wiring stereo to second battery

Hi all, just fitted a dual battery system and now I am going to switch the stereo to the AUX battery, my question is currently the head unit has constant power and then ACC power which switches the radio off when you turn the key off. What is the best way to wire it up so I can still have it turn off when I turn the car off but them im guessing a relay and switch to switch it to constant power from the second battery when the car is off without switching to accessories with the key? does this make sense? cheers

use your original ignition wire to activate a relay and run the constant power from the secondary battery through the relay. this way all power for the radio will be supplied by the secondary battery but you are using the original ignition circuit to create a new ignition circuit off of the new battery. the relay will keep voltage from each battery separate. just wire the radios constant 12v and ground wire straight to the new battery.

soundnsecurity wrote: use your original ignition wire to activate a relay and run the constant power from the secondary battery through the relay. this way all power for the radio will be supplied by the secondary battery but you are using the original ignition circuit to create a new ignition circuit off of the new battery. the relay will keep voltage from each battery separate. just wire the radios constant 12v and ground wire straight to the new battery.

Thanks for the response, any chance you could put the relay numbering beside what wires go to where?

85: to original ignition 86: to ground 87: to new battery + 30: to radio ignition wire (usually red)

Thank you very much for that

Will that then keep the radio on when I switch the ignition off, I want the radio to still go off with ignition but then power it up again via a switch that way I don't have to keep turning the radio off when I turn the ignition off

huh? so you want the radio to turn off when you turn off the ignition but you want a switch to turn it back on when the key is not on? ok, then just add a typical on off switch wired also to terminals 87 and 30 of the relay. but if you do then then you risk running the battery down because it will not turn off without turning off the switch.

Thanks once again, yes that is what I want because I don't want to run the risk of flattening the main battery with anything else that runs with the key on accessories, so normal use I will have the switch as normal and then if I am out and have the stereo on for longer periods I would take the key out and have the stereo on.