I threw out my ancient alarm power supply, then used a Sherlo 6.4A charger with an 18AH battery which fits inside:
Sherlo 6.4Amp battery charger is a robust and high-powered device designed to efficiently charge a variety of batteries up to 18ah 12v.Equipped with intelligent charging technology, the Sherlo 6.4A...
www.alarmtec.co.za
It has 6x1A 12V outputs which I use for:
- CPE
- Old Alarm (battery removed)
- 5V Converter: Router + SIP Phone
- Router
- Alarm beams + 5V Converter to PI Zero
It's pretty DIY, but one could use car chargers for the 5V supplies to keep the DIY to cutting off adapters and connecting wires.
My guess is that this should run for 6h.. just a guess, but the 2h load shedding shouldn't kill the battery too quickly.