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Yes, I searched to no avail...anyway, my Bronco came with two batteries but the PO had the second one disconnected. I have the tray and some of the wires with a second solenoid mounted on the drivers side. Does anyone have the schematics for the wiring? Was there a switch in the interior originally? There appears to be some of the wiring going through the firewall. I would like to set it up again as factory if not I guess I will just run them in parallel. Any help would be greatly appreciated..
 

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The accessory relay energizes a solenoid (Looks like a winch solenoid) on the fenderwell that ties the two battery positive cables together. That's it. There's a pigtail for running aux loads off the aux battery without using up the main battery with the key off.
 

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If you can't figure the factory duel battery system out, buy the duel battery system from Painless Wiring and use that set up.
 

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I will post up some pics, but this should be what you have BigMikeC:

Wires: Black (Small): B+ from starter relay to accessory relay and female socket end @ aux. battery solenoid
Black (Large): B+ from starter relay to aux. battery solenoid B+
Black/Green stripe: Swtched B+ from accessory relay to aux. battery solenoid coil.
Brown: From ignition switch to accessory relay
Black/White stripe: From aux.battery solenoid to battery.
 

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This is some info I've dug up while researching the factory dual battery set up in my bronco.

These are the parts of the factory dual battery system,

"Auxiliary battery, continuous duty solenoid, a firewall post with a plastic base, the short harness btwn the solenoid and the stud, then the long wire from the stud to the hot side of the starter solenoid, then the harness from the continuous duty solenoid to inside the cab which plugs into the three-hole accessory plug..."

here is a thread from FTE that explains it,
https://www.ford-trucks.com/forums/1471580-dual-battery-wiering-diagram.html

and another,
https://www.ford-trucks.com/forums/1478734-two-batteries.html
 

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Saweet, we will get the next guy who searches for "factory dual battery" lined out all proper like.
 
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