switch between battery and power supply to run car stereo

[credfern8807]

So i am making a cooler stereo with a car reciever that i want to run off a computer power supply and a battery when an outlet is not available. I would like to put a switch between the battery and power supply to select which power source i would like to use depending on the situation. My question is 1) can i do this and 2) exactly what kind of switch do i need. Thanks

 

[chuckey]

1. Yes
2. A Switch that can handle the power your receiver uses, I would go for a 12V 20A single pole switch.
If you use a relay you can connect its coil to the power supply and wire the contacts so when the power supply is on, its feeding the receiver and when its off, the battery takes over automatically. A 12 V single pole changeover relay with 20A contacts.
Frank

 

[credfern8807]

so i all i need is a spst on/off switch and a spdt relay rated higher than the car stereo receiver? (the fuse is 10A so above this?) Also, I'm connecting a 80mm fan to the system (12V dc 0.18A) and would like to do the same for this. Can i just wire the fan to the far side of the switch and have it turn on with the rest of the system or do I need another switch/relay for this also?