Quick dual battery setup question
 

I am finally going to install the second yellow top optima I have had for awhile.
Both batteries are the same. I am planning on using a race car kill switch in between them so I can separate them.
http://www.turnermotorsport.com/imag...ng_01335_1.jpg

I don't need an isolator for any reason right?
Plan is to have the battery available but only connected maybe 50-60% of the time since I dont have a big stereo, or anything right now that draws a lot of power. Pug in incase of jump start needed, camping and need some more power when engine is off, recharging the second battery, etc.

thanks

Isolator not needed. I just run a 200 amp. solenoid (i.e. big relay) between my two batteries:
- http://www.4crawler.com/4x4/CheapTri...l#Installation

Solenoid is on the top/center of the image below:
http://www.4crawler.com/4x4/CheapTri...x/p1020376.jpg

Simple switch on the dash to select between automatic operation (batteries in parallel when ignition is turned on) or manual operation.

well I would suggest getting a isolator and running the relay off of a switch.

For the reason that it will be charging both batteries all the time, which will kill your alt. Also if you run on just a switch its not evenly charging both batteries.... Which in return... kills the alt. The Isolator evenly charges both batteries and also has an auto relay switch on it so you can turn off one whole battery if you wanted.

I got one from my dual batts and it made a huge difference in the charging. I have my fogs and everything running on one batt and the subs on the other. And I get no light dimming or anything. But I also have mine wired into my radio so when it comes on. It starts charging the rear batt immediately.


I would suggest investing in a 200amp isolator just to protect your yellow tops and your alt. But do the Big 3/0 mod when installing the dual batts also. This will greatly improve the charging system of your rig.

Just my thoughts and suggestions.... But if you have any more questions just PM me and ill answer anything you need to know


But of course. 4crawler is correct. I like isolators but a 200amp relay would work fine also haha. Your choice:)

can you explain manual operation?

also will my idea work, basically the kill switch is like the relay, but without the remote on/off switch? do you see any negatives besides having to turn the kill switch key when I want to disconnect the batteries? I am looking for the simplest solution.

and what is the Big 3/0 mod?
I am using 2/0 wire, if that was a wiring size reference.

Simple: On and Off. Explained in detail on the web page link above.

Yes, as long as you remember to switch them on and off. Without an isolator, you need to remember to disconnect the batteries when the engine is not running to keep them from draining each other.

Also, think about the wiring for the switch and where it'll be located. Running heavy battery cables is a lot different than running normal sized wires.

sorry my work blocks your site for some reason, so I cant see the link.
https://www.yotatech.com/forums/f2/d...talled-198973/

I had thought isolators were more expensive than this but I might just go ahead and get it instead. then I wouldn't need the kill switch.

So the isolator works by knowing if the alternator is outputting current, and if not, then it disconnects the two batteries from each other right?
I assume it also reduces alternator load by switching back and forth between batteries when the vehicle is running too? How does it know when to switch?

The solenoid control logic, from Painless Wiring, allows for 3 modes of operation:

1. Mode one is used for most conditions. In this position the system has twice the normal starting amperage automatically. Batteries are isolated with the ignition off, thus preventing the "dueling battery syndrome". When the ignition is on (and the engine running) both batteries are charged (in parallel) from the alternator.
2. Mode Two is provided to lock out the auxiliary battery. In this mode the secondary battery can be held in reserve when heavy winching or extended cranking are expected. Or, in my case, I have the winch connected to the auxiliary battery, so this way the winch will not drain my main battery. In this mode, the main battery is charged by the alternator, but not the auxiliary one.
3. Mode Three is used if the main battery won't start the vehicle. This mode allows a self jump-start from the auxiliary. Both batteries are charged by the alternator in this mode, however, the solenoid remains energized even if the engine is off.

So the Sure Power isolator I posted does those three things?

Yes. correct. I knew there was another reason why the isolator was needed. Thanks 4crawler for reminding me. Yea the batteries will drain each other. Also the isolator works so that when its off it separates both batteries so they are not discharging each other. Also when it is on it regulates the power draw between the batteries so it is a balanced charge.

Not familiar with the Sure Power products, might want to contact them and ask that question.

Usually isolators are just passive devices. They have diodes or some other solid sate device inside that lets charging current flow into each battery but blocks the two batteries from "seeing" each other, thus the term "isolator". The isolator isolates the two batteries from each other. Classic application is an RV; main battery for engine starting, aux. battery for all the other loads in the RV, aside from charging when the engine is running, the two batteries are completely independent (isolated).

Some fancier isolators have switching internally to connect the two batteries in parallel when needed.

