Tomdnz Posted June 28, 2013 Share Posted June 28, 2013 I am fitting dual batteries into my 1987 Terrano (Pathfinder) The instructions say to find a wire that becomes life after the engine has started, is anyone in the know where to find a wire that meets my needs? thanks in advance Tom Link to comment Share on other sites More sharing options...
Nefarious Posted June 28, 2013 Share Posted June 28, 2013 You need to find a wire that is 0 volts when vehicle is off and 12 volts when vehicle is on. A running condition power source, triggered to the ON condition of the ignition. I haven't torn apart a Pathfinder specifically for this but a multimeter will be your best friend. Are you triggering a relay with the ON condition power source? I'm guessing for some sort of controller for the dual batteries? Are you running cold crank amps for the main and deep cycle for the secondary? Link to comment Share on other sites More sharing options...
Slartibartfast Posted June 28, 2013 Share Posted June 28, 2013 The power to the cigarette lighter comes on with the ignition. Shouldn't be hard to tap into its harness. Link to comment Share on other sites More sharing options...
Nefarious Posted June 28, 2013 Share Posted June 28, 2013 Just make sure an ACC triggered wire is okay. Cig lighter is on accessory. Should still work but make sure they aren't asking for a wire that's 12v with vehicle running but 0 volts with accessory on and vehicle off. Link to comment Share on other sites More sharing options...
Tomdnz Posted June 29, 2013 Author Share Posted June 29, 2013 Just make sure an ACC triggered wire is okay. Cig lighter is on accessory. Should still work but make sure they aren't asking for a wire that's 12v with vehicle running but 0 volts with accessory on and vehicle off. The wire that I need to locate, needs to be live once the engine has started and running NOT before. I have a wiring diagram, I don't know how to attach it to this :-( If push comes to shove I could wire a switch. Link to comment Share on other sites More sharing options...
slide Posted June 29, 2013 Share Posted June 29, 2013 Sounds like you'll need to tap into alternator battery light feed wire. Use it to activate a relay if there's much current draw, or you may mess up your charge rate Link to comment Share on other sites More sharing options...
Nefarious Posted June 30, 2013 Share Posted June 30, 2013 (edited) Yeah Cig lighter is no good. You need to multimeter test wires to find one that's 12v when vehicle is running and 0 volts when car is off with ignition set to accessory. Then once you have found it, do what was mentioned by t-ing into it from a relay. If its just for a low current signal wire then a relay shouldn't be necessary. But if its powering a solenoid or something then definitely relay it. Edited June 30, 2013 by Nefarious Link to comment Share on other sites More sharing options...
SkiMachine Posted July 1, 2013 Share Posted July 1, 2013 The easiest option is to take back whatever solinoid you have now and get an auto sensing one. These work by sensing the voltage at your cranking battery's terminal and closing the solinoid a few seconds after the potential is ~ 14V, which happens once the alternator is running. It's pretty much impossible to accidently drain your cranking battery with these. They usually come with cables to run to your house battery as well and don't cost that much more once you consider the hassle factor of the other options. Trying to find a wire that is only on once the engine is running will be more challenging. Most of the candidates I can think of I've immediately disqualified on the basis that they also run while the engine is cranking, when you least want a dead house battery (read: large load) connecting to the system. Basically your best bet is the charge light on the dash, coupled with a lock-out relay on the start ciruit to ensure that "flicker" doesn't cause solinoid chatter and cranking issues when starting. Do not hook up to an ACC circuit (not that you were going to), since sooner or later someone will turn to key to ACC to listen to the radio, charge something on the cigarette lighter, etc - and your cranking battery will end up dead. Usually miles from nowhere. Link to comment Share on other sites More sharing options...
Nefarious Posted July 1, 2013 Share Posted July 1, 2013 ^ good post. This guy knows what he is saying. Link to comment Share on other sites More sharing options...
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