Dual battery set-up

What's the best way to run a dual battery set-up. I'm definitely no electritian so "dummy terms" are appreciated. Will I need to run a larger alt.?If so which one is a good swap?

 

A battery isolator is needed. Otherwise the battery will not charge properly.

http://www.e-marine-inc.com/products/alternators/isolators.html

 

No need for changing the alt. Just make sure your secondary battery is used to run your optional equipt. If the Isolation diode going to secondary battery burns open, you wont know it except by loosing your optional equipt. You can install second volt meter to monitor charge of second battery. Your battery isolator will come with simple inst.

 

In case you're not familiar with what these guys are referring to....Here is the rundown.
So you hook up two batteries to run your extra goodies...winch, lights, disco ball, etc....That's a good move in my book...BUT...hooking up two batteries to run your extras is not for more power (sorry if you already know this) The second battery is so that the other battery (the one that starts and runs your Jeep) remains full of charge, so you can go home when your done.
Here's an example....Lets just say for argument sake that you have one battery and your engine is off...
You decide to run something that takes a lot of juice (again, your engine is not running), you turn on your lights and run your winch until the battery goes dead...Which would be fast. Well...since you only have 1 battery...and that one battery is how you start your Jeep...you're pretty much had...unless you can get a jump start, or you're on a hill to roll start it.
Well...now you go with two batteries...If you hook the two batteries together so that the alt charges BOTH batteries...then both batteries will act just like the single battery did when you made it go dead by running your stuff...because current is being drawn from both batteries.
Okay...So what to do? You can unhook one battery from the other... and hook all your accessories to the unhooked battery, that way the one that starts your Jeep will not go dead. Well...this is better...because you can still start your Jeep even though the second battery is dead...But...now you have to charge your second battery so you can use it again. You could hook it up to the other battery and then unhook it again when you are using it....but that's a massive pain....The answer to that is the battery isolator mentioned above. What this does is that is it makes both of your batteries separate power sources...just like running the battery with it hooked only to your accessories...except with the isolator...it gets a charge from your alt...it will get power (charge) from your alt, but will not drain the other battery (your starter battery). So you can run your second battery dead as a doornail...get in your Jeep, fire it up and it will charge it right up...The idea being...the battery that starts and runs your jeep stays charged and full (so you can go home) while you punish your other battery with all of your accessories. There are other advantages to this...but this is the main outline of it. Again...I apologize if you knew all this.

 

Thanks, that helps. All info is appreciated. I think I understand how it all works now.

 

This is a top notch way of doing it. Great job.

 

I've got the same perko switch in the '99 - perkos are great. Marine quality, a little pricey, available at Boat us, west marine, etc.

 

I would never use the diode / electronic isolator. I've seen way too many fail and they either won't charge the second battery fully (diodes drop 0.7 volts), or they cause the alternator to charge at a higher voltage putting more stress on the alternator. There are a few companies now that sell constant duty cycle relays specifically for charging dual batts. They're simple, reliable, and the second battery sees full alternator voltage. These look like a starter relay, but instead of passing a very high current for a minute or so at a time, they are designed to run 80 to 100 amps continuously.