So I want to power my PSU from a 12V battery, but when mains powered 12V becomes available, the circuit should use that as the power input.

I am looking at all kinds on 1 Channel delayed latching relay boards, but nothing seems to fit my needs.

What would be the simplest setup for latching relay like this? Would rather buy a board that has some circuitry plus the relay.

Well how about using a DPDT relay using mains to power the relay coil?
When the relay/coil is de energized the 12V battery power feeds your PSU and when mains returns relay coil gets immediately energized and switches over contacts to having mains powered 12V feeding the PSU instead.

That would be the most simple setup I can come to think of anyway.

Quote from Lynx on December 22nd, 2019, 03:12 AM

Well how about using a DPDT relay using mains to power the relay coil?
When the relay/coil is de energized the 12V battery power feeds your PSU and when mains returns relay coil gets immediately energized and switches over contacts to having mains powered 12V feeding the PSU instead.

That would be the most simple setup I can come to think of anyway.

Hmm would this mean that my battery negative is sharing the negative rail with the mains supplied 12v, that mains 12v also energizes the DPDT coil and flip the positive off my battery and positive relay connectors on to pass current to my PSU? There are all kindsa spikes when you make/break coils, so could this cause spikes into my battery negative? I think Tesla used battery negative alone for ground plane in some circuits. I have never used a relay before and really have no idea :(

For simplicity lets forget the mains power here and change the premise so that that I have a 24V battery and 24V solar panel. What would be the hookup be with a DPDT? I would think it also would require a cap in parallel before the PSU, if the relay is too "slow"