Double Battery Setup And How To??

[BIG-G]

OK, i DID the search and came up empty on what im lookin for so heres the thread and its question, im runnin a yellow top now as it is and want to run 2 yellow tops with a serious alternator. Now i got the alternator all covered but im clueless on how to set up a double bettery system and i want them to be both working at the same time. Im gonna be drawin a sh*t load of amperage and i want my XJ impeniterable to anything i can do to it so PLEASE if anyone has LINKS, to products for this or any info, id greatly appreciate it!!

 

[BLSXJ]

When I mounted my dual exide's in the back I wired themin parallel. positive to positive neg. to neg. however I did add a dissconnect switch between the 2 batteries on the positive cable. that way I can drain one battery down then flick the switch and I'm back to 100%. I normaly run with both batteies "on" unless I know I'll be needing a "safety net" l8tr.

remember to use quality heavy gage cable and strink wrap all connections

 

[Matthew Currie]

For the simplest way, do as BLSJ says, just wire them in parallel. You'll have the same voltage, and the two amperages added together. Of course if you do run them down, though, they're both dead at once. For this to work best you also need for both batteries to be similar in condition, because they will "float" together. A weak one will pull current out of the strong one.

Alternatively, there are pretty standard isolator systems made for boats and RV's. A lot of people who use heavy-drawing equipment isolate the two batteries, letting one be the equipment battery, and the other the normal car battery (on a boat you might have the starter battery and the one that powers running lights, cabin lights, etc.). The alternator feeds them both through diodes so they don't float together, and they are separately wired to their loads. You can also then use a switch to gang the batteries together, or choose one or the other for starting, thus ensuring that you'll just about always have power to start. An advantage of isolation is that you can use different batteries, including one old and one new, one regular and the other deep-cycle, etc. and not worry about how they interact. Check RV dealers or marinas for isolators and switches if you want to make a really sanitary job of it.

A simple home-brew dual battery setup can be done simply by attaching battery two (the one that might ordinarily power the winch, etc.) to the main positive line through a starter solenoid (old Ford style firewall-mounted solenoids work for this), with a hefty diode bypassing the solenoid to allow charging from the alternator. When you need a boost, you push a button, the solenoid connects battery 2, and off you go. You can't run the batteries together for very long this way or the solenoid will cook, but it is a quick and easy way to make battery 2 available for boosting.

 

[BIG-G]

OK, let me see if i got this down correct. First i have the yellow top optima to start and will get a second one!! Second, the higher amperage alternator will be in effect.
NOW for the wiring. SO, ur saying i can just run the "thick" power wiring positive to positive terminals and then just ground them both real good? BUT its best to get a solenoid or, "BIG RELAY", to wire up in the middle between the 2 batteries, so the positive wire hits the solenoid first then off to the secondary.
Anyone have a link to a solenoid, "BIG RELAY", one that is good quality to do the trick?? NOW, when i wire in stuff, i can wire the winch straight to one battery with the KC daylighters and maybe the stereo system??? Then the other battery can be wired up to the vehicle itself and use its power for the XJ itself.
OK question on who gets the alternator connected to? OR is this in the solenoid/BIG relay thingy??? If anyone has links and or pics for these setups id appreciate it alot and i also thank you 2 for the info cause its gonna be goin in soon. I'll take pics, (when i have the $$)!!! THANKS AGAIN!!!

 

[1989laredoxj]

hey first off why are you wanting to use 2 batteries, you may not have to but either way here is a link I found it isnt very discriptive but you can see the picture and how the hooked it up, http://www.rockcrawler.com/techreports/kilby_dual_battery_TJ/index.asp
If you hood these up incorrrectly you can make 24volts and short out all of your electrical so be sure you run these parralel and not crossed.

 

[BIG-G]

hey first off why are you wanting to use 2 batteries, you may not have to but either way here is a link I found it isnt very discriptive but you can see the picture and how the hooked it up, http://www.rockcrawler.com/techreports/kilby_dual_battery_TJ/index.asp
If you hood these up incorrrectly you can make 24volts and short out all of your electrical so be sure you run these parralel and not crossed.

OK, seems real easy exept my yelow optima is a few years old and id be buying a new one. I could sell it and get 2 new red ones to equal tem out but i got a bigger question!! The batteries are gonna be on seperate sides of the jeep, the stock location and the airbox location so is that gonna matter??? Plus as u said im still worried about them shorting each other out somehow without a relay/solenoid of sorts!!!
MORE INFO!!!(thanks tho!)

 

[1989laredoxj]

You shouldnt need to sell the old one just get it recharged and then hookit up. I will post shortly some more links.

 

[1989laredoxj]

this may help a little bit looks like there is a lot of information here
http://www.safari4x4.com.au/80scool/tech/dual_batteries.html
and here is another one
http://www.sierrajeep.com/dual.htm
with a lot of information on it. Hope that helps

 

[Matthew Currie]

OK, let me see if i got this down correct. First i have the yellow top optima to start and will get a second one!! Second, the higher amperage alternator will be in effect.
NOW for the wiring. SO, ur saying i can just run the "thick" power wiring positive to positive terminals and then just ground them both real good? BUT its best to get a solenoid or, "BIG RELAY", to wire up in the middle between the 2 batteries, so the positive wire hits the solenoid first then off to the secondary.
Anyone have a link to a solenoid, "BIG RELAY", one that is good quality to do the trick?? NOW, when i wire in stuff, i can wire the winch straight to one battery with the KC daylighters and maybe the stereo system??? Then the other battery can be wired up to the vehicle itself and use its power for the XJ itself.
OK question on who gets the alternator connected to? OR is this in the solenoid/BIG relay thingy??? If anyone has links and or pics for these setups id appreciate it alot and i also thank you 2 for the info cause its gonna be goin in soon. I'll take pics, (when i have the $$)!!! THANKS AGAIN!!!

The "quick and dirty" setup I mentioned above is only good if you use the second battery as a booster, rather than as a source for a winch, etc. You have the first battery installed as usual in the vehicle. The second battery is grounded normally, and the positive is connected to the positive of the other battery (or a common terminal elsewhere) through that big solenoid, so that it is only connected when the solenoid is engaged. However, bypassing that solenoid is a big diode, oriented so that current can flow from the alternator to the second battery, but not from the second battery back to the first. This will work if you need the second battery only as a booster. You can now run down battery one, and just push a button to get a boost. However, if you plan to load the second battery heavily by itself, the single diode arrangement will let the primary battery discharge into it, which kind of defeats the purpose. If you want to ensure that neither battery floats its charge to the other, you need a dual-battery isolator, which essentially puts a diode in the charging path of both of them. You can buy these ready-made, and I'm pretty sure they include instructions. Before you reinvent the wheel, I think you should visit an RV dealer and see what's on the shelf.