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Discussion Starter #1
Here's a few questions I have had about adding batteries to a truck

1. If you were to add an extra battery to your electrical system will this increase the load put on your alternator?

2. If you had two of the exact same battery can they be directly wired together in parrallel to retain the correct voltage, but double the amperage output potential?

3. If the addition of more batteries does not cause significant increase of load to the alternator, and all your batteries were the same model and spec, could you incorporate 3 or 4 batteries, all wired directly together in parrallel, tripling or quadrupling the potential output of amperage while keeping the correct voltage?

4. What kind of switches are available that will allow the connection of two batteries that will charge off a common source, the alternator, but will not share a common load. Like one smaller battery for just the starter and computer, and a larger battery for everything else, like lights and maybe a winch.

These are just a few things I have wondered about but am not neccessarily going to do. If you got the time and knowledge educate me! :D
 

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Discussion Starter #3
ATLRoach said:
Jon I think this was dicussed on the old board. Might wanna do a search?
Hey, don't be that guy! ;)
 

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Puckett said:
1. If you were to add an extra battery to your electrical system will this increase the load put on your alternator?
Not if you use a battery isolator.

2. If you had two of the exact same battery can they be directly wired together in parrallel to retain the correct voltage, but double the amperage output potential?
That is possible but how much current do you need?

If the addition of more batteries does not cause significant increase of load to the alternator, and all your batteries were the same model and spec, could you incorporate 3 or 4 batteries, all wired directly together in parrallel, tripling or quadrupling the potential output of amperage while keeping the correct voltage?
Voltage in a parallel circuit is constant. Yes, if you bused the batteries together you could maintain the 12 volts and increase the current. Do you realize how much current you're looking at with 4 batteries?

4. What kind of switches are available that will allow the connection of two batteries that will charge off a common source, the alternator, but will not share a common load. Like one smaller battery for just the starter and computer, and a larger battery for everything else, like lights and maybe a winch.
A battery isolator.
 

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Discussion Starter #5
akshunj said:
Not if you use a battery isolator.

That is possible but how much current do you need?

Voltage in a parallel circuit is constant. Yes, if you bused the batteries together you could maintain the 12 volts and increase the current. Do you realize how much current you're looking at with 4 batteries?

A battery isolator.

These are all just question I have. As of right now I'm not going to be changing my electrical system. I just wanted to know for if I do change it, and I'm sure it will come up in a search on the new board now in case anyone else wants to know!

If you don't use a battery isolator, and have two of the same batteries in parrallel I assume the load on the alt. would be twice as much as a standard battery for charging purposes. In the event you would be winching, would this decrease the load the alt. would see during winch operation since there is more stored energy in the two batteries?

Could an analogy be like a water tank with a pump to fill it? If you have 10 gallons and you could use 10 gallons then the pump will fill it up. If you added another 10 gallons to the tank, you could drain 20 gallons at a time, but the pump would be on twice as long as before to fill it back up.

With having two batteries non isolated, the alternator may work half as often, but will need to create twice as much energy to re-charge them right?
 

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When you run a dual battery setup you should run two brand new batteries, same brand, nearly the same mfg date. Same reason that alkaline batteries say not to only change on battery in a system but to always change them all.

The alternator will not work twice as hard to charge the batteries. In fact, it's -impossible- for the alternator to work any "harder" than it normally would. It either supplies enough charge to charge the battery, or it doesn't. An alternator is 100% duty cycle. It's output is directly proportional to the RPM of the motor. The higher the RPM, the higher the voltage peaks are coming out of it and the more charge that gets to the battery.

Assuming the load on your electrical system does not change between your single battery and dual battery setup then the amount of current needed to keep the dual battery setup charged will remain the same.
 

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Like Bob said the alternator won't work any harder. The alternator provides it's rated amount of current. You can place a load large enough on it to cause a drop in voltage, for example with a winch and you'll see the lights dim as a result.

What the battery isolator does is prevent one battery from discharging the other. For example, if one battery was fully charged and the other 1/2 charged then the depleted battery would drain the full one until their charges equalized. This is not good if you plan to start your truck off the other battery.

With the isolator, you can winch or listen to music all day off one battery without having to worry about killing the other one. When you discharge one battery your alternator is only meeting the current requirements of the one discharged battery and not two of them.

Another option with an isolator is you can use a normal battery for everyday starting and accessories, but use a deep cycle to hook your winch and or big amplifiers to. That is probably the best way to go.
 
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