Finding an ignition source connection for Dual Battery System

Submitted: Sunday, Aug 05, 2018 at 17:10
ThreadID: 137085 Views:1099 Replies:5 FollowUps:4
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I have a 2017 DMax and have connected a Dual Battery System with a battery under the tray at rear.
I need to find an ignition source to connect a blue wire to because of the alternator.
Has anyone got any ideas on this.
It would be nice to have something at rear eg trailer pin for ease of running the cable. I am 12V illiterate so I am having some difficulty with this.

Thanks in anticipation

Howard T
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Reply By: RMD - Sunday, Aug 05, 2018 at 17:29

Sunday, Aug 05, 2018 at 17:29
Howard T
There will be a wire which become 12v "live at the wiper motor when the Ignition is ON. Can't tell you which colour but it is easliy found by probing the wiper plug with a multimeter set on 20v DC scale or a simple test light. If the wire becomes live when Ignition is on, then that will provide a 12v system signal for your dual battery system, which I presume is a DC DC unit near the battery.

You will of course require a heavy cable to supply the charger unit with a 50 amp capacity. Fuse at battery.
If using the chassis as the negative return, then the negative to chassis connection should be bared to metal and sprayed with a body wax or sealant after bolting it there. That stops corrosion action which can cause loss of connection integrity and heating at that point along with a high resistance becoming a problem.

The rear loom going to the plug for the towbar loom has a Pink wire inside which supplies the system voltage to the relays for L and R flasher wires in the trailer loom. I think it is live all the time for Hazard use/ trailer reasons, but if it is only ON when the engine is running then that would be a place to attach a splice for the DC DC unit Blue signal.
AnswerID: 620535

Follow Up By: Batt's - Monday, Aug 06, 2018 at 10:13

Monday, Aug 06, 2018 at 10:13
That may work with some vehicles but not my old GQ patrol I soldiered a wire to it near the wiper motor then when I put the wipers on you could hear the Redarc bcdc dual battery isolator click on/off with wipers. So probably good to try a temp wire up job so you don't complete the job only to find it failed I changed it to a power supply under the steering column cover.
FollowupID: 893019

Reply By: IvanTheTerrible - Sunday, Aug 05, 2018 at 18:02

Sunday, Aug 05, 2018 at 18:02
Power outlet in the glovebox
AnswerID: 620537

Reply By: Ron N - Sunday, Aug 05, 2018 at 18:48

Sunday, Aug 05, 2018 at 18:48
Howard - "Philby", the bloke with the first post in the forum link below, has the answer for you.

2017 D-Max - picking up an ignition source

Cheers, Ron.
AnswerID: 620540

Follow Up By: IvanTheTerrible - Sunday, Aug 05, 2018 at 21:10

Sunday, Aug 05, 2018 at 21:10
Wow Ron. Exactly what I said! I actually removed the two wires off the socket and ran permanent power from the second battery so I can charge a phone with the vehicle turned off.
FollowupID: 893009

Reply By: Howard T - Monday, Aug 06, 2018 at 09:26

Monday, Aug 06, 2018 at 09:26
I would really like to thank everyone who replied to my help request.
Thank you. It was very helpful.

AnswerID: 620550

Reply By: Grizzle - Tuesday, Aug 07, 2018 at 14:10

Tuesday, Aug 07, 2018 at 14:10
We used this piggy back fuse for our connection for Redarc switching wire. Means you don't have to cut exisitng wires.

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AnswerID: 620576

Follow Up By: IvanTheTerrible - Tuesday, Aug 07, 2018 at 17:51

Tuesday, Aug 07, 2018 at 17:51
Fuse jumpers are great if you have a fuse that is on ignition power that wont glitch the computer. Alas the current Dmax only has them on the inside fuse panel so the power outlet is a more practical location to obtain ignition trigger. Now I will point out the dangers of just picking any ignition fuse. If you use a fuse jumper you would be foolhardy not to use it to switch a relay and relays can glitch or even damage vehicle ECU. A power outlet is designed to be idiot proof so if it is on ignition it is the perfect choice and another plus is for small loads you can power it directly without a relay
FollowupID: 893052

Follow Up By: Graham G4 - Tuesday, Aug 07, 2018 at 21:18

Tuesday, Aug 07, 2018 at 21:18
I don’t disagree with that but we are talking a switching wire here which is basically doing the same thing as switching a relay.

Ford Ranger is just as electronic as Dmax and he has had no issues. I would suggest for this particular use the piggy back fuse is fine.
FollowupID: 893060

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