Re: HELP Wiring a Stereo to work when the ignition is off
With the second battery installed, run a positive and negative wire from the battery to the where the radio is. You will then split that power wire into two leads, one lead will connect directly to the radios 12v battery wire (always hot) and there should be a fuse somewhere in that line, likely one is included on the radio wire itself. Next you will need a toggle switch, the second lead will run to the toggle switch source terminal. You will also split the ground wire into two leads with one leading to the stereo and one to the toggle switch. Next you run the output wire from the toggle switch to the radio. Drill a hole next to the radio and install the toggle switch. Now when you want to turn your radio on, you can use the toggle switch to simulate turning the key on, but the radio will not lose memory because the always hot wire is connected directly to the battery. You can go one step further and purchase a 12v digital voltage indicator from amazon for about $10 bucks. Tie this into the output wire from the toggle switch that powers the radio and install it in the dash next to the toggle switch, when you turn the toggle on to use the radio, you voltage indicator will display the voltage on the battery so that you can monitor the battery level/tell if the battery is charging...
Note that if your toggle switch will need to be rated to handle whatever load is expected of it, if it is just a small toggle, you can utilize a standard bosche relay in the circuit to feed the radio..
