I finally got around to installing my second Optima battery giving me a dual isolated battery system. The batteries are seperated by a high current relay that is closed when the engine is running so both batteries are charging. When I turn off the engine the relay opens and seperates the batteries so I can run electrical things and still have a battery to start the truck. I used the Blue Top Optima batteries, these are deep cycle gel filled batteries that work very well.

My current alternator is a only a 70 Amp but I will change that out later.

Quick note on grounding. Our generation of trucks have a really bad grounding method that causes malfunctioning turn signals, headlights and other electrical weirdness. I fixed my trucks grounding by replacing the high current ground from the (-) battery post on the main battery to the engine block. This is for your starter. I then added a ground strap from the (-) battery post of the main battery to the chassis. (See pic below.) I replaced the ground strap from the block to the chassis. (This is behind the carb on the intake manifold. I then added a ground strap from the bed to the frame and then added a grounding point for the rear electrical harness. No more problems!


Second (AUX) battery and high current relay mounting locations.



I make my own cables with 2 GA cable, wire loom and crimp on lugs



I crimp the lugs with "Whack-A-Lug" (Note hammer in the background)




I used all new rubber coated steel clamps after I installed the heat shrink and wire loom.



The cable routing along the back side of the engine compartment.




Clamping down the AUX battery. I'm not impressed with the "Universal" mounting hardware so I may change that out later.



The finished work.

 

Good work!

Someday I plan to do the same, so this is bookmarked now!

 

Never thought of running a relay that way, smart n simple. I have an isolator that will do the charging to the battery that needs it more. The P.O had them run together, still 12v but just larger capacity. I think that is why the old alt fried, I was always told to run a dual battery isolator to avoid that. Maybe keep an eye on that lil alt untill you upgrade, I don't think it would be a problem with a 3g... Still nicely done!

 

Thanks!

On my first truck (1972 F250 Ranger XLT) I had an isolator and I had nothing but problems with it. I got rid of the isolator and everything worked fine. That was 30 years ago. I find that the relay is a simple solution and always works. I have the same system on my 05 Suburban that has a 180 AMP altenator and a very heavy electrical load.

 

Thought I'd add on here what I did for my dual battery setup. For starters I hate aftermarket and stock battery boxes.stock platic top ones crack when overtorqued and aftermarket ones are flimsy. I'm pretty hard on my truck so I needed something that will last and hold. Heres what I built



Its 1/8 plate. The bottom box has 4 holes that bolt to the inner fender.

Next my dual battery setup is a painless solenoid switch rayted up to 250 amps.





It has a toggle switch that I mounted to my dash that has 3 positions.
Top: green light on and it will connect the two batterries together only when the ignition is turned on. turn off the key and they isolate each other so they cant drain themselves
Middle is only main battery all the time
Bottom: red light comes on and it is a overide that keeps the 2 batterries connected whether ignition is on or off.
I have the power wire to it on my aux battery so in case the main is dead I can switch the toggle to connect them together and fire it up and engage it to either the top or bottom toggle position and charge both.

 

Looks neat. Dumb question alert= what is the purpose of dual batteries for your setup? And, is that two vacuum reserve cans i see under your hood? My truck only came with one.

 

73 ford guy, you should consider building those battery boxes, I know I would be first in line to buy 2 of them. Sorry to get off topic guys.

 

I know so simple and it works right. The bottom angle tabs have a welded nut on the underside. I was going to make T handles to unscrew but this was cleaner.

I was thinking of moving the optima to the very rear underside, sideways as they can be mounted that way with no issue, also it would transfer weight over back wheels as this optima is the Big industrial version with largest reserve and heavy and also in the back on a tight trail I could back up to a dead vehicle and do a jump start.

 

Just to add an additional idea, here's a pic of my solution to the universal hold down. My rubber piece dry rotted and fell apart in about a year, so I used some 1" strap and made this, but kept all the other hardware in the kit.

 

I used the same painless relay kit for my dual battery setup, built a replacment panel to replace the ashtray. Used my bed for the batteries and custom optima hold-downs.





Love seeing all the different ideas, keep them coming!

 

Years ago I had a 77 4x4 that I set up the same way. It worked trouble free the whole time I had it. I will be doing the same thing on my current 78 after I get the Cummins set in. The regular battery isolators are a PITA................

 

I am also running dual batteries using a solenoid to connect them. Just make sure to use a continuous duty solenoid with high enough rating and not a starter solenoid.

My set up is similar to 73 Ford Guy's set up except I use a battery kill switch behind the grill and a two position (on/on) toggle switch on the dash. In position 1 the main battery is connected as per usual and the second battery connects through the solenoid via the key.

In position 2 on the toggle switch the solenoid is activated by the power of second battery. This allows me to still activate the solenoid and start the truck off of the second battery in case battery one was ever to go dead because I didnt use the kill switch and forgot the lights on or whatever. I also added an LED light when the toggle is in position 2 just to remind me to return it to position 1 otherwise the both batteries go dead if I were to leave the lights on.

 

Hey 77460Ford got any shots of the dash cluster. That is the look I want to achieve. Did you make it all yourself?

 

So not to hi-jack the thread you can see more dash pics in this link:

https://www.ford-trucks.com/forums/8...ld-thread.html

73 ford guy, some sweet battery boxes!

 

Hey thanks for the compliments guys! I never really thought too much about it but yeah they work very well. I have to actually be carefull on how tight I go on the bolts so I dont damage the battery tops...lol