Isolator or relay for dual battery system???
 

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!

Isolator or relay for dual battery system???
 

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

0 - 4 gauge.

Sparkyyyyyyyyyyyyyyyy !!!!

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Isolator or relay for dual battery system???
 

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 :-X22

Isolator or relay for dual battery system???
 

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

Sparky :-X22

Isolator or relay for dual battery system???
 

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.

Isolator or relay for dual battery system???
 

[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.

Isolator or relay for dual battery system???
 

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

Isolator or relay for dual battery system???
 

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

Isolator or relay for dual battery system???
 

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 :-D
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 :-X22

Isolator or relay for dual battery system???
 

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

Isolator or relay for dual battery system???
 

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

Isolator or relay for dual battery system???
 

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

Isolator or relay for dual battery system???
 

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!

Isolator or relay for dual battery system???
 

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.

Isolator or relay for dual battery system???
 

>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!

Isolator or relay for dual battery system???
 

Isolator & relay?
 

BIG QUESTION! I have a 2 leg isolator. as follows
Battery 1 = Starting battery
Alt = Alternator
Battery 2 = Secondary battery


I have ALL my accessories on the second battery, and the starter itself on the main battery. Was wondering if i can put a large relay between connectors battery 1 and 2 on the isolator, and a toggle switch so when the second battery dies I can get a "Self jump" from the main battery to turn it over? I was just wondering whats the BEST setup for an isolator? I was told to put the starter on the battery under the hood, and accessory wire to second battery with all my other stuff. But if the second battery completly drains then I cannot start my car.. so would putting a relay between batttery 1 and 2 terminals on the isolator screw up the isolator? or would that be preferred? Someone help me, or email me at simbalage21a@gmail.com.. as i am completly confused about this? IdeAs?
Also respectivly have several amps, laptop and more.. always do stupid stuff like leave the lights on ect.. and want to prevent that.
240a Isolator installed.

Why can't you start your car if the second battery drains? Your primary battery starts the engine correct?

Vanner Battery Isolator 250 Amps "SELF JUMP"
 

I got the main accessory wire of the aspire ran to the second battery.. so the fuel pump, ect are on the second battery.. So In theory if the second battery has little juice.. the starter battery is full for cranking.. but say i leave the laptop on and its completly flat.. no start.. I have a big relay from ambulance and would like to be able to use a toggle to bridge the + of both together like a temp jump when its flat... but worry somehow this will mess up the internal diodes of the isolator..

PS THANKS FOR THE QUICK RESPONSE.. Outside right now messin with it.. to scare to just try it..
I just tied the MAIN accessory wire to the second battery so ALL my accessories were on the second bat (IE the wife leaves the headlights on she has a good starting battery)... Also I leave the laptop on alot which indeed does drain the battery.. if thats not possible... would a silinoid relay and a nother battery be best on the second so I can flip a switch to "Self jump" the flat battery? I wanna do this the best way possible. The isolator is eBay Motors: Vanner Battery Isolator 12/24VDC 250 Amps (item 260341071285 end time Feb-01-09 11:02:44 PST)

Idea
 

http://i43.tinypic.com/vr79ew.jpgwhats going on? why isnt it posting now? This is weird. anyways a pic is worth a thousand words! Why? because ALL my accessories are on second battery. I didnt wanna manually add them all. So with the fuel pump ect.. if the second battery goes flat I loose all accessoies. Would this image work without messing up the isolator?


Here are some of my vehicle diagrams

Fig1

Fig2

Fig3

PS: Thanks for the quick response!.. Images arent all what i have/or am using. The vanner is the isolator and relay resembles the one i have..

any takers?

You could try that, and it would probably work. If you did wire it that way, I would activate the solenoid you added with a momentary pushbutton that you could operate with your right hand, just enough time to jump it off. I would not leave it engaged all the time.

But I think it's unnecessary if you re-wired your electrical system. For the leaving the headlights on problem, I would buy a little cheap warning buzzer you can buy at JCWhitney. Then I would hook the truck back up as original on the 1st battery.

