I was wondering if someone can tell me what the difference is between installing a battery isolator and just installing a relay between the batteries on a dual battery system. I'm getting ready to put one on my bronco. In the past I've used an isolator, but Wrangler NW and Painless Wiring sell these relay or solinoid kits that seem to do the same thing as an isolator. The relays of course allow you to "jump" your primary battery from your secondary if need be. Anybody know why I can't just install an isolator and then a cheap Ford starter solinoid between the two to "jump" the primary if I need to? Thanks!

 

Sure,AFAIK There's no reason why Not ?
The wire would have to be fairly large though.

0 - 4 gauge.

Sparkyyyyyyyyyyyyyyyy !!!!

Where are you?



Dennis https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1733&.jpg



Please Don't Ask Me Any Tough Questions As:
"I'm Saving My Memory For When I Develop Alzheimer's"


78 F-150 429CJ,Silver
w/Explorer Pkge.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon

 

Isolators are the better choice IMHO. They keep the two batteries separate, so if one goes dead it doesnt take the other one down with it. Relays can accomplish the same thing but have more moving parts so hence are more prone to failure and the batteries are actually electrically connected to each other when charging. With an isloator they are never connected together, they are protected from each other by "big honking diodes" or something very similar
If you add a relay, I would go with a starter relay. It will handle the power of a "jump start" and is fairly cheap. I would also go with a momentary switch to close the relay. That way you wont forget and leave it on thus bypassing the isolator.
I guess one of the the main differences is the price. Relays are about $15Cdn while isolators run around $80Cdn.

Sparky

 

I would have been quicker mil1ion but I am a slow typer

Sparky

 

Wow, I thought the web site had blown a fuse when I got 3 replies in as many minutes. Thanks for the info Sparky. That's a good idea on the momentary switch also.

 

[updated:LAST EDITED ON 14-Feb-02 AT 04:13 PM (EST)]Go for the isolator you will not regret it. I've got one in my truck and it works perfectly. And the wiring your talking about will work just fine. I've got my secondary battery wired to a starter relay then to my main relay. I've got it set up so that all I have to do is flip a switch in the cab and my second batt is giving my main batt a jump start. Also i would go with just a regular switch so that if your alt gives out for what ever reason you have more battery power to get you home.

 

Thanks 72 Ford, that's another good idea about the switch. I can see your point. Ben

 

Sparky, got another question for you. If I have a 130 amp alternator do I need a 130 amp isolator or can I go with something like a 90 amp? Thanks

 

That depends on a few things. The alternator is capable of putting out 130amps but it doesnt put it out unless you need it. So it will depend on what loads you have on the alternator.
If you draw more current than the isolator is rated at you will "blow" the diodes, if it is in fact diodes inside I do not really know but I think diodes are probably in them never cut one apart....yet
If your alternator is putting out 130 amps but the load is split between the two batteries charging circuits, say 65 amps each battery, then a 90 amp rated isolator would be fine.
As I said it all depends..... mainly on how the electrical circuits in your truck are split up. If possible run the high demand loads, like winches, lights, power seats, microwaves, hot tubs, etc evenly split between the batteries.

Sparky

 

Thanks! how'd you know I had a hot tub in my Bronco? haha

 

Just one more thought,use the Isolator for the charging, Solenoids as the Ford starter solenoid is ment for intermittent use, (more moving parts as Sparky noted) not continuous use as using for a charging circuit, had repaired a Motorhome with a circuit problem to find that it had from the Factory in this Ford E-van chassis a starter Solenoid that stuck and fried the wiring back to the refridgerator, cost for repairs was around 1000 bucks, use the Isolator. Electric1

 

If you have the time, you may want to check out "Hellroaring Technologies". Their battery isolation system is excellent. It's not cheap, around $150. But the function may be worth it.

Anyway, it cant hurt to visit their website. its educational
www.hellroaring.com

good luck

 

Thanks, I looked at the Hellroaring site and the "isolator" they have seems to just be a solid-state relay. It connects both batteries together when the truck's running. I like the true isolator idea because it keep my deep cycle and starting battery separated but charged at all times. Thanks!

 

A common starter solenoid has a 3.5~4 ohm coil, a "contiouous duty" solenoid, like in a forklift, has a 18 ohm coil. Any parts store can get them, just be specific. They look identical. Works great for dual battery isolation.

 

>A common starter solenoid has a 3.5~4 ohm coil, a "contiouous duty" solenoid, like in a forklift, has a 18 ohm coil. Any parts store can get them, just be specific. They look identical. Works great for dual battery isolation. <

You MUST use the continuous duty relay if you want to actually use the second battery to power the vehicle [bad alternator]. Otherwise the relay coil will overheat and fry. Either type of relay can be used to "jump" the main battery from the aux.

HOWEVER!!!!

To keep both batteries charged properly you MUST use a battery isolator! If you do not, one battery will discharge the other over time, or one will fail to charge, due to differences that develop in their electrochemical makeup, even if they are exactly the same to start! If you are using a deep cycle battery for the aux the problem is magnified. Or if you start out with mismatched batteries [very bad idea] the system will fail rapidly. Ford used to use the continuous duty relay setup as an OEM solution because it was cheap and it would usually last thru a 1 year warranty period with new batteries. It never did work for long, and could not work due to battery chemistry problems. If you use an isolator you can use different types of batteries in the system, or even a new and old(er) one.

ALWAYS USE AN ISOLATOR! You can use the proper relay to bypass the isolator for those high current needs.


over!