[Guest]

I remember CJDave touched on how he creates his dual battery isolator with a heavy duty, constant service relay wired to an oil pressure switch. Here's the question...If you're cranking the engine (trying to start it) you don't have enough oil pressure to push the switch, right? So you are only on one battery to start the engine... If that battery is dead, how do you get juice to the starter...Can you run a second wire to the solenoid that is switched ( ) power, so you can flip the switch, turn the solenoid on hot, and jump yourself? Would you want to? It seems to me that it would be a lot easier to run my solenoid activation power off of the ignition switch...have it on accessory and you've got one battery. Key off and you've got one battery. Turn the key on, you've got two...winch, start, whatever. What am I not thinking of? This seems easier and cheaper....(which, if I've learned anything in my limited jeeping experience, is usually worse than harder and more expensive /wwwthreads_images/icons/smile.gif).

Measure once, cut twice...or is that the other way around?

 

[291]

Yep farmjeep, you are correct. I mentioned this to CJdave in one of the many replies to his post. He suggested that if you want to use both batteries for cranking (since the oil press sw will be open circuit as you said) have a manual toggle switch running in PARALLEL with the oil press sw that, when fliped on, connects the soleniod to ground enabling both batteries to be joined while cranking. i.e. if either the switch or the oil press switch is a closed circuit, the batteries are acting as one.
Have you built yours yet? I'm working on a tray to hold both batteries right now.

/wwwthreads_images/icons/cool.gif Big Ed
'88 YJ, 4" susp,3" body,33's,283 Chevy V8,TH350,4.11's,D30,D35c

 

[13337]

There are a couple of ways to do the dual battery thing. See the attachment for the way I intend to do mine. It may give you an idea or two....
Or, it may just be a waste of time... I never know...
--------------------------------

Your stock ignition switch is way over taxed the way it is.
Adding something else to it, especially something high drain, may be, 'the straw that broke the camels back', so to speak...

Attached is a rough wiring diagram of the set up I'm going to use.
It uses a remote switch. Mine will be mounted in dash, but some might want to hide the switch, or put it under the hood.

Factory Starter Solenoid,
Self explanatory.

Continuous Hold Solenoid,
Large truck or Heavy equipment supply house, and Maybe NAPA. $13 for mine.
(They may call it a large accessory really.)


Oil Pressure Switch,
Normally open 10 lb. Hobbs switch is what I have planned. About $10 at NAPA.

Self Start Override Switch, any automotive flip switch or normally open push button.
$2 at NAPA.

I use 2/0 (not 2 Ga) fine strand welding cable for all of the heavy battery to starter connections. I use solid copper ends, crimp them down, solder them, and use heat shrink tubing.
I don't have failures.

Hope this helps some, Aaron.

If Chris Columbus "Discovered" America (with 25 million already here), Can I Go "Discover" Florida?

 

[Guest]

I have been doing all the measurements for the cables, trays, and etc. I think I'm going to end up putting one battery in the stock location, and one on the opposite side of the engine bay...Here's another question that happened to come to me then...it seems as though the "primary" battery is the one that will be doing the most starting and cycling...would I want to put a deep cycle in as my primary and have a good starting battery backup...or have 2 deep cycles...or have two starters...or have a starting primary and a deep cycle backup?

 

[CJDave]

/wwwthreads_images/icons/smile.gif Man, it's about time somebody posted the dual battery system in something besides the written word. There IS one little detail, however that has been in the back of my mind, and that IS....suppose little cousin Leroy sat his butt in your Jeep and played with the headlights, and went off and left them on. the next day, the primary battery is on it's kazooka, and the Jeep won't even fart, much less crank. In that case, the "shoo-fly" around the Hobbs is useless. The pushbutton "shoo-fly" (that's railroadese for SHUNT)needs to get power from TWO sources, and have a diode on each feeder. THAT would be the ultimate setup! And I don't think that I would mix batteries. The secondary battery is supposed to be the accessory battery so you won't play the radio too much, and have to walk home. You can drain it way down if need be./wwwthreads_images/icons/smile.gif Farmjeep, when corn season comes around you are going to have all the national magazines interviewing you, and wanting to know how you thought up all this custom Jeep stuff, yet still continue to feed a hungry nation. Raising food and fiber, folks; that's what it's all about./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.

 

[13337]

That's why I power my oil pressure switch and bypass switch from the SECOND battery, so the solenoid cam be triggered even if the first battery is missing!

