I have a 12v 4A camera system and I want it to switch from AC adapter to 12v Battery in a power failure.
I am planning to use a relay held on by AC power to switch the load to battery when AC goes away.
I want to use a capacitor to keep power flowing while relay flops over.
How do I figure out the Capacitor size?
I thought I would try keep enough capacity for 1/2 second of 12v power at 4A. (relay should switch much faster than 1/2 second).
Thanks for any pointers on this.