I have a small house measuring ~ 8m x 4.5m. It is in Indonesia and power outages are expected daily. Probably the daily power outage is on average less than half-an-hour, but sometimes the outage can be the whole day (9am till 5pm say).
I have various appliances that run on 12V:
- a wifi router/modem (1.5A)
- a burglar alarm system (1A)
I also want to install a CCTV system. There are two options for this, either a 48V NVR with POE sending out 48V to cameras, or a 12V NVR (I believe 15W, plus the hard drive) and the cameras (around 6W each) being individually supplied with 12V.
Anyway, I want to have these things as 'always-on'.
So I am looking at:
- deep cycle conventional 12V lead acid battery
maybe 220V inverter
Note that I am not backing up the whole house, and I am remodelling the house including replacing all wiring, so whether I have an 'always-on' circuit on 12V or 220V is not particularly an issue.
Anyway what I can see is that if I power 12V directly from 12V than obviously that's more efficient than converting 12V to 220V then back to 12V, but I am not sure how much of an issue this is in practice as the battery obviously needs to be somewhat oversized in any case.
On the other hand presumably I will have transmission losses with such a low voltage, and I will need to fit special 12V sockets and provide a whole-house 220V -> 12V transformer for when the system is running on mains, so the infrastructure costs aren't obviously lower than keeping everything on 220V.
The main advantage seems to be a slightly smaller battery. How much smaller?