Dual Battery Setup

Any tips on this deal ?

I have to much **** going on between the 8 lights , winch , audio amps , and CB amps ect .. So im going to a dual battery set up .

Things I have gotten or ordered ... a battery tray from a 2007 CTD , two identical 1000 cca battery's , and a 200 amp isolator . Figured my alternator now is 160 amp so a 200 max isolator will be just fine.

NOW the question how to hook it all up ?

Im thinking .. from the isolator hook post one to positive of bat one then post two from isolator to positive post on second battery . Then middle post off isolator to alternator ? and on second bat ground ?


Does this sound right ??

Two positive posts from the batteries, one is ground and the other is any source that shows 12v when the key is in the crank and run position but shows zero when the vehicle is off.
This is how the isolator knows when to allow for a connection between the two batteries to exist and to cut the connection when the vehicle is off, so the batteries do not drain on each other...

Found someone who did this to a 2nd gen ram. Couldn't be too much different.

Just buy the 2500 second battery tray for the 3rd gen. And follow the rest?

There are two ways. I did mine without an isolator simply because I would never have much key-off run time. If you do it with no isolator then simply run (+) from one battery to the other and ground from both batteries to frame or block. Mine go to both.

If you are running the isolator then the whole concept here is to separate the batteries when the key is off but tie them together when the key is on. An isolator is basically a high amp relay. You have a relay coil that requires very little power to close the contacts and you have the contacts themselves which tie together or separate the batteries.

So with the isolator you should have something similar to this, a ground terminal (could also be just a isolator chassis ground), a switched 12v post and two battery posts.

So ground is simple. No need to explain that. The switched 12v post is a just like an amp or stereo 12v switched power source. Find something from the fuse box or ignition harness for 12v only when the key is on.

The two battery posts are simple. Put the (+) from one battery to one post and the other battery's (+) to the other.

So this is how it happens, when you flip the key, 12v from the main battery energizes the relay coil in the isolator and closes the contacts and ties both batteries together. When they key is off, the contacts are open and the batteries are separate? Make sense right? Good.

Now if you completely drain the main battery while out fishing or jamming or whatever, there may not be enough amps and voltage to crank the starter, but there is enough to close the relay coil to tie the other battery in and give enough juice to start up and run.

I have pictures of my dual setup in my signature link. If you have any issues just LMK.

Yay Weedahoe!!! :********:

I always just thought about skipping the isolator, and wiring both batteries in parallel. So that they each share the load. Basically still having +12 volts, but it'll last twice as long. But this sounds cool too!

Wow! I just spent 20 minutes looking at all of your gallery/mod pic. Extremely impressive!

My RV was setup as a main bat and a accessory (Aux) battery set of two in parellel. The engine ran off the Main and everything else including the inverter ran off the other. When the engine was running it would automatically connect the Aux batteries to the alternater for charging. The Aux batteries could not be used to start the engine. But the main battery would remain isolated during times when parked while camping so was available (fresh) when the time came to start the engine. Your setup I see with your add-on items such as *****, lights and amp wired to a seperate power panel that is powered only from the Aux battery, leaving the Main battery for what it currently does, ie, running the normal truck stuff. The 200A isolator is fine for charging but won't carry the current for a starter. So, Main battery to start the engine. Aux battery to to run accessories. Good luck..

GoMangoMan said:

Wow! I just spent 20 minutes looking at all of your gallery/mod pic. Extremely impressive!

Click to expand...

THX bud. Always more to come.

As soon as I saw the title, I knew Weed would be the man to answer it!

Weed, what do you think about Greg's statement that the 200a isolator won't carry the load for the starter?

I knew Weed would be the man , so I Pm'd him ..lol

Thanks for popping in Weed !

Now Im on the fence ? Do I really need a isolator . I just want to take the load of my starting battery , have one for all my lights ,amps and winch . I almost never turn anything on without the truck on .

Why not run a $40 isolator? Seems like cheap insurance.

This one work ?

NEW 200 AMP DUAL MULTI TWO BATTERY ISOLATOR - eBay (item 140486076890 end time Apr-02-11 11:56:07 PDT)


So with this one ... from the isolator run + to bat 1 and two . ground each bat , and run from the isolator a + from the ALT ?

So do I disconnect the line from bat one to the ALT?

The question here is from stock do I need to disconnect the pos that goes to the ALT now and just run it like this ? And I asume my alt is a 160 amp . Do i need a 160 amp isolator or will a 200 also work ?

That looks like it would do it.

GoMangoMan said:

Wow! I just spent 20 minutes looking at all of your gallery/mod pic. Extremely impressive!

Click to expand...

Damn straight...


im glad you asked about this dave, my lights are dimming and i saw my uncles ctd with the dual battery setup and got interested

Leaving the auto place now 350 dollars later I have 2 new batterys with 880 cc amps each. Called dodge ran my vin I have a 136 amp alt. So what isolator to go with.

Like i said, I didnt bother with an isolator only because I knew I was not going to have hours or use with the key off and didnt feel i needed it. I have done the Big 3 with 0/1 welding cable and my amps are fed with 0/2. All of that is kinda overkill but I had it all laying around. I bought lugs for the ends and had the tools at work to compress them.

Stinger also make a good isolator and I think it is a 200 amp. About the same price as the one above though i think. Around $80 or so. But as you said, do you need it? My e-fan is wired to run with the key off so after driving and shutting off the engine it continues to cool.

Im running my e-fan, 2 sets of HIDs, 2 sets of 100w Hellas, a Viair 380C air compressor, a power inverter, Xbox 360, 5 screens and getting ready to add a truck-puter with a special dedicated 12v power supply.

ive got two 1000 CA / 850 CCA batteries and a stock 136A alt.

Hope all this helps.

Weed ? What is the sole purpose of the isolator ?

Since I dont run stuff with the truck not running I think I will skip the isolator .

So I just mount the battery's leave the stock cables alone ? jumper the + sides together and ground them both ?

It cant be that easy ? Both will charge off the ALT at the same rate ?

ramhunter9 said:

Weed ? What is the sole purpose of the isolator ?

Since I dont run stuff with the truck not running I think I will skip the isolator .

So I just mount the battery's leave the stock cables alone ? jumper the + sides together and ground them both ?

It cant be that easy ? Both will charge off the ALT at the same rate ?

Click to expand...

Dave, the isolator allows you to run the Aux battery down and still have the main battery available to start the truck at the end of the day. Wiring the batteries together without the isolator basically makes one big battery and there is no reserve to start the truck if they are run down. i would use the isolator and connect all my add-on electrical stuff to the Aux battery. This way the truck can be started at the end of a hard day..

If you need any reference pics, send me a PM; mines got the dual battery setup.