12v ignition source needed for battery isolator

[a2thy]

I'm in the process of installing a battery isolator for a dual battery setup and would like to know if anyone had a good idea as to which 12v source would be best to tap into. The instructions say to tap into a 12v ignition source, but I was wondering if anyone knew of a source that would only supply the needed current while the engine was running. I'd prefer under the hood somewhere, but anywhere will work. It's going to be supplying the current to the isolator via a 16 gauge wire per directions on the isolator, so the 12v source also needs to be capable of carrying a load to necessitate the 16 gauge wire.

 

[a2thy]

Bump.

 

[redxlt]

Radio

 

[a2thy]

Thanks, but the radio comes on when you turn the key. I need something that only supplies electricity while the engine is running.

 

[kimcrwbr1]

I think the only thing that is switched when the engine is running is the fuel pump I`m thinking you can use the fuel pump power to switch a relay for the isolator to keep it separate from the fuel pump the relay uses very little amps to switch the power to the isolator.

 

[a2thy]

Ok cool. So you don't think the relay inside the isolator would draw enough current to harm anything if I wired it directly to the fuel pump power supply? Would I need to replace the fuel pump fuse with one of a higher amperage rating or install an additional fuse?

 

[kimcrwbr1]

Naw the relay uses very little power just use the pump side of the fuel pump relay on one side of the coil and ground for the other side and the battery + thru the switch to the isolator.

http://cgi.ebay.com/2-New-Omron-G3NE-220T-US-DC12-Volt-Solid-State-Relays-/270707429010?pt=LH_DefaultDomain_0&hash=item3f076b8e92

I`m thinking something like this would wire in easy enough

 

[kimcrwbr1]

I was just thinking you would be isolating the isolator he he.

 

[a2thy]

So you're saying that I would need to install another part in order to make this work? This is starting to sound a little too complex and expensive for me. I like your idea, but I think I'll just wire it to the 12v ignition source that the instructions were referring to. Anyone know which ignition source they were referring to? I know it's one of the wires in the steering column area, I just don't know which one.