can someone post up some pics of a dual battery try installed? has anyone made there own battery isolater? who makes a relay(solenoid) that big? can i just use an ignition solenoid? a wiring diagram might help simplify this fun!!
Wrangler products have a pretty good set up for dual batteries. Here's a couple of pics of my home built set up. I used the factory braces and straps and built a new tray.
Wrangler Products tray (bought it used for cheap), Hellroaring isolator/combiner (bought it slightly used for cheap), all cables replaced with heavier gauge:
This is one of those subjects that everyone has an opinion, and there are a lot of 'Right' ways to do dual batteries.
Depends on your application, so give your application some thought...
1. Just plain old duals, with out external charge isolators.
This is for the guy that wants Duals in temperate conditions.
(The easiest way to do duals)
Here are the 'Rules',
You MUST use to batteries of the same age, size and kind.
If there is an age difference, the newer battery will boil dry before the older one gets fully charged.
If you run two different SIZE batteries next to each other, the smaller one will boil dry before the larger one gets fully charged.
If you run a 'Starting' battery next to a 'Deep Cycle' battery, the Deep Cycle will boil dry before the starting battery gets charged.
*IF* you run the same AGE, SIZE, KIND next to each other, you can connect directly to your alternator and not need a charge isolator.
Since this diagram doesn't allow for dual starter solenoids,
This wouldn't be a good deal for someone in cold weather since a single starter solenoid is fairly restrictive and doesn't allow the doubled amperage to get to the starter.
2. This is an idea for a guy that wants to have one battery in reserve.
Wiring this way, you will isolate one battery when the engine stops running, so if you leave lights on, or the kids play in the jeep and turn something on, you can jump start yourself...
This is also a mild weather dual rig, since there is only one starter solenoid.
Once again, since you aren't using a charge isolator, the batteries will have to be the same Age, Size and Kind.
And this is about the same as this set up if he has an automatic solenoid circuit,
Pretty good cables on this rig! Most home builds are little, goofy, made in china store bought pieces of crap, but THESE are some REAL cables!
3. This is for a guy living in cold weather areas, when double the amperage to the starer would really be a good deal!
Again, this is with a single charging source, so the batteries need to be the same Age, Size, and Kind.
This has TWO improvements over the above wiring styles...
1. There is a starter solenoid for EACH battery, so the amperage to the starter is doubled.
2. This uses a smaller Oil Pressure Switch for a charge circuit instead of a large continuous hold solenoid, since there are two starter solenoids, there is no large drain from one battery to another.
With the solenoid this system is self isolating when the engine shuts off.
The Oil pressure switch was designed to run a fuel pump and a choke heater, so the relatively small amperage draw from the second battery is not a big deal.
By just adding a dash switch, you can self jump start with out ever getting out of the drivers seat in case you ran one battery down...
This is a little more complicated,
Since it's a design for guys that have high output alternators, or use large drains on their batteries (like winches, ect.).
Deep discharge of batteries will require a larger amperage charge to replenish them.
This system is designed to meet three requirements,
1. Trail Redundancy/Availability Of Spare Parts.
There must be two solenoids, two batteries, and they must work seamlessly.
Parts must be readily available at most any auto parts store.
2. It must be able to charge the second battery to the limit of my current alternator.
The alternator is a 78 Amp Delco 10 SI series.
3. It must be self isolating when the engine isn't running,
and self jumping in the even of a single battery getting totally run down or failing.
Looks complicated, but isn't, and was achieved with off the shelf parts except for battery cables...
Here is the same system, but with an oil pressure warning light or buzzer if you need one.
Since it comes with the Oil Pressure switch I use, Why not?...
If you decide to run different Age, Size, or Kind batteries together,
YOU MUST USE A CHARGE ISOLATOR!
Some people use a starting battery with a deep cycle battery, or have batteries in the back of the jeep for rear mounted winches or power inverters, ect...
Most isolators will allow for up to four batteries, but keep in mind, you are going to loose about 1.5 Volts from alternator output for each battery, so I recommend you use an alternator with an adjustable regulator, so you can compensate for the losses in the isolator...
Here is a simple diagram of how that would hook up.
Now, the first thing you have to remember is, I'm cheap.
I won't buy any of the after market crap unless there is just no other way!
Second is, I'm into convince.
I don't like beating my self up when it's just not necessary.
To that end, I present this,
I'm an avid off roader, but I live where there is TONS of mud, like it or not.
Mud and cheap gauges don't get along, so the expensive part of this is the gauge.
About $15 from Summit.
