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