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Adding a second battery '15 GMC

Discussion in 'Chevy Trucks' started by Motorman 007, Oct 9, 2014.

  1. I'm going to put a second battery in my new '15 GMC 2500HD. There is already a battery tray and hold down installed in the truck from the factory. My question is...I have the camper provision already wired in the truck with the termination coiled up on top of the fuel tank. Is this already wired into the truck or are there terminations under the hood somewhere that I need to connect?
    I've read the dual battery sticky. Do most of you just connect the batts together using one or two gauge cable or do you isiolate them?
     
  2. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,926

    What does the wires on top of the fuel tank have to do with dual batteries?
     
  3. It doesn't really... other than in my previous trucks some of the wiring including the trailer brakes and 12V feed weren't connected from the factory and if I needed to do that, I would connect it to the second battery.

    Did you have something constructive to add??? ;);)
     
  4. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,926

    Yes Francis I do
    Pos to.Pos neg to frame, engine block, accessory bracket, or other stout piece of metal. When making your end it's always better to use copper ends and to solder them. Proper heat shrink tubing as well covering well past the end of the eyelet.
    When attaching the gnd to the "place of contact" wire wheel or scrape off any paint or undercoating that is there. I personally like to put a dab of dielectric grease where I cleaned down to bare metal due to the rust factor.
    Not sure what your positive battery clamp looks like but you may have to buy a new one or attach the 2nd batt cable elsewhere. In which case a pic would be needed
    Usually an isolator isn't necessary, and 2g cable should be sufficient
     
  5. calhoun

    calhoun Senior Member
    Messages: 165

    If you use your camper for rustic camping (no hookups) I would isolate. You can then run your fridge, lights, sounds, etc off the battery and still have a fresh one to start the truck with in the AM. I have a 2500watt inverter hooked to my isolated battery I then plug in the camper as if I do have hookups without the generator noise.
    For plowing just hookem together.
     
  6. snowymassbowtie

    snowymassbowtie Member
    Messages: 75

    If you connect

    the batteries direc to each other they should be as close as possible in age size etc. Even if the truck is new the battery could be 6 mos. old. The best way to add a second battery would be to run the second battery positive to a constant duty solenoid powered by key power and then your ground as mentioned above. If the batteries are not the same one will destroy the other
     
  7. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,926

    What's the point of the solenoid when going batt to batt?
     
  8. Whiffyspark

    Whiffyspark 2000 Club Member
    from SOMD
    Messages: 2,402

    I would just buy the harness and hold down from the dealer. You dropped 40k what's a couple hundred lol
     
  9. I dropped a whole lot more than $40K on this beast.....The battery tray and hold down are already in the truck. I just need the cables. Thanks
     
  10. snowymassbowtie

    snowymassbowtie Member
    Messages: 75

    What's the point of the solenoid when going batt to batt?
    Your not connecting batteries directly. they are wired thru the solenoid.
     
  11. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,926

    So what's the point of it? That's my question?
     
  12. SnoFarmer

    SnoFarmer PlowSite Fanatic
    from N,E. MN
    Messages: 8,445

    "Adding the duel batteries connected directly together and upgrading the stock charging wire and ground cables will allow the system to operate at peak efficiency and allow the alternator to provide all the amperage it can to keep the batteries charged."

    and
    When your at idle your alt is putting out less then what is required to run all of your lights, ACC;s and lifting your plow, a 2nd batt will help your lights to stay bright and lessen the load put on the single batt.

    There are more reasons but I'm running low on ink.
     
  13. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,926

    Mass, was saying to add a solenoid to the 2nd battery. My question was. What is adding a solenoid going to.Do? And why?
     
  14. calhoun

    calhoun Senior Member
    Messages: 165

    Adding a solonoid isolates the 2 when truck is not running. You can run one totally down and still have the other to start. See my comment above. It all depends on what use you need the 2nd battery for.
     
  15. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,926

    Still do not see the need in a plow application
     
  16. calhoun

    calhoun Senior Member
    Messages: 165

    No need to isolate if plowing is why you are installing the 2nd battery. The OP mentioned camper wiring. If camping is why he is installing a 2nd battery then this wiring, connected to an isolated battery, is a good way to go.
     
  17. Thank you....
     
  18. snowymassbowtie

    snowymassbowtie Member
    Messages: 75

    The solenoid is added to keep the batteries isolated from each other when the vehicle is not running. When the vehicle is off the 2 batteries try to equal out,meaning the bad will suck life from the good. So if you do wire them direct thats what happens and also why if you do go direct they should be the same age,size etc.. This was how we wired ambulances, as well an option we offered to plow trucks and any other type of vehicles we wired. If you have 2 identical (or close as possible) batteries you dont need it. But like Calhoun said it will work as a back up if your primary was dead.
     
  19. Cosmic Charlie

    Cosmic Charlie Senior Member
    Messages: 228

    I just noticed that on the new 2015 2500 HD's there is NO option for ordering DUAL batteries (?) like my 2011 has ...
     
  20. cat320

    cat320 2000 Club Member
    Messages: 2,223

    the option is there it will cost you $135 730 CCA