Have a look at the diagram again....

(define: 'kazooka' please.../wwwthreads_images/icons/wink.gif)

If Chris Columbus "Discovered" America (with 25 million already here), Can I Go "Discover" Florida?

 

[CJDave]

/wwwthreads_images/icons/tongue.gif I'm still having a devil of a time explaining this to my moonguy /wwwthreads_images/icons/smile.gif crew chief. He claims that the second battery could be down on it's kazooka if Ditzelfritz left the optional hamburger bum warmer on "low" and nobody noticed. So he's saying that to be sure that cranking could take place, that the by-pass needs to get it from either source, with diodes so it won't try to charge, or try to crank the jeep thru the control circuit. Normally, this moonguy/wwwthreads_images/icons/smile.gif is pretty sharp, and he knows how careless his bunch can be about leaving things "on" when they are crocked and hanging around the Jeep. If they have enough beer, then THEY are down on their kazooka./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.

 

[291]

I agree with CJdave's moonguy crew chief. The dead batt would be robbing cranking power from the secondary batt (which is fully) charged. In the ideal situation, you wound want a big ass diode to keep current from flowing INTO the primary batt during cranking only. However, big diodes can cost money, get real hot, and often still break! Even if the primary batt is completely dead, the secondary batt should still be able to crank over the motor, just like using jumper cables. Nice schematic mr rush, that's the way mine will look, no diodes.

/wwwthreads_images/icons/cool.gif Big Ed
'88 YJ, 4" susp,3" body,33's,283 Chevy V8,TH350,4.11's,D30,D35c

 

[13337]

I get what you are saying now! You are saying that if the primary battery is completely 'kazooka', then you are worried that it will absorb the current being produced by the second Un-kazooka battery...

That shouldn't be a problem if you just flip the switch and hit the key.

A completely kazooka battery doesn't have any polarity, so it's just a giant capacitor at first...
It should start even with a completely kazooka primary battery.

If you are worried about someone leaving the override switch on, use a momentary push button, like an old time starter button.

Take a look at the new diagram. It takes the kazooka primary battery out of the circuit entirely... That should stop the problems...
It takes a 1/2" or 9/16" wrench and two minutes before you try to start the vehicle....

If Chris Columbus "Discovered" America (with 25 million already here), Can I Go "Discover" Florida?

 

[CJDave]

/wwwthreads_images/icons/tongue.gif What is the drill if cousin Leroy runs the #2 battery completely down?/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.

 

[Guest]

dave, do you have the diagram i sent ya? this might might be a time to use it. i would post it but i am having problems with my service (cant upload anything).

dan
NECESSITY IS THE MOTHER OF INVENTION
/wwwthreads_images/icons/cool.gifLET IT SNOW/wwwthreads_images/icons/cool.gif

 

[291]

Sounds like a plan mr rush, I can handle that 30sec modification in the event that the primary batt is dead! I like it when a plan comes together, (or did the A-team say that)

/wwwthreads_images/icons/cool.gif Big Ed
'88 YJ, 4" susp,3" body,33's,283 Chevy V8,TH350,4.11's,D30,D35c

 

[CJDave]

/wwwthreads_images/icons/tongue.gif I have it on hard copy, and I don't actually know how to scan anything in. Every time I shut the compooter off, the scanner software goes away./wwwthreads_images/icons/mad.gif

CJDave
I never believe any statistics unless my moonguys /wwwthreads_images/icons/crazy.gif/wwwthreads_images/icons/wink.gif made 'em up themselves.

 

[z50k2]

Just a very simple and quick question...Will the continous hold solenoid fail with constant power running through it? In my previous career as a boat captain I had a parallel switch. This was a momentary on solenoid that allowed the opposite battery bank start the opposite engine using both sets of batteries. Out of habit I always used this switch to keep the batteries up. They were a series of (4) 8 volt batteries on each side. The engines were a pair of 870hp 12v71 Detroit diesels. There was very little room to get around those beasts and swapping batteries was not a fun task. Weekly I would check the battery level and top off with distilled water.
So now my point..
Why not run the batteries seperately, then use a momentary solenoid to start the engine if either battery fails? Then you could use smaller diodes in the charging system to each battery ??? As a habit use the switch to start the engine. One hand on the key and the other on the thick fat button.. Just my thoughts and please give me some feedback..Thanks...
BTW.. I guess it was not such a simple or quick question..sorry..

