Dual Battery System - Ford Truck Enthusiasts Forums

1973 - 1979 F-100 & Larger F-Series Trucks Discuss the Dentsides Ford Truck

Dual Battery System

Old 06-18-1999, 01:48 PM
ray is offline
Senior User
Join Date: Jun 1999
Posts: 144
ray is starting off with a positive reputation.
Dual Battery System

If you want to add the second battery to gain additional storage the batteries can be added in parallel. That means to mount the second battery and run cables from to and - to -.
If you want to have the second battery where you can "pull on it" without draining your truck starting battery then you need an isolator. These can be purchased at most Recreation Vehicle supply houses. I thing JC Whitney has them also.
If you install a second battery it should be the same age and condition as the original; Best bet two new batteries. Hope this helps.
Old 06-19-1999, 12:18 PM
fordmando is offline
Senior User
Join Date: Jun 1999
Location: Greenville USA
Posts: 265
fordmando is starting off with a positive reputation.
Dual Battery System

Or you can connect the batteries with a heavy duty relay. Wrangler Power Products in Prescott, Arizona; sells a relay, three position switch and all wiring for about $100. Switch lets you connect both batteries when running (for normal use), all the time (jump start yourself), or not at all (If there is a problem with the batteries).

Also marine supply houses sell manual switch for use in boats, they will work fine in a car, but you have to turn off the car to turn the dial and switch modes, or else it can fry your alternator.
Old 06-19-1999, 06:37 PM
sparky's Avatar
sparky is offline
Posting Guru
Join Date: Jun 1999
Location: Comox Valley, Canada
Posts: 2,415
sparky is gaining momentum as a positive member of FTE.sparky is gaining momentum as a positive member of FTE.
Dual Battery System

You could always just put a start relay ( it can handle all the current the battery can put out) in the positive line that connects the two batteries, then you could add a switch and wiring to close the relay when you want to charge the 2nd battery.
When the switch is off the batteries are separate and you can use the 2nd battery for accessories with the truck off and not worry about killing the main battery.
Simple to do and cheap. Good luck on whatever you decide.
Old 06-21-1999, 05:56 PM
Les is offline
New User
Join Date: Jun 1999
Posts: 8
Les is starting off with a positive reputation.
Dual Battery System

>I have a 76' F-250 and would
>like to add a dual battery
>system. I was wonder would
>it would take to hook a
>system up to have the alternator
>charge both batteries. Can any
>one give me some direction.

Yep. go for it !
A second alternator and battery installation is easier than buying special dual charge black boxes etc. I have a second alt running of the A/C spare pulley and the biggest battery I could put in the left inner guard I could buy. Since the batteries are independant devices, there is no need to match batteries for performance or size. My set up has been operational for 13 years so I think I have passed the beta test stage.
A ford starter solenoid and a dash mounted horn swith is used for 'joining' the batteries for a flat battery start or at those cold starts in about 1/2 revolution. The seconds batery is used for powering the driving lights at other times. The truck has about 760watts draw on H/beam. If you need Further info E-mail me direct. Good luck
Old 06-21-1999, 06:21 PM
rick's Avatar
rick is offline
Senior User
Join Date: Jun 1999
Posts: 288
rick is starting off with a positive reputation.
Dual Battery System

Related Topics
Thread Starter
Last Post
1999 - 2003 7.3L Power Stroke Diesel
08-16-2016 08:21 PM
1968-2013 Full Size Vans
06-07-2016 10:37 PM
1999 - 2003 7.3L Power Stroke Diesel
01-29-2014 03:55 PM
1999 to 2016 Super Duty
03-28-2008 10:01 AM
Electrical Systems/Wiring
08-17-2007 12:58 PM

Thread Tools
Search this Thread
Quick Reply: Dual Battery System

Contact Us About Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.