I would then hook 2nd battery for like you said accessories. By accessories I mean any high current loads or loads that you will be running with the engine off, such as your laptop. And for long life, the 2nd battery should be a marine or deep cycle type.

This is really how the isolator was made to be used. You need to consider all the circuits that the truck needs as one load and keep them all together on the 1st battery. All your added loads need to be on the 2nd battery. It's almost like putting the head unit of the stereo on the 1st battery, and putting the amplifier on the 2nd battery. By doing that, you lose the whole advantage of the isolator, since you are pulling off both batteries.

exactly my point. Why isolate the batteries IE playing the radio, if the main battery is used too while its on because is on acc (ignition) so I hooked the MAIN wire from battery that has all accessories to the second bat. But when its completly dead.. what good is a good starter battery without the fuel pump and other things that are on the same circuit? Any and all idea's are greatly appreciated. I was thinking momentary switch too, but dont want that relay to fry the isolator... just want all accessories on truck battery, and starting stuff on the main battery.. just am unable to get it to work.. I want alll or nothing..

Is the factory radio the only thing you want to use while the engine is off? I thought you would be having trouble playing the factory radio if you have a modern truck, with the door open and the buzzer buzzing with the key in the ignition.

So you are saying to leave everything on the main battery main wire wise, and manually adding my radio, cigar, and other circuits to the second battery? I mean how would one do the ign circuits like the radio ect... because they would still be on the starting battery! holy moly i am good at electonics but lost at this.. Its just confusing the theory is awsome. but you cannot that i see achive what i want. I can connect my inverter, amps, laptop load to second battery and that be cool.. but would rather all accessories be isolated from the starter and starting circuits.. Going out to cut the main again.. and try seeing which circuits needed with starter make it start...

nothing is factory.. 3 amps.. mp3 deck.. its connected in a mannor it comes on with the key.. as to my other gadgets too... radar.. laptop.. ect...

how about this? is there a 3 leg relay? but high amp? was thinking of using that.. like the little black ones but LARGER! that way I dont have to mess with isolator.. have it set up so when relay is off its using the back battery for all accessories. When you flip it on, it switches from back battery to the front battery for accessory.. because i've found if the back battery is flat.. and i disconnect the acc wire and connect to starter battery.. it will fire up!

This is one way you can have your cake and eat too. Install a switch in the power leg of the radio. Leave the memory wire hooked up to the primary battery so you will not lose the memory all the time. This switch would be single pole, double throw. It would select power from either the truck's wiring like you have it now, or the 2nd battery system.

So the switch would be the solution to the radio. The amps, and all the power ports will be hooked to the 2nd battery system. They make power ports you can buy and mount, so you could leave the stock ones alone if you wanted.

So all the accessories you want to run should be on the 2nd battery, and you will have to switch the radio head unit. Just like the memory being lost in the radio if you switch it all the time(so put it on the primary battery), I don't like the idea of switching the main power to the truck because of the computer for the engine. By the way, I don't know what year truck you have, you might not have a computer?

Removed! Double post. See page 3

ford aspire with JUMBO isolator.
 

PS: thanks for reading my boring post and helping out so much.

Aspire isolator help...
 

LOL. I wish it were a truck. Its a 1996 ford aspire. LMAO! anyways ran everything from 6aga to 2aga. accessory wire is still on the 6awg. I like having everything on the 2nd battery. and having the starter battery with nothing but the starter. Because I am always putting the key in to use some accessory. lighter, radio, tvs, laptop ect.. something (i havent figured out what) keeps killing my main battery.. which is why i decided to put the second battery. maybe too many memory items, maybe the alarm being it has the option for 2 way paging who knows. i will take pictures of my rewiring and post. if the second battery is just weak.. then it will fire up well because the primary battery has nothing on it, so it has the cranking amps I want (especially being its been so cold out)... I went ahead purposly and left my headlights on.. killing the 2nd battery. then tried starting it. Wouldnt go.. disconnected the main accessory wire, and tapped it on the main battery, and it fired up. do they make a double throw relay, or a large switch capable of switching my main accessory like you mentioned doing with the radio?

any ideas?
 

