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CJDave dual battery question

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Everywhere I read, everyone says that you have to use isolators to run 2 batteries. I am slightly confused. All of our diesel tractors run at least 2 batteries...the big dog (Mack 500) runs 4. On each and every one, the batteries are just wired together...no isolator...no seperation. When we put a snowplow on my dad's pickup a few years ago, we just slapped a 2nd battery in and hooked them up together as well. What's the deal? Why don't these vehicles keep killing batteries?

Measure once, cut twice...or is that the other way around?
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I hope CJ dave doesn't mind me butting in on his question....
Sorry CJ Dave, just trying to get Farm Jeep a quick answer....

You CAN wire together two LIKE batteries.
IE; If all are new and of the same size and kind. Or if all are used the same age and of the same size and kind.

You CAN NOT wire together a starting battery, and say, a Deep Cycle battery, or a gel cell with out an isolator.
You CAN NOT wire together a old battery or different size starting batteries with out an isolator.
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Reason:
If you wire together a larger and smaller, unlike sizes, or different types, or different ages, one battery will demand more, higher and longer charging from the alternator.
The newer battery, or the one that needed less charge is getting fried (overcharged) while the weaker one gets charged.
The alternator just senses demand and throws current blindly. It doesn't have any way of knowing there is a battery getting fried in the process. (Overcharge is the second best way to kill a battery before it's time)
The battery isolator takes the charge, and distributes it to the various drains on a demand basis for each one.

Isolators,
They are expensive, but worth it for something like and RV that has deep cycle batteries for power when the generator isn't running, and starting batteries for the RV engine and generator engine.

Just don't play mix and match in your Jeep and you should be fine with CJ Dave's set-up.
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The beauty of CJ Daves' dual battery system is it uses two starting batteries, and both will be the same size to fit the double battery tray.
You will probably buy them at the same time, and the continuous hold solenoid delivers the same amount of charge to both units.

You are probably not going to run one down so far you damage it with the engine off, so both stay even... Or get even in short order after the engine is started.

I wouldn't be a bad idea to swap the batteries around, or at least the positive cables around once in a while so you don't start off of the same battery all the time.
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Does this clear it up?

So many cats, So few recipes....
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/wwwthreads_images/icons/smile.gif TeamRush has it right Farmjeep. Mixing batteries is difficult sometimes. THE REASON Jeep guys isolate is the same reason that I did on my service rigs.....to keep from running the cranking battery down with electric stuff like winches, hoists, radios...etc. On your tractors, the batteries all have the same job....cranking the engine...period. Interestingly enough, I DID use a duke's mixture of batteries and got away with it. My main truck battery was whatever the 2000 series Intl gasser took, and my double hoist batteries were....ONE DEEP CYCLE MARINE big jumbo size, and one regular truck like I had up front. I had an unusual situation, however because my hoist was 24 Volt...it used the two auxillary batteries in series when I flipped the "ready" switch to begin hoisting. When the switch was back on "normal" they were in parallel and could charge that way if the truck engine was running. If I got in a jam, I would start the truck, and the two normal truck batteries would team up, side by side in parallel as one half of the 24V, and the jumbo marine battery was the other half. Incredibly, the batteries lasted for YEARS! The only thing that gave trouble was the 12/24 series/parallel changeover solenoid. THAT required periodic rebuilding due to the weak charge circuit it had in it. So the Jeep guys who use my posted setup are just trying to keep from walking home if they use too much auxillary power off the second battery. The open solenoid keeps the cranking battery fresh and ready to go when you are. /wwwthreads_images/icons/wink.gif/wwwthreads_images/icons/cool.gif I'm not trying to sound like a tough guy, but those store-bought isolators are for high school kids, and old folks in their RV. They sell them because not everyone has balls enough to plug in a Hobbs oil pressure switch to the engine oil gallery, so an isolator is an easy-to-install substitute. THE PROBLEM is that sooner or later it is going to take a dump and then you're screwed. That's why real Jeepers would do like the recent post and photos with the dual Optimas and the continuous-hold ,oil pressure-activated solenoid. Now that there's a MAN's setup!/wwwthreads_images/icons/crazy.gif

CJDave
I never believe any statistics unless my moonguys /wwwthreads_images/icons/crazy.gif/wwwthreads_images/icons/wink.gif made 'em up themselves.
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I figured that there had to be a good reason. When I get used to driving a jeep that actually accelerates, I'll probably dive into that dual battery setup. It's a stepping stone to both the winch and the welder...

Measure once, cut twice...or is that the other way around?
Reading CJ Dave's post, I just realized something,
I wasn't using the same terminology that you two were...

To me a battery isolator is a charge regulating device that services several drains from one source (an alternator) and regulates the outputs to each device just like the voltage regulator in an alternator does to a single battery.
Nifty gadget, but expensive.

CJ Dave is talking about manually ISOLATING the battery with a continuously on solenoid to keep it from discharging when the primary battery does.

I guess I should have said Charging Isolator....

