Dual battery Installation

Discussion in 'Technical write ups & Installation Guides' started by JKmotorsports, Oct 8, 2007.

  1. JKmotorsports

    JKmotorsports tahoeyukonforum.com

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    Well, installed a second battery this weekend, so here is the write up for the installation. Only thing is, some of you may be disappointed, as my wife had the camera when she was out, so I was unable to take pics during the installation. But i did manage to snap some after shots when she she returned home.
    I'm using the aux battery to help power the high current stuff such as my 3000 watt power inverter, 5000 watt mono amp, etc. Right now I'm using the same cca/rc rating battery I had laying around and will be upgrading to Optimas later.

    Parts
    1. You will need a way to mount the new battery. Probably the easiest way to do this is to get a stock replacement battery tray with the retainer and retainer bolt.
    2. Battery Isolator/relay. This will prevent the main battery from draining while the engine is off and your accessories are running off your aux battery. Note: If the key is in the acc position, the stock electrical system will continue to run off the main battery. Also, in the ign position, the isolator contacts are closed and power will be drawn from both batteries. In this instance, you will get power from both batteries, theoretically doubling reserve capacity.
    3. Cables to connect the main battery to aux batt. I used about 12 ft of 4 gauge to run from positive to positive and two feet for ground.
    4. About 14ft. of 18-22 ga. wire to activate the isolator. The isolator needs to be connected to a source that will turn the relay on while the eng is running so both batteries will charge.
    5. Sidepost battery extender terminals(3), found at most car audio shops.
    6. 4 ga. ring terminals, (6)
    7. 18-22 ga. ring terminals, (3)

    Tools
    You will need an assortment of sockets, cordless drill/screwdriver with #2 phillips bit, asst of open end wrenches, digital multimeter, solder and soldering torch (or small hand-held propane torch if available).

    Here are some pics to show the location of the battery and isolator, cables, etc.
    [​IMG]

    [​IMG]

    Here is the cable routed in the front:
    [​IMG]

    Battery Isolator and fuse/fuseholder
    [​IMG]


    1). First, you will need to remove the fender to cowl brace on the passenger side near the hood hinge. There are four bolts; two attached to the cowl and the other two on the fender.
    2). Mount the new battery tray in the area below the brace, on top of the fender well. There are no mounting holes, so you will need to screw the tray down with some self-tapping screws. Or you can remove the front wheel to drill new holes and use nuts/bolts to attach the new tray.
    Set the new battery in the tray and secure.
    3). Find a suitable place for the battery isolator. I mounted mine on the firewall, right above and to the left of the a/c accumulator. Be sure placement does not get in the way of the new battery. You can attach this with some self-tapping screws and your cordless driver:
    [​IMG]

    4). Now, you will need to prepare the new cables. Cut about 1 1/2 feet off the 12 ft cable. You should now have about 10.5 ft of cable, one 1.5 ft section, and about two ft for ground. Attach each end of each cable with the 4 ga ring terminals. I soldered all my ring terminals using a propane torch and solder, then used heat shrink to insulate the connections. I used a propane torch because it heats the larger terminals and cable much faster for the solder to flow better. You will also need to attach a smaller ring terminal to one end of the smaller ga. wire used to activate the isolator. Next, cut off about 2 ft or so from one end of this wire. Attach the other two smaller ring terminals to each end of this shorter wire.
    5). Attach the shorter section of 4 ga wire onto one terminal of the battery isolator. Follow the instructions that came with your battery isolator as to which terminals are which. They should all be the same, with two large posts and two smaller posts. The cable will attach to one of the larger posts (either one). Next, attach the other end of the cable to the positive terminal of the new battery using one of the sidepost battery terminals. You can also attach any cable you may have for your accessories (amp, etc) now.
    6). Attach the longer run of 4ga cable to the other large post on the isolator. Also, attach the smaller 18-22ga wire on one of the smaller posts of the isolator (again, either post). Route this wire along with the cable down the passenger side, across the front over the fan shroud, and to the main battery. If you have split loom available, slip the loom over the cable and wire before routing. Be sure to route the wire as neatly as possible and as not to interfere with the airbox removal or any other part. Secure the cabling with wire ties, cable mounts, etc. as neccesary.
    7). Now connect the end of the 4ga cable to the positive terminal of the main battery. To do this, you will need to remove the stock terminal and replace it with one of the new extended terminals so that you can fit the new cable on. Secure and tighten the post.
    8). You will need to use a test meter to find a 12V source that powers on with ign only. The end of the smaller gauge wire will attach to this source. I attached to an ignition wire coming from the fuse block harness. You can simply attach to an appropriate fuse in the box with a fuse tap, but the preferred method is to splice into an ign source wire and solder.
    9). Now, connect the short length of the smaller gauge wire to the last small terminal post of the isolator. Leave the other end loose for now.
    10). Connect one end of the ground to the negative terminal on the battery using one of the new sidepost terminals. Route this and the loose wire from the isolator to an existing bolt on the body (fender, firewall, etc.) and connect to ground. Option: I also used another length of cable from the battery ground to the frame to ensure lowest possible voltage loss from battery to chassis.
    Go through and make sure the cables, battery, all connections, isolator, etc. are all secure. Test operation of the isolator by turning the ign key to the ignition position. You should hear the isolator click on and off when the key is turned from ign to off positions.