Liquid filled means no water/mud/sand can get into it like the cheap ones get.
The rest is off the shelf or home made...
Notice in these diagrams I use an oil pressure switch that isn't 'Stock' for Jeep.
In this case, I use one from a Chevy pickup that normally starts the fuel pump, and heats the choke, so it's got plenty of current carrying capacity.
It also has the ground switch for your oil pressure 'Idiot' light.
The high pressure oil pressure 'Whip' is from a grease gun.
4,500 PSI capable, designed for petroleum, with the correct pipe thread ends for $5 at NAPA. (having one custom made is about $30!)
That gets the oil pressure up from the side of the engine to a more reasonable location...
Scrap aluminum about 1" thick. Drill, $6 pipe tap and cutting oil.
Notice there is a version for electric gauge sending units so they can hang over the fender?
You will need a pipe plug for the gallery end with that version!
If you aren't using an electric gauge (and I'm not) then it's time for a reasonable line to the mechanical gauge... $8 with lots of fittings from Advance Auto.
Now you can reach/service all your electrical without burning yourself on the headers!
Once again you amaze me! That is a killer write-up! I'm doin' one this weekend...
Application, Application, Application!
Some guys need lots of cranking amps for cold weather, others just want to have a back up, and some are just making a 'Statement'...
I need trail redundancy, and I need power to a winch and inverter, plus, I weld off my batteries, so that is another requirement (we haven't covered yet)...
What is the Original Posters 'Application' so we can determine 'Requirements' and maybe help with a tailored diagram for his purposes.
How much do you think setup #3 would be. I am running a manual oil pressure guage and dont really understand the purpose of the oil switch in the setup.
Jeephammer - Christ sakes. I'm amazed at your mechanical insight. Where in the heck are you at in Indiana? I'm located between Lafayette and Indy on 65, close to a little town called Thorntown.
You don't want fuel pumping into a vehicle after a crash, so if the engine stopped, and the oil pressure drops, it opens the circuit.
We use it to isolate the second battery when the engine shuts off.
Both batteries are tied together to charge/discharge when the oil pressure is up (Engine running),
When you shut the engine off, or the engine dies, oil pressure drops and the second battery doesn't discharge.
*IF* your primary battery isn't discharged,
When you hit the key switch, both solenoids will send CRANKING amperage to your starter.
When the vehicle starts, and the oil pressure comes up, the oil pressure switch will connect both batteries so the can both charge.
*IF* Your primary battery is DISCHARGED, (Left the dome light on or something else on in the vehicle) you can self jump start by using the dash switch listed in diagram 4.
Since it's a 'Momentary' switch, you can't 'Leave it on accidentally' and run both batteries down.
This is handy if you use radios at your camp site, have kids that get into things, have equipment that likes to slow drain things...
It also beats having to get under your hood on sub 0° days to hot wire the solenoids so you can jump start your self!
The idea of the momentary is to supply power to the fuse box and starter switch even with a dead primary battery.
You are just jumping some power over to the fuse box power feeds so you can get the starter solenoids activated, and they, and the oil pressure switch will take it form there for you!
You have problems getting started pretty often, have a winch, or are going to discharge the batteries deeply with an inverter, welder, or some other device...
The 5th diagram is really the best way to do this if you think you are going to have problems or deeply discharge the batteries...
A heavy duty lighting/accessory relay, still automotive size, since you only need about half of your alternator maximum output, which is usually about 30 or so amps...
Most light relays at the discount stores are rated for 25 or 30 amps, and you are not going to see that maximum charge very often...
Is triggered by the oil pressure switch OR by a dash switch to connect the two batteries via a 10 Gauge wire in the diagram.
Since I have a 78 amp alternator ('79 Pontiac full size), technically, I should never see more than about 40 amps at the relay (78 amps divided by 2 batteries),
But I like to over build things for reliability and redundancy.
My relay is shown here, (along with the socket, and some pressure swtiches.)
It's rated for 160 amps (take a look at the really contact blade size!) and it will do roughly 70 amps all day long with out failure. 8 Ga. input, two 14 Gauge outputs and only about 1/4 amp to trigger!
This particular relay and harness come from an electric air compressor set up, so you just KNOW they have to be stout to cycle a compressor several hundred times a day, every day!
SO, now that you have two complete (and redundant) battery & starter solenoids,
And seamless operation of both,
A way to isolate the second battery, Charge the second battery that is 'Hands Free',
A way to jump start yourself at the push of a button, you are pretty well set for the most severe trail, work or camping adventure.
The cost is reasonable.