The reason CJ Dave could get away with different types of batteries is because there were a lot of batteries, and they were all LARGE...
Large batteries have the ability to work somewhat like capacitors, and save them selves.
He still didn't get maximum service life out of the batteries, because of the over charging, and the mix and matching...
It's always better to have a balanced system...

Sorry about the confusion folks.

I'm desperately trying to figure out why kamikaze pilots wore helmets...
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Tell me if this is stupid or not. I wanted to set up two completely batteries that were not connected. I wanted one to run the Jeep as normal and the other that would run all the extras I add, like lights, pa system, winch. Anything else I can think of to add on. Is this possible? I was thinking if I had a separate fuse box I could do this. Am I way off?
Thanks, Jeff

'83 CJ7 258 i6 31x10.5 3in. lift? /wwwthreads_images/icons/cool.gif
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Jeff
If you have enough alternator to run your lights (etc) then you really don't need a dual battery set up like you describe. The main reason for dual batteries is if you are going to be running a high load accessory (like a winch) for relatively short periods. It would not be reasonable to upgrade the alternator to be able to meet the demands of the winch as it is not used full time. Running dual batteries gives you a much larger "reserve" upon which to draw. This allows for longer winch use and/or longer battery life compared to a single battery. If you are planning for more continuous use items like lights, stereo, etc. you are much better off to match alternator output to your requirements.

"My other car is a BULLDOZER"
/wwwthreads_images/icons/smile.gif The answer is "Yes" and "No".....Dozer Tom rubbed one of his tracks up against the answer in his reply, but did not completely speak to the exact question. The reasoning for having a second battery as Utahjeeper pointed out is usually to have a bigger "reserve". The other reason is to isolate certain high-draw loads so that you or your less-experienced riders cannot drain the cranking battery sitting under a shady tree listening to the radio and running a huge amplifier with the engine not running. Circling back to my ORIGINAL dual-battery scheme, you satisfy both requirements by using an oil-pressure activated solenoid to connect the batteries. No oil pressure....no connection. THEN you feed a big fuse panel (JC Whitney has Cole-Hersee brand....VERY good!)from the second battery , and the kids sit there wasting the current like crazy, but the cranking battery doesn't even know it.......the solenoid is open. You start the Jeep...the oil pressure-activated switch feeds the solenoid current and it closes so the alternator can charge the second battery. You can even have a button on the dash to "jump start" yourself in case you went off and left the key on or the brake light switch stuck on./wwwthreads_images/icons/wink.gifAs Tom mentioned, it is reasonable to want to upgrade the alternator as well, since in the end, where does all that current have to come from?/wwwthreads_images/icons/crazy.gif

CJDave
I never believe any statistics unless my moonguys /wwwthreads_images/icons/crazy.gif/wwwthreads_images/icons/wink.gif made 'em up themselves.
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there are multiple ways to run a dual or in the setup i plan triple batteries. i prefer to use very large solenoids. i am working on a diagram to do more than a basic isolation, as i want to seperate or link batteries at will. this does require more parts and wiring, but there are several advantages such as cold weather starting, extended winching, underhood welders,high powered communication equipment, and the list goes on and on. i will try to get my drawings posted or available once they are finished.

dan

/wwwthreads_images/icons/smile.giflet it snow/wwwthreads_images/icons/smile.gif
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/wwwthreads_images/icons/smile.gif I can visualize this setup, Dan.... a common (-) bus bar....a common (+) bus bar...each battery has a continuous solenoid on the (+) cable to the bus bar.....the solenoids are switched separately....control power is connected to every (+) battery side, but uses a diode in each feeder to prevent backfeeding and trying to act as a charging circuit.....yes, I can visualize that....a row of batteries in the back.....moonguys/wwwthreads_images/icons/wink.gif/wwwthreads_images/icons/smile.gif checking the electrolyte levels and cleaning up the cases./wwwthreads_images/icons/crazy.gif

CJDave
I never believe any statistics unless my moonguys /wwwthreads_images/icons/crazy.gif/wwwthreads_images/icons/wink.gif made 'em up themselves.
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you are very much on the right track dave, and i should have emailable copies of my diagram soon. i am still debating on the drawing format as i have it in true electrical diagram format (ie symbols and lines). rather than changing to cartoon style maybe i will just put a legend on the bottom. i will email you a copy tomorrow to see if you can make heads or tails of it.

i finally found a moonguy for the truck, but i had to drive 4.5 hours for it. actually i was at a convention this weekend and found a wally world that had two cases of them./wwwthreads_images/icons/cool.gif

dan
NECESSITY IS THE MOTHER OF INVENTION
/wwwthreads_images/icons/cool.gifLET IT SNOW/wwwthreads_images/icons/cool.gif
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Hey Blackjack, I would love to see that diagram as well. I interested in learning more about this.
Thanks

'83 CJ7 258 i6 31x10.5 3in. lift? /wwwthreads_images/icons/cool.gif
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