XJNick, question

[Snitty]

I just got a free battery, same thing i'm running now... i want to run dual... how about some isolator coaching here... where to buy, what kind, how to run it? is it safe to use a relay, or does the sudden jump hurt the batteries?

i would have PMed, but i figure if i'm going to learn, we might as well all learn

 

[XJNick]

Hi,

First off let me say that I haven't used any isolators or switches on my Jeeps, as I don't have any dual battery setups. So I have no experience as far as what would be the best brand or where to buy one.

I guess what you need to do first is decide how you want to do this.

One approach is to continue to run the vehicle starter and accessories as normal off your current battery, then add an isolator/combiner unit and a second battery, to provide a "backup" power source. This would mean that normally the second battery would be charged from the alternator, but through the isolator, and would have no load(s) on it. But flipping a switch would cause the isolator to combine the second battery into the main power system (in paralell) to provide more amperage capacity to the system when you need it. See figure One here: http://www.hellroaring.com/4wheel.htm for a simple schematic and a company which manufactures combiners/isolators.

Another way you could do it is to have your current battery remain hooked up to the starter and engine control systems in the Jeep, while a second battery is hooked up to all the accessories in the Jeep. Then you'd hook both these batteries through an isolator to the alternator, so they'd both be charged, but yet they would be powering separate systems.

Of course there are other ways of doing it as well, but the safest ways are those which use an isolator of some sort (even if it is just big diodes), to prevent having to have both batteries always connected in paralell. Also note that you NEVER want to connect the batteries in series, or your Jeep would receive 24 volts, which I guarantee it would not like :mrgreen:

Lastly, keep in mind that on any dual battery setup, you've now got two batteries which the alternator must keep charged. Figure that the alternator output to each battery will be roughly half of its total output if the batteries are at the same state of charge, so don't expect it to be as effective as it once was. I'd be tempted to check the battery voltages from time to time and make sure they are remaining charged (should be at least 12 volts -- a 12 volt battery is fully charged at about 13.4 volts). If neccessary, put them on a 12volt charger from time to time.

Hope that helps :mrgreen:
-Nick :!:

 

[ROGLSTUBB]

The way I have seen dual battery setups is to use a ford type soleniod mounted on the firewall to connect the batteries in parellel. You can either switch manually with a toggle switch or have it connected to your ignition switch to where when you switch the ign on you will connect your "reserve battery". The ign switch is best that way everytime you run your Jeep you charge the battery and dont have to remember to flip on or off the switch. I have used ford solenoids to run in constant on situtations ie"inverter, amps" and have had good results.

 

[Special_K]

I've got a dual set-up and in my opinion, you're much better off going with an isolator system. Given the risk, you may be better off making the plunge and getting a dual battery connector kit. I've seen them made by "Wrangler" and by "Painless Wiring". Both brands are good...I have the system made by Wrangler. The wrangler system also comes with a nifty light to let you know what position the solenoid is in (green = single battery operation, dual battery charge; red = dual battery operation; off = single/primary battery operation and charge, secondary battery isolated).

The system under the hood (with the solenoid):

The one problem I've experienced that I intend to correct is that occasionally the switch is kicked to off and I don't notice it until the secondary battery begins to drain. My auxiliary lights, amp, AND SOLENOID, etc. are powered off the secondary battery. When this happens, I have to manually jump the batteries to even activiate the solenoid to allow the secondary battery to receive a charge (by putting it on the green setting). I'd have the same problem if the solenoid was powered off the main and I drained the main (say, by leaving the headlights on)...then I'd have to "jump" the the solenoid to allow me to switch the power over to secondary. A solution is to connect the solenoid power to both batteries, but I want to be sure I'm not compromising seperation and circuitry by allowing the system to drain both batteries through the solenoid connection. Anyway...it's a small problem and it's fixable, I just haven't put much thought into it. The last accidental isolation/drainage incident caused me to damage my speakers so it's taken on a greater sense of urgency.

Painless costs about $100-$200 and Wrangler costs about $100 for battery isolator and wiring kit. You can do it cheaper with your own parts. Depending on how you connect the solenoid and how you want to use the batteries, there are a few different ways to wire correctly...just be sure you know what you're doing if you do it with your own parts.

 

[XJNick]

The way I have seen dual battery setups is to use a ford type soleniod mounted on the firewall to connect the batteries in parellel. You can either switch manually with a toggle switch or have it connected to your ignition switch to where when you switch the ign on you will connect your "reserve battery".

The isolators/combiners basically ARE large solinoids for switching the batteries in/out of the system. They do provide one major function which a regular solinoid doesn't; they have large diode(s) which allow power to flow INTO (but NOT out of) the second battery when not switched in "dual mode", so as the second battery is ALWAYS remaining charged from the alternator.

Plus, I'd be a tad nervous having the batteries always connected in paralell when the vehicle is running without the use of a diode-protected isolator...

-Nick :!:

 

[ROGLSTUBB]

I understand the use of the diode for charging the battery when using a switch type setup. This would allow the alternator to charge the battery when running yet not allow any current draw from the battery unless switched to on. My question is what makes you nervous about having two batteries hooked up constantly with the key in the on postition. Both batteries still only have 12.6 volts. so there is no over voltage situation. The only bad thing I could see if there was a unfused short it could burn really fast because of the amperage potential of both batteries. Or is this what makes you nervous. I am not understanding your concern. I am planning on using a battery back up on an keyless entry/alarm/remote start combo I will be installing in a few weeks. I would really like to understand your uneasyness of this setup. Thanks

 

[XJNick]

Hi,

I guess I phrased my last response wrong, as I was trying to say that I'd be careful when using two batteries always connected in paralell mainly because the increased amperage capacity means more trouble if you run into a short condition, but also because if you manage to drain both batteries, you'd no longer have a way to start the Jeep, as you would if you use an isolator and keep one battery for the Starter and engine control system only.

This is just my opinion, though. I asked a friend of mine today (who's also knowledgeable about battery and charging systems -- more so than I am) what he though about this, and he believes that

"It is ok to put both batteries in parallel. They should ideally be matched in capacity and brand. Wire both of them to a single terminal point and run ALL the load from that point. Try to keep the wire length from the terminal point to each battery the same."

Hope that helps :mrgreen:
-Nick :!:

 

[ROGLSTUBB]

Thanks for the clarification XJNICK. I kinda thought that was your concern but I wasnt for sure. I do like the idea of using a diode for a switch type setup. I have never heard of that one before.

 

[randomjeeper]

hey i just kinda glanced over the question you had, and i remember seeing pictures of 3 different types of dual battery set ups either in jp or some other 4wd magazine (i only looked at 2, the other one started with a 4...). thought i'd mention it.

 

[Snitty]

still not too sure on what i'll do.. but thank you very much with the help