dual battery setup

[bandikook]

lets say i have an optima and i want to run two because of lighting and other drains on the battery. If i just connect a postitive from battery A to battery B and same with a ground, will my alternature chargebattery B too. If not, how do you set up a duel battery setup.

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[michael]

You should really pick up a battery isolator.....most RV stores have them.

Michael <A target="_blank" HREF=http://mkparker.com/goose>mkparker.com/goose</A>

[hoeker]

the way he's talking about hooking it up will work fine with no isolator needed. an isolator is for instances like winching, the winch is hooked to it's own battery so the battery needed for the engine isn't run down winching the truck. the vehicle can then start and charge both batteries through the isolator.
either system works fine, it just depends on your needs. if you just want extra capacity for lights, and they won't be on when the truck isn't running, the way you described is fine. if you like to sit by the campfire with your radio on until you pass out, hook the radio up to the second battery and get an isolator.

<A target="_blank" HREF=http://www.rosshoek.com>www.rosshoek.com</A>

Some are born great, some achieve greatness,
and some have greatness thrust upon them.

[Kritter]

"if you like to sit by the campfire with your radio on until you pass out"

Glad I am not the only one who does that!

Kris
<A target="_blank" HREF=http://www.barneysprecision.com/fabproducts.htm> Fab Parts</A>

[hoeker]

not that i do that, just heard it happens sometimes. lol

<A target="_blank" HREF=http://www.rosshoek.com>www.rosshoek.com</A>

Some are born great, some achieve greatness,
and some have greatness thrust upon them.

[orvacian]

If you directly connect two batteries in parallel, they need to be EXACTLY the same. This means age, size, capacity and so on. If not they will discharge each other while they sit. A dual battery isolator will work but there is some voltage drop through it. The best thing is a big high current relay switched with the ignition but they can be a little pricey. What you actually want is a bigger alternator more then a second battery though. With constant draw items like lights or fans you are just prolonging the time it will take to discharge the battery.

Here's a example: Let's say you have a 70 amp alternator on your Ford Festiva prerunner. You are running 840 watts of KC Highlites and the Festiva uses 30 amps while running. 840 watts = 70amps + another 30 amps for the trophy Festiva equals a 30 amp DISCHARGE while driving. Your Optima is mabye a 30 amp hour capacity battery. This means your battery would die after 1 hour of driving! So you add another battery. You only get 1 extra hour of run time! And that's if both batteries were fully charged to begin with. What will most likely happen is your alternator will die from all the extra load.
The only good thing the extra battery would do is give you more run time with the car off.

On the other hand, if you get a 120 amp alternator you have an extra 20 amps available above what you need (100 amp draw) and you don't need another battery.

[hoeker]

well done!

Some are born great, some achieve greatness,
and some have greatness thrust upon them.

[Eric_M]

orvacian,
say i run a 120 amp alt. can i just hook it up and call it a done job, or are there anything i would need to do to keep it from cookin anything? so in other words, will i run into any consequences by runing the 120 amp alt. with out doing anything besides bolting it in and hookin it up?

thanks

stupid people shouldnt breed!

[Kbach66]

So much for debuting my new Festiva prerunner at the next MDR race!! Nobody keeps secrets anymore!!

[orvacian]

The output amperage rating of an alternator is the maximum amperage it can potentially supply. A way to think of it is that the alternator has a certain amount of amperage it can give at a time; the battery and electronics will take what they need from the alternator. The battery stores that amperage and the stuff connected to it takes that it needs. When the engine is running the electronics are actually running off of the alternators output, not the batteries stored amperage. It's a little more complicated then that but you get the idea. Most alternators have a built in regulator so it will not overcharge your battery. I have a 140 amp alt and Optima in my truck and it works beautiful. Some older cars have a external regulator but it does basically the same thing. The amount of amperage the battery will draw when charging is determined by the output voltage of the alternator. What the regulator does is regulate the output voltage of the alternator so it stays somewhere around 13-14 volts. 13.5v is pretty standard.

<P ID="edit"><FONT SIZE=-1>Edited by orvacian on 02/12/03 11:09 PM (server time).</FONT></P>