Dual Batterys ? One primary One Aux ?

[Mrnicks]

Alright this is what I have; 99" ranger 4.0L 4X4 xlt. extended cab,
two batteries
one 4yr. old red top optima
one brand new stock diehard.

The optima is starting to show its age. During this winter after sitting for 4-5 days under 32.F it is too low to start the truck. I'll trickle charge until fully charged drive the truck for days and it's fine. Just when it sits in the cold for too long. And I use to be able to play my radio for hours with the truck off and now I can only get about 45min before I have to start it.

What I want to do is be able to connect one of the batteries all the time and connect the other just when i need it. Like when the truck is off and I need to run accessories like my compressor, radio, or invertor. Or to even jump myself if needed. I have a pretty good idea how to do this since I am a electrician. I was just wondering if anyone else has already done this and the route they took. Now, I know I'm not going to be able to have the aux battery in the charging system do to the alternator and them having different specs. So I can handle having to permanently wiring to float charger to charge the aux battery. What do you guys think.

I really wish I could just buy a bigger alt. and two new optimas. Do you think I would kill the new optima by adding it to the old one and running them all the time like how a diesel has two? I've seen this happen on large battery backup systems. I;m not sure how it would be in a vehicle.

 

[Roadkill]

Basically what you want is the setup we have on our rigs. Only difference is we carry 4 batteries. Starting takes 3, and 1 is for cab 'extra' electronics. All we do is install an isolator on the one battery and run dedicated power lines into the cab. The battery that is 'out of the loop' for starting is charged any time the rig is running and can be easily switched back into the grid for main power if needed.

Pretty simple setup, just need a place to add the second battery and to bolt the isolator.

 

[COPPERHEAD85]

AGM and flooded batteries do not play well together.you need a pair of one or the other.
i use an isolator with 2 AGM's in the bed.alt. charges both but they are separate on the load side.one for the engine the other for lights and winch.
some people don't care much for running an isolator because its something else to fail.Ive ran the one i have for 5 yrs now with zero problems,it was about $70 plus wire.
you can goggle battery isolator and get a ton of info instead of reading my crummy typing...lol.
its the blue box above the red coil ........

 

[Mrnicks]

So it seems that the "isolator" is a high amperage diode. It allows current to be pushed into the battery but not back into the rest of the system. So I should be able to use that to charge the battery when needed and add a bypass when I want to add some extra juice to the system. Only when the truck is off of course, or to jump the other battery.

 

[Roadkill]

That is pretty much it. Isolators will ensure your primary battery gets charged first then the aux battery gets charged.

Like I said we run them on our rigs and our trucks run pretty easily 25000 miles or more a month.

 

[Mrnicks]

Cool, thanks. I found some decent schamatics online. One more question, do you guys all have matching batteries or are some mix and matched?

 

[Roadkill]

It will depend on the isolator you use. A good one will allow you to mix batteries. Similar to how boats use a starting battery and deep cycles all on an isolator unit.

 

[COPPERHEAD85]

AGM= 13.7 volts
FLOODED=12.6 volts

believe me it makes a difference.most AGM deep cycle come backs to my store are due to under charging.takes me about 3 days to get them back.
the reason is they are using a charger made for flooded.

 

[Mrnicks]

Ah, I see what your saying. So, just by using the isolator to "islolate" the other battery circuit it should be fine. The two different bateries won't fight each other? I have a factory altanator, will the isolator help save that device at all. Or will it just lessen the life because of the higher load like normal? Obviously, I'm trying to do this on a tight budget.