Dual batteries

[Maurice Evans]

My 2 cents, add a 200a isolator between the two batteries. That way if leave radio on, door open, or any other reason to drain a battery, it will only drain one battery and second will still be good to start your truck! When engine is running the alternator will charge and use both batteries, it's only when engine is off that it only uses one battery, cheap safety measure! I use similar setup in stereo applications Sonu can sit around fire with radio going for hours and still know your truck will start even after waaay too many beers out in the woods lol.

What 200 amp isolator do you reccommend?

 

[Ehall8702]

What 200 amp isolator do you reccommend?

https://www.ebay.com/itm/143930759969

That's my go to, never really had any issues with em...have melted one before but it was taking 350a from the alternator nd was fine for quite a while lol.

 

[SUBURBAN5]

https://www.ebay.com/itm/143930759969

That's my go to, never really had any issues with em...have melted one before but it was taking 350a from the alternator nd was fine for quite a while lol.

Dumb question how would you wire it between the batteries?

 

[Nad_Yvalhosert]

The isolator goes between the positive battery cable from the aux battery to the primary battery.

So, leave the first battery hooked up as the factory wired it.
Install the second one with the ground wires to the engine and fender. (Like the factory did) The positive cable goes to the isolator, then to the first battery positive terminal.

My '00 Denali (without dual batteries) has a factory power point on the passenger side of the radiator fan shround. It's got 2 battery cables, a short one from the primary battery and a line from the alternator on one side. The other side goes across the top of the shroud, to the PCM. (Good place for me to tie in a secondary battery in the future)
The radiator should be a good place to mount your isolator. That way it's not gonna short out on the metal anywhere.

 

[redshift]

What 200 amp isolator do you reccommend?

Please... consider using a heavy duty CONTACTOR rather than an isolator. I had a really nice truck that I'd just dumped $15k into burn to the ground due to a faulty isolator that started an engine compartment fire while the vehicle was unattended, many hours after parking it. It was a very expensive Phoenix Gold model, carefully installed, with a current rating well above my intended usage.

The cheap/easy way to go about this is to use the extremely common Ford standalone starter solenoid. But there are higher end more expensive contactors out there if you prefer.

You can reap all the same benefits of using an isolator without the voltage drop drawbacks or the inherent risk of failure/meltdown/fire when using high current diodes that are likely sourced pretty cheaply these days.

 

[Supercharged111]

Please... consider using a heavy duty CONTACTOR rather than an isolator. I had a really nice truck that I'd just dumped $15k into burn to the ground due to a faulty isolator that started an engine compartment fire while the vehicle was unattended, many hours after parking it. It was a very expensive Phoenix Gold model, carefully installed, with a current rating well above my intended usage.

The cheap/easy way to go about this is to use the extremely common Ford standalone starter solenoid. But there are higher end more expensive contactors out there if you prefer.

You can reap all the same benefits of using an isolator without the voltage drop drawbacks or the inherent risk of failure/meltdown/fire when using high current diodes that are likely sourced pretty cheaply these days.

If a starter solenoid meets the definition of contactor, I'd say no to that as well. I used a starter solenoid as a fan relay and it didn't last long at all. I guess they're no good for continuous use.

 

[mr_josh]

If a starter solenoid meets the definition of contactor, I'd say no to that as well. I used a starter solenoid as a fan relay and it didn't last long at all. I guess they're no good for continuous use.

There are contactors that look essentially the same as the good old Ford fender mount starter relay but are designed for continuous duty.

Real common when you need to isolate an RV / trailer battery from your tow vehicle battery via ignition switch.

 

[Gramps]

The ford starter relay is not a continuous duty part, however there are some that are and they look very similar and many people confuse them. Monday when I get back to work I have a cheat sheet with part numbers and pictures along with specs on those.

 

[Ehall8702]

Please... consider using a heavy duty CONTACTOR rather than an isolator. I had a really nice truck that I'd just dumped $15k into burn to the ground due to a faulty isolator that started an engine compartment fire while the vehicle was unattended, many hours after parking it. It was a very expensive Phoenix Gold model, carefully installed, with a current rating well above my intended usage.

The cheap/easy way to go about this is to use the extremely common Ford standalone starter solenoid. But there are higher end more expensive contactors out there if you prefer.

You can reap all the same benefits of using an isolator without the voltage drop drawbacks or the inherent risk of failure/meltdown/fire when using high current diodes that are likely sourced pretty cheaply these days.

And on the contrary I've had ford starter relays melt down on the side of the highway and actually had to piss on it to put it out cause we were traveling. We use em for plow setups up here and more often than not they stick closed or melt terminals off. You want a serious one, get ahold of boss snowplow and get one of thier isolators, they can be mounted in an orientation and and are heavily over rated. The ford ones you can only mount them vertical or they WILL stick. I've been installing for over 25 years and can only think of 3 or 4 stuck isolators I've put in, I only use pac or stinger stuff , the ford ones I've put in were usually brought by customer or I've used em on my stuff since Im way up in middle of nowhere and needed one right away and that's what u can get from parts store. Ultimatly it's personally preference tho.

 

[Ehall8702]

Dumb question how would you wire it between the batteries?

Like the post after ur says between batteries on fan shroud, I tap off the exciter wire on the alternator to turn the isolator on , you could also use a toggle switch if you wanted...that way u can make sure only one battery drawing when engine not running, but is same with exciter wire off alternator.