I am currently running a system where I have 12v mains and 12v battery as power sources.
I am using a toggle switch to manually switch between mains and batter when the power fails.
I have been considering using a relay to automatically switch over. The relay can be powered by mains, thus when that power fails, it will automatically fail over to batter.
The ideal situation is that the switch over is not noticeable and I have put some fairly large caps at the load to absorb spikes as well as hold the load while the switch is switched over.
However if I now put the relay on the 12v mains, it will only switch over once the load caps have depleted, and after that any caps on the 5v regulator will also take a little time to discharge, there will be a noticeable switch over.
One solution is to put a diode on the mains line, but won’t this cause a drop in voltage and about a 5% loss? My load can be up to 3A, so I’ll need quite a hefty diode.
Are there any other solutions, suggestions ?