Dual batteries
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New User
Joined: Jul 2012
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mainly cranking. with the occaisional camper. Also i run a lot of fog lights and spotlights (not sure if they run directly threw the battery or not?) and the seem to get dim when i slow down. but either way i would like to put dual batteries if possible.
Hotshot
Joined: Apr 2009
Posts: 14,333
Likes: 247
From: Stanley, VA
The reason I asked was because the two systems would be wired differently.
In the factory setup when the truck is not running, the auxilliary battery is isolated from the trucks electrical system.
There is a solenoid mounted near the aux battery, when the ignition is off, the solenoid is open and the battery is isolated from the electrical system, that way if you have a camper or something else hooked up to that battery you can power it untill the battery runs down without having to worry about killing the main battery and not being able to start the truck.
When you start the truck, the auxilliary solenoid closes and now the dead aux. battery will be charged by the alternator.
If you want the battery for increased cranking capacity all you need to do is add the second battery and battery tray, then wire the two batteries in parallel (+/+,-/- like hooking up jumper cables). If you use two identical batteries this effectively doubles your cranking capacity.
If you want it for increased cranking capacity AND be able to power something without worrying about killing the main battery, you'll need to add the auxilliary solenoid and wire it so its closed in BOTH start and run positions but open in the off position.
Here is the illustration from the parts catalog.
Click on the .pdf link to view.
In the factory setup when the truck is not running, the auxilliary battery is isolated from the trucks electrical system.
There is a solenoid mounted near the aux battery, when the ignition is off, the solenoid is open and the battery is isolated from the electrical system, that way if you have a camper or something else hooked up to that battery you can power it untill the battery runs down without having to worry about killing the main battery and not being able to start the truck.
When you start the truck, the auxilliary solenoid closes and now the dead aux. battery will be charged by the alternator.
If you want the battery for increased cranking capacity all you need to do is add the second battery and battery tray, then wire the two batteries in parallel (+/+,-/- like hooking up jumper cables). If you use two identical batteries this effectively doubles your cranking capacity.
If you want it for increased cranking capacity AND be able to power something without worrying about killing the main battery, you'll need to add the auxilliary solenoid and wire it so its closed in BOTH start and run positions but open in the off position.
Here is the illustration from the parts catalog.
Click on the .pdf link to view.
Lead Driver
Joined: Mar 2010
Posts: 5,250
Likes: 11
From: West Virginia
btw extra batteries won't do anything for driving lights and ETC... if you are drawing near what your alternator can put out, it doesn't have the extra wattage/amperage to feed one battery. In that situation adding a second battery just adds to the strain on your alternator. If you are drawing more power than you are making, you need a bigger alternator.
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Laughing Gas
Joined: Aug 2007
Posts: 1,107
Likes: 32
From: Spokane, WA
While I am in no way a sponsor of theirs, you might want to Google "Hellroaring Technologies". They have a product that serves as a battery isolator that you can switch over from the secondary battery just serving as a power source for your trailer, to a cranking battery with the flip of a switch. They also claim that their isolator has a much more efficient power transfer rate than the typical diode isolators, with little to no bleedoff. I don't know if any of those claims are perfectly true, but I put one in Buford to see how it would work out. If you use a product like this, you'll need to upgrade the cables going to the secondary battery to be at least as beefy as the primary, so that it can be used as a cranking battery as well.
Anyway, thought I'd offer up another possible solution to the scenario. I haven't tested mine out yet, but it wired up easily enough (well, I was wiring the whole truck at the time, so it was just part of the job). Hope that helps a little.
Anyway, thought I'd offer up another possible solution to the scenario. I haven't tested mine out yet, but it wired up easily enough (well, I was wiring the whole truck at the time, so it was just part of the job). Hope that helps a little.
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Fleet Owner
Joined: Dec 2009
Posts: 20,678
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From: NorCal
Im wanting to put dual batteries in my 73 f250 HB with a 390 does anyone know if I need to do anything special under the hood to make it work or is it pretty basic?
:
A few webpages for your information:
NBC_Steve's installation: https://www.ford-trucks.com/forums/1...-with-pix.html
Dual Battery Installation
Dual batteries - FSB Forums
Elder User
Joined: Oct 2011
Posts: 842
Likes: 0
From: Palmyra
[quote=HIO Silver;12125422]It'd be awesome if ya could find some rust-free and newly refinished factory battery trays :
I think I have a couple 2 or 3 laying around on the self if ya can't find any in your area
:I think I have a couple 2 or 3 laying around on the self if ya can't find any in your area
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