12V source

[Grippy]

So I have been poking around trying to find a 12V source for my continuous duty solenoid that is only active when the engines running. There is tons that have 12V with ignition off, and heaps that have 12V with key turned to 'on' but this would be a problem as it will open the solenoid and allow both batteries to be connected for starting. Other cars people use the oil pressure switch, however on the 02 V8 it's a gauge sort of setup and I'm not sure if I want to tap in to it.
Any suggestions fellow Jeepers?

[fester]

Is this for a dual battery set up or something else grippy??? If so that's why the smarter solenoids like the Redarc SB12 are a better option these days. I'm assuming that is the case because you are worried about both batteries being connected.

Otherwise/Either way I presume you are looking for a trigger signal as the oil pressure option would not be a decent current source.

Thinking out loud here:

Is one of the signal wires from the alternator only active when running. I've never needed to look at this but there is an intermittent signal generated for the charge circuit to the dash light. If it turns it off when running (as I expect) you could run a changeover relay that activates your solenoid when the light circuit shuts off.

When probing for a suitable wire are you testing it through to starting the car. This is a guess too working off my diesel setups which tend to power some unnecessary things down when actually cranking. Doesn't solve the issue totally as they would still be linked when first turned to ignition.

Maybe someone like Jaycar have a kit for a delayed start relay.

The problem I think you will find with a modern car, especially with as much electronics as the Grand is that pretty much everything that is powered only when the engine is running will be taking it's signals to or from the ECU. eg oil pressure, water temp, injectors and many things these days get pulsed signals.

you might be able to reduce signal impact on an ECU related feed by running through a relay to trigger your solenoid but again in having to go down this route a dedicated smart charger/solenoid is a far better and dare I say simplier solution.

Might help to know what you are trying to do and why.

[Grippy]

Thanks Fester, yep this is for a dual battery setup.
I jumped and bought the tried and tested Continuous Duty Solenoid, then started poking around trying to find the 12v source, soo much on the WG has constant power under the bonnet.
I knew when I pressed 'buy it now' that I should have bought a VSR instead. Ah well, this is the way it usually works, haha, but now I will be determined to get the thing to work, just to be difficult, and to say I did it.
I'll keep poking around and see if I can find a suitable source, or maybe chuck a big diode on the charge cable to enable current to only flow one way, then be able to hook it up to any 12V that switches on with ignition.

[bodgie]

The DBE140SF is a very good option for dual battery isolation on older vehicles. Newer cars need to a DC-DC converter as the normal run voltage is to low for old style isolators.

http://www.piranhaoffroad.com.au/pro...gement-systems

[fester]

Go for it if it floats your boat grippy but I'd be sticking with the relay set up to trigger the solenoid (if you can find a source). A diode draws current and therefore affects voltage and I'm assuming the bigger the diode the more it will draw. For your second battery to charge as best as it can you want as little voltage drop as you can engineer. You would also want to stick with a basic battery I'm thinking

[Grippy]

So I have come up with a few solutions, either I can wire the charge cable of the solenoid as usual, the the positive for the solenoid switch to straight 12v then the earth of that switch to something that will only earth when the engine is running, just gotta do some more poking, or buy a simple 12v timer thing from eBay, bout 8 bucks or so, programmable to 20 ins or so

[Hayesio]

What's wrong with just using a voltage sensitive relay (aka VSR aka dual battery isolator) like 98% of all other dual battery systems in the world? $70 bucks on ebay, no triggers, no extra wiring, simple and very reliable.