Well I tried it again. Use them black 40amp relays. Between the main accessory wire and the battery under the hood.. left headlights on. Went to crank when it was dead! no start. Pushed the momentary button while holding button it started! its this ok do? or will bypassing isolator eventually screw it up?

Isolator installation...More problems PLZ help
 

Someone PLZ take a look at the diagram below. For some reason my second battery doesnt seem to be charging as good as the starting battery. If you notice the red circles thats where my question lies... where it shows the main fuse is where the big circle bolt was connected to the car. I Removed that, and ran a wire from that DIRECTLY to the isolators alternator input.. but the other one comming off the harnass runs to a big fuse labeled head.. which when pulled makes the headlights go out.. The diagram shows it connecting in junction with the main.. and the smaller one going for the charge idiot light.. My question should the red one be drawn to the ALT leg on the isolator with the main power wire (bolt one) or what? I never installed an isolator before.. But I have a total of three wires. and this application is tricky because its a ford.. but mazda makes the engine!
http://i41.tinypic.com/qq921l.jpg

Isolator Expert Plz Read!!!
 

Above post Plz Read:
Added info:
Checked the steps outlined online for general isolator testing.

Running I have around 14v on second battery.. And 14.9 on battery 1. ALT is pushing 15.4 it seems as if both batteries are getting charge. So I think the back one is dying, But still want to know if the red wire from my last post should stay connected to the fuse block under the hood, or go with the battery output that was moved to the ALT input on this vanner isolator. Also read that scottych (however you spell it) diodes in this isolator are best.. I got it out of an ambulance so assuming this is this the best possible setup?

Hey some nuckle head was arguing with me over this topic saying relays are better so I found this old post on google.. I have resolved the issue and have all the oem stuff on the front battery and pc,amps ect on the back battery... hasnt failed me yet and if in the even i need a "Self jump" i use the relay to temporarly bridge both batteries together.. So awsome to be fishing and listen to the radio and ppl wonder why i never have to start my car .. radio goes off.. you hear "uh oh" he is gonna need a jump.. hear a click (more like a pound) and Vrrrrrrrrrrrrrrrrrrrmmmmmmmmmmm LOL


Thanks you all for kind regards on getting me setup with this foolproof setup.. 2 yellow tops later its PurFect!

I been hanging out at fordaspire.com where they too are amazed at this car :)

hi guys, hows all ya's day going?
quick question since were on the topic of isolators.
i have a 2000 explorer xls 4x4 with the 4.0 ohv 6cylender. i recently got a NOCO igd140hp isolator and have it installed underhood, everything is all nice and what have you. well ran my cable from alt to inline fuse beside fuse box underhood, then from there to my center (alt) post on isolator. front batt post to front batt and so on. now my only issue is, i have no power whats so ever. but testin my battery wit DMM and its reading 12.4v well within proper voltage. now the only post on my iso is the tiny one for like a 'hot' line i wanna think its for, but wasnt sure if i was to have it hooked up or not?
thanks in advance:-jammin

well i just figured out my issue..a true DUH! moment lol
from alt to alt on isolator..battery 1 to fuse, fuse to battery.
im living up to my blonde hair lol

old Thread, But now I have an explorer
 

So I still have the vanner isolator. I have a 94 ford explorer and this brings this thread back to mind. I have noticed on a few cars (the aspire, and a Volvo 240 dl) when putting the isolator between the main leg of the isolator the alternator will not charge, or it kills the alternator. Does anyone know why? I was told some need this voltage to travel both ways so the alternator can read the battery correctly. On of the cars it worked but I had to rev the engine past 2K before it started to charge. With this ford explorer can I directly mount this isolator? I plan to do the push button to jump start. I was at walmart today with just the main battery and it froze within the time I was shopping. So we froze for about 30 min because they don't offer boost anymore (maybe lawsuit) anyways can someone confirm this type working with this isolator? I have used relay type before with success, but found the engaging of the relay when the aux battery is dead shortens the life of the batteries.. Any help would be appreciated.

I have ran into this. using the wires you have connected to the isolator connect them all together and see if it works, if so you have a bad isolator.