I like the simplicity of the solenoid setup, have had mine installed and running without problems for about 12 years now.

And an isolator typically does not do any switching of charging between the batteries, nor do multiple batteries increase the load on the alternator, at least in terms of making an alternator put out more current than it is capable of. The alternator output is controlled by the voltage regulator. It'll put out what it can into 1, 2 or 100 batteries. I run a 160A PPW alternator on my truck and it makes a faint, high pitched whistling sound when it is putting out a lot of current. On the times I have drained one battery and used the manual mode to start the engine, I can hear that alternator working hard for about 20-30 minutes as it is charging the one dead battery (plus the one fully charged battery).

ok Ill get that Sure Power one then and not use any kill switch in the lines.
Planning on putting the secondary batt. in a marine box in the back seat area with a quick disconnect external to the box. But I might decide to just put it under the hood like everyone else.

Thanks guys.

Roger, so the one you posted is not the functions that Sure Power will deliver probably. So I would then have to hook up my accessories to the secondary which I dont want to do. I want to have something that will give full parallel power when I want it to.

Can you please explain the solenoid briefly since I cant see your site. Ill check out the full thing tonight at home.

No problem.

Remember one thing though. When wiring the battery in place. Run with nothing less then 4 gauge wire. If you have enough do 2-3 strips of it. Or if you can afford it I would run 1/0-3/0 for the battery. I have a run of 1/0 for my battery and it works perfectly fine. Anything less the 4 will not be a sufficient charge and will have to much resistance.

Also make sure all your grounds are not smaller then 4gauge either. My expereience has taught me to never run my grounds smaller then your power wire.

Alot of people run the dual batts under the hood and then just run all 1/0 gauge for all the connections(Me being one of these people) haha.

Good Luck with the install. Post pics haha.

P.S. Ok, I am running the PAC 200amp Isolator. But this isolator features 2 large terminals and 2 small. the big ones are for each battery of course, the smaller two are for ground and for the built in relay switch.

So when installing you connect a line off your main batt and connect to the left terminal. Run another line from the right one to the aux batt. then run the ground and run a line to be used with a 12v on when you want it to. You can run a switch inside or run it through the radio or which ever.... It just need 12V to kick on so it will start to charge the dual batt.

If you turn the isolator off it stops charging to the aux batt and puts full charge on the main battery. I think it also has the type of modes that 4crawler is talking about. Mine definitely performs for what I use it for. I used to run my system off both batts and I could drain them both in a matter of seconds. Now I get no draining what so ever!! So I would suggest in the investment.

Heres a link: http://www.amazon.com/PAC-PAC200-Bat.../dp/B000CEBXRS

I am still a bit confused as to what kind of isolation unit I need. I'd like to know what roger's does and if the Sure Power does supply parallel power when needed.

Correct, I was explaining the operation of the system I have.

Solenoid (a.k.a. big honking relay) connects between the two batteries.

It turns on and off in the 3 modes posted earlier. When the solenoid is on you have two batteries in parallel. When the solenoid is off, you have two separate batteries.

Yep. Same thing I said only 4crawler summed it up and made it a little easier to read haha. Thanks.


The solenoid works exactly like a switch. You switch on power to both batts and switch power off.

Ok I understand now. Please bear with me as I am an ME....

anyways, your solenoid could also be connected to your ignition wire so technically it is synonymous with my kill switch idea, only it does it automatically where I would have to pull the key when I shut down the truck and put the key in to restart if needed...?

I think I am back to the kill switch Idea now since Roger basically has the same thing, but with a dash switch instead of a physical key.

Or I guess I could do the isolator and a Kill switch so that the second batt would remain charged independent of the first, but then I would wire it so that inserting the kill switch key brought the two batts in parallel for full power. thoughts?

Ok. Not really. If you use a solenoid it will kill the power the same way. but when you turn it on it has no regulation when charging.

I suggest a isolator. They dont cost much but they regulate the power draw from the alt a little better. Im just trying to save you an alternator down the road.

Your call though haha. Im just a guy on the forum.

Yes, in Mode 1 the solenoid turns on and off with the ignition. So if you were diligent and turned your kill switch on and off with the ignition this would be the same. Or in modes 2 and 3 (off and on), this is identical to your kill switch. So with the solenoid, you have both full manual control like a manual switch (turn the solenoid on and off with the switch) or you can have the fully automatic mode where the solenoid turns on and off automatically.

A solenoid setup is pretty simple, think of a switch and relay for something like fog lights. Same thing, only the relay is a bit bigger.