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I was wondering how you would run 2 batterys. Keeping it on a 12 volte system.
My buddy will be runnig 2 optima yellow tops batterys. so if you know how to run them please let me know.
Thanks.

 
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Yeah I have been wondering this too, For my system im gonna be running 2 optima yellow tops also, I should upgrade my alternator too huh? Hey sorry for the thread hijack but any brands good for "performance" alternators? Im gonna be pushing close to 1000 watt rms, and ideas?

I figured it was + to + and - to - but I dont wanna screw it up.

 
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Bump!

 
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1kw rms isn't too much, your stock system should be able to handle it for the most part, it depends.

For two batteries, you can get an isolator to let you only drain from teh second battery, most useful for running the system with the engine off. It can also be useful just to wire the battery in parallel in the trunk, close to the amps.

http://www.bcae1.com/battiso.htm

 
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well see, my buddy is going to be running his sound system which is about a 1000 watts rms. plus, he is going to be running two compresiors now for his bags,before he was running only one.
he is also looking into putting a carputer in his car. so thats why we were woundering if we should run two batterys and not one. and if so how. thanks

 
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use an rv solenoid (not an isolator) to seperate the 2 batteries

rv solenoids are very efficient whereas isolators are not

 
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What would happen if I ran without an isolator or a RV solenoids, I saw a diagram on that site that said how to do it, so is there any downsides to it?

 
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Very true, You can trigger the solinoid from your ignition, so when the car is on both batterys get charged. When the car off is the batterys are seperated. I have two batterys for my system although Im am not running the solinoid, its the proper way.

 
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To answer your Q, I have done this on many vehicles the only down side to this is if one the batterys starts to die (wont hold charge anymore!) then it will kill the other, becuase the good battery will try to charge the dead one!. Now I have this in my old probe and I ran 4 deep cycles with a regular acid battery up front, never had a probelm but all batterys were brand new to begin with.

 
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but seriously you can use a dare I say a FORD! mustang or escort starter solinoid there 25.00 USD at any parts place!

 
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So if I got 2 brand new optimas I could just wire them positive to positive and the alternator would charge both or do both batterys need to have the alternator connected directly?

 
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they'll both charge.

 
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what he said^^^Like I said thats the way Im running my car right now,no problems. But if one of the batterys dies I wont know which one untill I yank it out and test it, just kind of pain in the butt.

 
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how you wire them together will be dependant on what kind of perforamnce you want, or what you want to do with your car. so the first question is, what do you want to do that warrants a second battery, or what do you want the second battery to allow you to do?

answer that, and then we can tell you the best way to wire them up

 
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Alright well I want the front battery to run the car, and its crap, and I want the second battery to run my... 2 12's, 2 450c viair compressors, and my speakers.

 
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then a diode isolator is really the only way its gonna happen. any other isolation or non-isolation method to wire them together will result in both batteries running everything. the rear will run the car, and the front will run your ocmpressors

 
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ok so say it didnt matter which battery did what, my main goal is just to have enough power to run everything with no more dimming headlights and other crap.

 
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alright, im not sure about the compressors, that might be an alternator fix. the only real way you will be able to determine that is by actually putting the batteries in and testing for dimmage.

certainly your audio system merely needs a cap or two or three to eliminate dimming.

I think your yellowtops will help for sure. They run at a higher voltage than standard batteries, so a voltage drop will result in less severe dimming. However, I personally think you will still get that minor dimming een with a pair of yellowtops if you are running compressors. they take LOTS of current!

I would almost think that due to the nature of the current draw, you would invariably be reverting to battery voltage when your compressors click on. so thats a tough call.

I wouldnt expect a fix, just a reduction operating a pair of yellowtops. and since dimming is your goal, you can simply wire the two batteries together in parrallel. no need for an isolator!

 
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Alright so I run the 2 batterys with 2 gauge wire connecting them? I figure the bigger the better.

 
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Yes the bigger the better, less resistence!