How to run dual batteries?

[ninjapumkin]

So my dilemna (friend had to bring it up) I have lots of accesories now.
He says to much for single wire alternator and one battery. Battery is in the trunk.
Running to battery for access. i have:
MSD6AL
Electric fan
Electric water pump
Electric fuel pump
Line lok

How can I run dual batteries. He said something about an isolator.
With this i'm stumped.

 

[RustyRatRod]

See if this will confuse you more. lol

http://ezinearticles.com/?Battery-Isolators-Explained---A-Must-Have-For-Powerful-Systems&id=683228

 

[RustyRatRod]

Here's a simplified, but accurate diagram for you, too.

 

[67 coronet]

isolator is a part that you need to run dual batterys correctly for an rv system.normaly you just buy a kit with wiring and such.take a look at summit racing part #
prf-40102 to see what it looks like.

 

[440roadrunner]

1---I think running dual batteries in a car is silly. You still need enough alternator to charge them, so if the alternator cannot keep up, you need more alternator NOT more battery

The exception to this is if you are one of the irritating people who shows up in a park/ beach, opens the doors, and turns the stereo up with the engine off

2--PLEASE do NOT run a 3 terminal solid state "isolator." These have failed in a number of marine installations, and in THREE cases I know of specifically, were the cause of a bilge explosion. Here is how they can fail in a dangerous mode. Isolators are nothing more that two large diodes. The MAIN battery diode is usually under the most strain and can fail OPEN With a conventional "sensing" regulator, this means that the MAIN is NOT getting charged, and the regulator says "hey, the battery is going low, let's charge!!!!" So the regulator ramps up the charge voltage, and the regulator/ main battery sees none of this because it is now disconnected from the alternator output!!!

But the alternator is charging the LIVING HELL out of the auxiliary battery!!! The voltage is going HIGH, the battery is bulging at the seams, and things are NOT good!! What I'm referring to is one like this, again do NOT use these

If you want to use an isolator, buy what is known as a "continuous duty solenoid" These look vaguely like a Ferd starter solenoid, except they are designed to be powered, well, "continuously." AND these are what Rusty is referring to in his diagram above.

Just hook the two hot leads of the two batteries to the big studs, wire one of the small terminals to ground, and wire the remaining small terminal to switched ignition

 

[tpodwdog]

1---I think running dual batteries in a car is silly. You still need enough alternator to charge them, so if the alternator cannot keep up, you need more alternator NOT more battery

The exception to this is if you are one of the irritating people who shows up in a park/ beach, opens the doors, and turns the stereo up with the engine off

2--PLEASE do NOT run a 3 terminal solid state "isolator." These have failed in a number of marine installations, and in THREE cases I know of specifically, were the cause of a bilge explosion. Here is how they can fail in a dangerous mode. Isolators are nothing more that two large diodes. The MAIN battery diode is usually under the most strain and can fail OPEN With a conventional "sensing" regulator, this means that the MAIN is NOT getting charged, and the regulator says "hey, the battery is going low, let's charge!!!!" So the regulator ramps up the charge voltage, and the regulator/ main battery sees none of this because it is now disconnected from the alternator output!!!

But the alternator is charging the LIVING HELL out of the auxiliary battery!!! The voltage is going HIGH, the battery is bulging at the seams, and things are NOT good!! What I'm referring to is one like this, again do NOT use these

If you want to use an isolator, buy what is known as a "continuous duty solenoid" These look vaguely like a Ferd starter solenoid, except they are designed to be powered, well, "continuously." AND these are what Rusty is referring to in his diagram above.

Just hook the two hot leads of the two batteries to the big studs, wire one of the small terminals to ground, and wire the remaining small terminal to switched ignition

smart man !

 

[440roadrunner]

For the record, solenoids are what 67 Coronet and Rusty were talking about, and not those solid state ones.

I should have mentioned it depends on why you think you need more battery. If you need more cranking power, as a 1000HP monster, you don't want ANY isolators/ solenoids. Just mount both batteries in the trunk and hook them together with the largest cables you can get. Many over-the-road highway trucks use parallel 12V or series 6V more more power. Some of them used to use a special 24v start/ 12v run lashup, but these were troublesome, and required a special, complicated, expensive solenoid known as a "series parallel" solenoid I think most guys got away from them

As you can see, complicated, messy, and a lot of connections to fail

http://www.texasindustrialelectric.com/T_114_12_series_parallel_switch.asp

 

[benno440]

you dont need dual batteries, i ahve all of that you run plus many more power upgrades like a dual amps and subs power windows etc etc.

i ahve a single optima 880cca battery and runs with no problems also a powermaster single wire alternator.

 

[ninjapumkin]

Thanks for all the input guys. Once again lots of food for thought.
So the deno 60amp alternator should be good. Worse comes to worse all wiring that requires direct power from battery is heading to trunk anyways. So if I run into a problem I can always add an extra battery and tray back there.