    Option: I also upgraded the stock 8ga wire from the alt to main battery with a new 4 ga wire, and added a beefier ground cable to the main battery.

    I hope this is informative. These are general guidelines, as wire gauge, parts, and placement may be different depending on specific application. And please feel free to chime in if it's obvious I missed anything (long post, so I might have gone off track somewhere. I've already edited 4Xs:))
     
    Last edited: May 29, 2008
  2. Coastie Kyle

    Coastie Kyle Full Access Member

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    Nice
     
  3. riceplanter

    riceplanter New Member

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    JK, very informative! Now I know why my extra battery was losing power, which led to alternator failure! Where did you find your isolator/relay? I noticed that you had a twin fan setup! What brand did you install and how is working for ya? It looks like it fits perfectly! Overall your engine by looks stock, you made everything look like it belongs there from the factory!
     
  4. JKmotorsports

    JKmotorsports tahoeyukonforum.com

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    The relay is PAC. I got it through one of the vendors at a shop I used to work at a while back. You can find it on-line or at a local stereo shop (not Best Buy or Circuit City type). The fans are 16" Proform. They work great. Check Summitracing.com, Jeg's.com, places like that.
     
  5. riceplanter

    riceplanter New Member

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    Thanks! U da man!
     
  6. chwnn255

    chwnn255 New Member

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    Gentlemen... Absolutely a terrific site! I have been all over it for the past few days and it's one of the best I've been on. Kudos...

    Question: Need some product and install advice/help on a 2003 Yukon XL SLT I am replacing ALL "Blows" (love that!) OE with aftermarket toys. Here's the toys I have so far... all are ready to go for install.

    1. Kenwood DNX 7100
    2. Directed Audio D2205 AMP - 5 channel ESP Hybrid 2200 watts Max
    3. Polk Audio MOMO C400.4 AMP - 975 watta MAX
    4. Polk Audio SR6500 Front ...AND Rear!
    5. PAC SWI-JACK Steering wheel controls (top retain existing wheel functions)
    6. 170 deg Rear Backup Lincense Plate camera with IR
    7. Sirius SC-C1 - Sirius satellite programmable tuner & antenna
    8. Kenwood KCA-SR50 - Kenwood Sirius adaptor
    9. Kenwood KCA BT100 - Kenwood Bluetooth adaptor
    10. Kenwood KCA iP200 - Kenwood AUX adapter plug/cable
    11. Viper XV 160 Remote start
    12. GM DD kit for mounting/installtion of aftermarket HU's
    13. Metra VT-GMOS-04 GM Class II Data bus Interface - Retains factory chimes, functionality, etc when replacing HU.
    14. 50 Sq Ft of Dynamat FatMat Auto sound deadener for doors and..????
    15. Sub ... this is still an open item and leads me to my first question...well

    ...several questions:

    1. What the he** do I do for a subwoofer and still retain a factory look and storage space? I've looked at JL Audio's Stealthbox ($699 + install ...ouch!), MTX Audio's Thunderform (MTX isn't up to snuff music-wise...or are they?... with my other equipment so $299 + new sub speaker + install... ouch again!), and SuperCrew's under the rear seat box won't work 'cause I've got Captains seats in the 2nd row. HELP! Would LLooovvvve to figure out how to utilize the driver's side rear storage back panel which means I'm leaning the MTX route ...any suggestions? Would be happy with 8" or 10" sub... however a Polk Audio SR124-DVC 12" would be ideal! (it's Top Mount Depth is 19.30 cm or about 7 9/16")
    2. I bought two Amps to see which one would sound the best... the one from Polk will probably win out, but the Directed Audio Amp is a bad boy when it comes to programmability, controls, flexibility... basically geek-factor stuff. What is your opinion(s)?
    3. Do I need a 2nd battery and all the relays, capacitors, fuse boxes, etc. if I only run this setup while driving 99% of the time?? Or just an uprgraded alternator or is that even overkill? I'm a Regional Manager and travel 18 states so I spend a huge amount of time in my ride each week.
    4. Am I missing anything? I'm trying to go for a first class setup without being stupid with my hard earned cash ...like buying all McIntosh equpiment ($11,000.00 for what I have) and Morel speakers ($2995 for a pair). Or silly looking 'cause I take clients out all the time.

    I know this was long, but I am ready to get these toys installed next week and the guys I'm gonna have do it aren't cheap and need EVERYTHING all at once... which makes sense. So anyone's experience/help/advice would be appreciated.

    Chwnn255 says... thank you!
     