Since you already have all the wiring for one battery, cables, solenoid, ect,
You need the cables for the second battery (make them good ones!, about $30 for custom made),
An extra starter solenoid (about $10),
An oil pressure switch, (under $10),
And a relay and socket ($13 for common lighting relay & socket)
Dual battery tray, I made mine from angle iron, $10.
It's the two new matched batteries that are going to cost you plenty!
With the price of lead, and the price of transporting something that heavy, even the 'Economy' batteries aren't cheap!
Can't say what they will be in your area, since local transportation, recycling fees, ect, all play a part in the costs.
My two BCI 24 size batteries were about $40 each.
http://www.batterycouncil.org/ (Lean about batteries)
Ease of this project, I'd say about a 5 on a scale of 1 to 10.
There is meal fabricating (battery tray and tie down) and some wiring that most people aren't familiar with, so getting used to crimping tools, solder, heat shrink can be a real pain for some people...
Again, I recommend you use WELDING CABLE for battery cable! Much more suited to large volume DC loading than thicker strand, vinyl insulated, and smaller sized 'Battery Cables' sold at the discount stores!
And don't forget to move the primary battery ground down to a starter bolt!
This will help your starter get the current it so desperately needs, especially when it's cold and all those metal parts the ground has to jump through have contracted from the cold!
About 50 miles up Hwy. 57 from Evansville.
No formal education, but (obviously) some practical education from different jobs...
It's funny the stuff you pick up in some of the oddest places!
Nothing really new here, I'm just swiping the best parts (or in some cases the only usable parts) from stock vehicles and making them work for Jeepers.
After the Dumpster diving and short cuts AMC did, we AMC drivers and CJ guys need all the help we can get!
What are your thoughts on using a wire from an electric stove or dishwasher (220's)? Also, why do we want to use fine thread wires (dosent resistence increase as diameter decreases), is it because of flexability? I think I understand what I need to do to do the dual battery setup even the fuseable links....maybe. I think that I have a short somewhere and I want to find out where it is (everything works as far as I can tell) before I do the dual batteries(good idea or not?). I cleaned my contacts on the battery terminals, starter solenoid, and body ground tonight, also changed the oil to 5w-30 from straight 30. Maybe tomorrow it will start and not only give one half a** attempt to start before the battery dies and I have to jump it.
To do the dual starter solenoid setup, the only difference from picture 3 would be a "Y" with one wire going from the + terminal and the other two wires going to the hot sides of each solenoid?
AC is usually a lot more expensive than DC stuff also.
See, larger wires leave larger air gaps between them.
The finer the strands, the denser the pack, and the more current the wire will carry.
I don't use just ANY fine strand, For battery cables I use WELDING CABLE.
Fine strand means more amp carrying capability
(think about what a welder does! Direct short all day, every day, and that takes some real amp loading capability!)
Welding wire is usually virgin copper, since there is no alloy in the wire, it carries amp loads better.
Most of the discount, off the shelf battery cables are alloy, and the added crap makes them not only weaker when it comes to amp loading, but they corrode faster, and they corrode inside the insulation.
Fine strand means easier to work with, bend and locate.
Welding cable uses Flame 'Proof' insulation. (anything will burn eventually, but this stuff is tough!)
It's designed to be around molten balls of weld slag all day, so under hood heat won't affect it like the heat will wire with vinyl insulation.
Welding cable is dragged across greasy, concrete floors all day, and over sharp metal edges all day.
The insulation is abrasion resistant and chemical resistant way better than vinyl insulate automotive wire.
Since industry demands welding cable in volume, it's cheap to us where custom 'Stereo' cables are of lesser quality and more expensive.
Do you have a 'Short' as in 'Short Cut To Ground' as in battery running down?
Do you have an 'Open', as in 'Open Circuit', broken wire, popped fusible link, ect?
Moving your battery ground wire to the starter mounting bolt would be another good thing to do...
Make sure your starter gets a good ground, NO MATTER WHAT!
I'd also consider having the charging system tested.
Most of the autoparts stores will do that for free now, if they aren't just crazy busy...
Don't let them talk you into a new battery until you decide if you want dual batteries yet!
One BIG HONKIN' battery can cost as much as two economy batteries, but two economy batteries will give you more total energy...
If you wire both solenoids to charge together with out any way to isolate them, they will both DISCHARGE together if you leave a light or something on.
If you don't care about this, just leave the oil pressure switch out and use a 10 Ga. wire jumper like you are talking about.
I have a tendency to leave lights on, and crap like that, so I use an isolator....
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