Dual Battery

[Bennett2043]

Anyone know how to wire up a dual battery?

Thanks
Ben

 

[got wake?]

do a search. i've posted about it many times. but here's the run down:

DO NOT DO IT!!!!!!!!!!!!

 

[pr5owner]

hey what wasn't the question, you wire up dual batteries in parrallel, + to + and - to - thats it! SUPA SIMPLE!

 

[got wake?]

then pop, fizzle, no more batteries

 

[pr5owner]

then pop, fizzle, no more batteries

that is still not the answer to his question LOL (headshake

 

[Bennett2043]

Why pop fizzle?!?

I was thinking about running dual optimas in parallel. Did you use a isolator?

Ben

 

[chuyler1]

Have you upgraded your alternator??? If not, do that first.

 

[Bennett2043]

My alternator should be able to handle it, since its a 136 amp. But this summer I will be putting in a 200 amp.

 

[got wake?]

Why pop fizzle?!?

I was thinking about running dual optimas in parallel. Did you use a isolator?

Ben

well not really pop fizzle, but you will kill both the batteries if not done exactly right, and even when done right you still risk both batteries dying very prematurely.

if you are running more than one battery, you have to use an isolator. people will say you can just get 2 identical batteries and be fine, but that is BS. it just takes longer to kill them. the problem is the resistance in the wire and the batteries. technically if you were to run 2 identical batteries with the EXACT same internal resistance you would be ok, as long as you have the exact same wire lengths going to each battery from the alternator. so if you have one battery up front and one in the trunk, you'd have to have a 16 ft coil of wire in your engine bay, so that there is not a difference in resistance to the batteries. course none of that really matters, since you will NEVER achieve perfectly matched resistance. heat will come into play and mess it all up. once one has different resistance than the other, it constantly drains from the other battery. then they reverse the cycle while the other that supplied the power is now drawing it. that goes on and on and on, till you can't even start your car.

beyond just the problems with the resistance is that the alternator cannot supply enough current to keep the battery operating properly. each battery is an added load to your alternator, and as such will require more amps just to keep them in good condition. with a high powered system, such as my current 1,900 watt setup, my alternator has no way in hell of supplying the necessary 150 amps to run my system. to maintain my battery i don't crank the system for very long with the car running, i NEVER play it with the car off, and i trickle charge my battery every week or so.

so back to my original statement, do a search. i've discussed this in more detail before on here. my buddy owns a battery and alternator shop, and i've tried a dual battery setup in my car, so yeah, i know what i'm talking about

 

[got wake?]

My alternator should be able to handle it, since its a 136 amp. But this summer I will be putting in a 200 amp.

be VERY wary of high output alts. they are known for putting out very little power at idle i've heard many don't even put out half their rated power. that's why i'm having my friend custom build me one that puts out 160 amps at idle and over 200 at 2k rpms.

 

[Bennett2043]

Here's what I got right now.

136 amp alternator, puts like 80 amps at idle.
My new alternator that I am getting will do 100 amps at idle, and 200 when under way.

Two Yellow Top Optimas and they both fit under the hood, so there won't be a huge length of wire, It is going to be like 4 feet in wire at most and I can use a any size wire I want, cause I am not going through a firewall.

What about a system like this: http://www.hellroaring.com/bic75300.htm ?
http://www.hellroaring.com/audio.htm another link there..

"It automatically combines your backup battery to your charge system only when it is charging. It automatically disconnects your backup battery from your system when there is no charge voltage."

I am doing a search under your username as we speak to find more out.

Thanks
Bennett

 

[servoeyes]

you can get battery isolators from places like sounddomain.com and even thezeb.com should have them. I don't know the specifics of the whole process, but I'm sure it's not too complex. It just sounds a little tricky...you're really just adding another *big* thing for your electrical system to charge. Could be good, could be bad...

 

[Bennett2043]

I did a search under your name, but couldn't find anything.

There is got to be a proper way to do this. How do Ford diesel trucks do it?

 

[Rider69]

I used a battery Isolater in an older vehicle (91 BMW) and never had problems with charging. Basically the isolator keeps the batteries seperated and allows one to charge while the other one doesn't. SO the Alt only still charges one battery at a time. With a HO alt, you should have no problems.

