to run straight from batteries in large setups. Small sites it is common to
run off of AC and use a UPS.
If you do this, you must add a fuse panel and fuse the power gong to everything, including
the cameras and DVR.
High amperage will melt cables going to cameras, and will start fires!!!
It is fairly easy to build a setup to feed with 12v straight from a battery using diodes.
Automatic 12V/24V 25A Battery Backup Charger Module. Connect to AC-DC power supply to provide instant battery backup power to DC equipment in an outage.
www.samlexamerica.com
This is usable for up to 20 amps of power
You can also buy a power supply with it built in.
23A 120VAC Switching Power Supply with Battery Backup. Uninterrupted DC power from an external backup battery to your critical load during power outages.
www.samlexamerica.com
If you are electronically educated, you could build your own with a power supply, couple of schottky diodes, fuses,
and a way to charge the battery. I could draw a schematic of how to wire. You are on your own past that.