  7. brdnboy

    brdnboy Full Access Member

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    Well im not a ton of help on everything, but i do have a double din unit installed. If you do not yet know which dash kit to get, the metra 99-2003 is the best i have seen. It looks as close to factory as possible. Also, i have seen a sub installed in the rear driver side, where that fake sub grill is. It may have been on this site or another, no matter someone will probably link it. It looked sweet. If this is not the route you go then the infinity basslink series may work, or there are numerous shallow mount subs that would not take up much room at all in a box. If your car is always running, an extra battery may not be an issue, but heavier ground an power from alternator might help. I would do an extra battery just cause it is so bad ass. (Thanks JK) On #13 you mention the GMOS-04. I have experience with this unit and would not recomend it. I just changed from it to a PAC OS-2 and i am much happier. It is a much better overall product, with better support.

    Thats about all i can help with. Let me know if you have any specific questions, otherwise many other people on the forum will chime in with much more detail.
     
  8. chwnn255

    chwnn255 New Member

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    Thanks... What kind of issues did you have with the GMOS vs the PAC OS-2? I got the item off Crutchfield ..even paid more so I COULD return it if there was and issue... was it glitchy?
     
  9. brdnboy

    brdnboy Full Access Member

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    I used the GMOS-04 for quite some time. I wasnt really disapointed till i saw the performance of a PAC-OS2. The PAC constuction is better overall, seems less gimmicky and flimsy, with better technical and customer support. The issues I had with the GMOS are as follows:

    1. Engine Noise; no matter how i grounded it and what i did there was and engine noise that increased with speed. Very annoying.

    2. Chimes; worked fine except for memory seat buttons gave no chime for setting, or recalling seat position.

    3. Volume; the GMOS has a volume nob, but as you turned it up the enginie noise got worse, so i found a happy medium of loudness and engine noise. Not a compromise i wanted to make.

    4. Popping; I dont know what caused this, but if i was sitting in my car for 10 minutes and RAP shut down the radio, once in a while when i turned the key to turn the radio back on there would loud pops in the speakers, and then the engine whine would be horrible, like the GMOS forgot its settings and turned the volume all the way up on its own. Obviously an issue with Class 2 databus and the GMOS, but i have no idea.

    That about covers my issues. Nothing major but enough stuff that i was fed up. When i installed the PAC, every issue listed was resolved. The unit has worked flawlessly so far.
     
  10. puckhead

    puckhead Full Access Member

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    JK, I noticed that you took out the small support beam that is pointed to in the pic below. Have you noticed that if it had had any effects since you took it out? I do a decent amount of driving on rocky bumpy dirt roads and was curious if it would have any effect on the rest of the truck. I have the 2001 Tahoe LT also. Thanks in advance

    [​IMG]
     
  11. greengumby

    greengumby Full Access Member

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    just a question about the alt .. by installing a secondary batt your now doubling the current withdraw from the alt to charge the two batts thus increasing the time for alternator failure did you upgrade the alt or how did you over come this ?

    in plain terms i'm trying to say is that you have a checking account as the battery and the alt is the 500 dollars you keep over drawing the account you open up another account as the second battery but your still feeding off the same 500 bucks :)
     
  12. Gambler

    Gambler Full Access Member

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    Wow, that is a monster battery, isn't it...
     
  13. 1CLNTHO

    1CLNTHO New Member

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    Awesome post man very informative, now i have a project for next weekend!
     
  14. tast101

    tast101 Full Access Member

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  15. TangibleGhost

    TangibleGhost New Member

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    Quick questions: 1) Is it bad if the alternator is rated higher than the battery isolator? and 2) How much power would that big ass 250 amp pull from the motor?
     
  16. tast101

    tast101 Full Access Member

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  17. thdrill

    thdrill Full Access Member

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    Not to hijack the thread but a quick question...I am currently attempting to hookup a second fuse box for some emergency lights I am looking to install, basically only want them running when the engine is on and no other times (alternator was the easiest fix I could find). I currently have the Big three wiring mod in place and am concerned that with the positive hookup from the battery to the alternator that the wire from the alternator to the fuse panel will stay on even if the engine is off. Now the question...will an isolator help alleviate this problem?

    Paul
     
  18. JKmotorsports

    JKmotorsports tahoeyukonforum.com

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    Depending on your power needs, you can use some 30/40A relays or a larger 200A battery isolator/relay. You can run power from the battery to the relay(s), then to the fuse block. The coils in the relay will be triggered by an ignition input to allow the relays to close the circuit and feed power to the fuse block only when the key is in the ign position.
     
  19. JKmotorsports

    JKmotorsports tahoeyukonforum.com

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    Doesn't work that way. As long as the voltage from the alternator is higher than the nominal voltage of the batteries, the batteries will charge without damage to the alt. The batteries don't draw current from the alternator, but rather voltage is being "pushed" into the batteries by difference of voltage potential. If the electrical current demand of your electrical system constantly exceeds the output of the alternator, then you can fry the rectifier and destroy your alternator.
     
  20. pervitizm

    pervitizm New Member

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    I have a question regarding this. I have a 07 Suburban that I want to install a second battery in for my stereo. Where can I get an 200A battery isolator at that will work with my truck? I'm leaving the factory battery in and installing a Optima Yellowtop 800CCA battery.

    Thanks to those that reply.