 

[pr5owner]

why not just a big batt and big alt?

 

[smithers_0990]

Why do you have your Location set as IL? We all know you live 20 min away from me.

This might help out the kind people of this forum.

The vehicle is a 2002 Jeep Liberty. It has an ungodly ammount of lights along with a decent system.
He will be the first person (that we know of) to run a dual battery setup in a Liberty.

His uncle fabracated a very nice battery tray for him to use. Right now he is trying to decide weather or not to go with the another yellow top and run them parallel or to get a isolator kit.

Did I get the jist of situation Ben?

Please post pics of the lighting system so the forum members know what they are dealing with.

 

[1sty]

The best way to get idle output from an alternator seems to be to use a factory built unit. I had a monster AC delco in my MP3. That beast was rated to 180 amps and tested to 120 amps at idle. However that load that requires 120 amp will crash the idle. With my JL 1000/1 firing I could almost stall the car as it didn't have enough power to spin that beast of an alternator.

 

[Bennett2043]

 

[got wake?]

Please post pics of the lighting system so the forum members know what they are dealing with.

bah, we don't need no stinking pics(chair) current draw is all that is important. and since you are dealing with a constant draw from lights, and not the duty load of a huge stereo system that is constantly changing it's current demands, it's a slightly different ball game.

so let's start over. what is the total current draw of all the extra lights, ie not the stock headlights? do you turn on your lights with the jeep off a lot? if so, WHY?

the reason why ford diesel trucks, and any other vehicle that comes with multiple batteries can do it is that the reason why they have multiple batteries is for starting the vehicle, and that's it. the only time the voltage is low is during cranking. put in a large system or add a bunch of amp hungry accessories, and you will kill the batteries in a factory multi battery setup. with extremely high torque engines you have to have MUCH higher cranking amps to turn the engine over, and with diesels you might have to turn it over quite a few times to get it running. but once it's running, there is no current being drawn from the batteries, they are only charging. look at tractors with 4 of the biggest batteries you can find. they need the high cranking amps that you get from multiple batteries. when you wire 2 batteries in parallel you keep the voltage the same, but double the cranking amps. that's why in a lot of army equipment they use four 12 volt batteries. 2 of them together wired in series to get a 24 volt system, then the 2 pairs run in parallel to double the cranking amps.

the ONLY reason to add a second battery is for more CCA's, and for more reserve capacity with the car off. other than that they will hurt you more than help you.

 

[Bennett2043]

The main reason I need a dual battery setup is to run my 2000 watt continous power inverter and a single battery is not going to last very long. SO I got two yellow top optimas to help me out. It can draw from anywhere from 1.5 amp to 120 amps continous depending what I am running off it. I am really thinking of just wiring them up in parrallel, since I believe using a isolator will make matter worse, since the moment the isolater reconnects to the other battery there will be a massive surge, as compared without using a isolater the batteries will "average" them selves together, assuming I use big enough cables.

Bennett

bah, we don't need no stinking pics(chair) current draw is all that is important. and since you are dealing with a constant draw from lights, and not the duty load of a huge stereo system that is constantly changing it's current demands, it's a slightly different ball game.

so let's start over. what is the total current draw of all the extra lights, ie not the stock headlights? do you turn on your lights with the jeep off a lot? if so, WHY?

the reason why ford diesel trucks, and any other vehicle that comes with multiple batteries can do it is that the reason why they have multiple batteries is for starting the vehicle, and that's it. the only time the voltage is low is during cranking. put in a large system or add a bunch of amp hungry accessories, and you will kill the batteries in a factory multi battery setup. with extremely high torque engines you have to have MUCH higher cranking amps to turn the engine over, and with diesels you might have to turn it over quite a few times to get it running. but once it's running, there is no current being drawn from the batteries, they are only charging. look at tractors with 4 of the biggest batteries you can find. they need the high cranking amps that you get from multiple batteries. when you wire 2 batteries in parallel you keep the voltage the same, but double the cranking amps. that's why in a lot of army equipment they use four 12 volt batteries. 2 of them together wired in series to get a 24 volt system, then the 2 pairs run in parallel to double the cranking amps.

the ONLY reason to add a second battery is for more CCA's, and for more reserve capacity with the car off. other than that they will hurt you more than help you.