Ricky...seeya...
1979 CJ-7 401 T18

 

[CJDave]

/wwwthreads_images/icons/tongue.gif Actually, BLACKJACK designed a system exactly like that, everything was manual, and the batteries were connected so as to parallel onto a power bus. It was like a helicopter where you get in and flip the switch BJ's setup was for three batteries, but it could have been one hundred, it didn't matter. If he wants battery number two, he flips "2". The control power was multi-sourced and had diodes to prevent feedback. It was bulletproof, but totally manual control./wwwthreads_images/icons/tongue.gif Oh, yeah....to answer your question. CONTINUOUS HOLD solenoids are made for.....continuous hold./wwwthreads_images/icons/crazy.gif And now how about this little modification....you multi-source the control power using diodes, and the oil pressure switch gets control power from the multi-source circuit. You can also use the multi-source control circuit to bring in the second battery to crank if necessary by using a push button. THIS is the perfect setup. Automatic, yet has all contingencies covered. So take TeamRush's diagram and collect a (+) from each battery with a diode in the line, THEN go to the oil pressure switch, AND have a push button to jump the oil pressure switch in the event that the cranking battery (#1) is on it's butt./wwwthreads_images/icons/crazy.gif THIS is the ideal setup./wwwthreads_images/icons/wink.gif/wwwthreads_images/icons/wink.gif

CJDave
I never believe any statistics unless my moonguys /wwwthreads_images/icons/crazy.gif/wwwthreads_images/icons/wink.gif made 'em up themselves.

 

[13337]

I guess I'm still not getting it. I don't see how the #2 battery could be drained with the engine off on my diagram...
Someone please point out the flaw.
If the engine and override switch are both off, how can #2 get drained? What did I overlook?

I would really like to see the diagram you are talking about with the diodes... Anybody able to post it?
(The best ideas are stolen ones, the R&D are done, so somebody post!)

If you want low cost diodes that will take all charging and load in a vehicle except the starter, try half of the rectifier bridge out of an alternator. Fords work the best for that...

Later folks, and thanks for the help. Aaron.

If Chris Columbus "Discovered" America (with 25 million already here), Can I Go "Discover" Florida?

 

[Guest]

Hey CJDave, if those magazines come after me, I'm pointin' them to your soon-to-be-new residence here in corn country...

Teamrush...if CJDave's moonguy's went wahoo after a few too many brewskis and left the bypass switch on along with the headlights...both batteries would die. It seems to me that this is the only possible way that this could happen. It doesn't really concern me as being a real possibility or anything, though...I suppose that if a guy was real worried that his unattended moonguys were gonna go gonzo on the jumper switch, he could either:
1. Put a padlock on the fridge (but if you lose the key, no beer for you or the moonguys)... or-
2. Use a spring-loaded switch as the bypass switch, so as to never have to worry about dat dere problem.

Measure once, cut twice...or is that the other way around?

 

[z50k2]

What if you got one of those seat switches, like the ones in a lawn tractor. If a moonguy didn't weigh much the switch wouldn't energize, then the button couldn't be pushed, then no dead batttery..How 'bout dat?
Maybe I am gettin' a little silly.. Sorry

Ricky...seeya...
1979 CJ-7 401 T18

 

[Guest]

The last guy who came around this farm and advocated the usage of one of those seat-switches was last seen running north very rapidly with a big, black, male german shepard hot on his trail.

Seriously, we just got a new J.D. lawnmower (the old cub cadet was 27 years old) and we had to spend the first few hours killing the seat switch and the backup-mower cutoff switch.

Measure once, cut twice...or is that the other way around?

 

[Guest]

Guys ,I don't know what all the hububb is about here. I've been using a second battery setup in my jeep for ten years.It is controlled by a toggle switch to a continuous duty relay ONLY. REPEAT,TOGGLE SWITCH ONLY.The switch is powered directly from the relayon the primary side. Here's a step that I bet that no one has thought of LOCK THE DOORS AND KEEP LITTLE COUSIN LEROY OUT!!! My toggle switch has a little light in it to remide me to turn it off when I exit. Since I'm the only butt that is allowed in the driver's seat, there is no problem. NUFF SAID

Gorgeous George
Jus'luvJeep'n/wwwthreads_images/icons/cool.gif/wwwthreads_images/icons/wink.gif
ASE Master Tech