Battery Question

Discussion in 'GM Electrical Tech' started by Salesguy1980, Jan 4, 2013.

  1. Salesguy1980

    Salesguy1980 Rockstar 100 Posts

    Hello All and Happy New Year!

    I went to start my truck today. Hit my remote start and usually I hear my truck, can wake the dead with it. Nothing. I head outside and I can open the doors and lights go on but dead battery, won't turn over. I jumped it with my wife's Envoy and its fine now. I am in sales and do sit in my truck a lot and fire up the macbook for work and stuff. Some times I keep it running some times I don't. I do charge my iPhone, macbook and blue tooth daily, not at all the same time and macbook only when driving.

    My truck is a 2011 GMC 2500HD Crew 6.0 and has 47K on it. I have the original factory battery. I do have a spot for a 2nd battery and wanted to know the best way to hook it up. I will likely buy 2 new batteries (Interstate or Optima), just not sure how to wire it. Ideally in series I'm thinking to give a longer time to drain. I do not want to have to pop the hood and connect the 2nd battery as a jumper. Just looking to have more power for the gadgets I use daily. Not even sure if its factory wired for a 2nd battery. I do have the snowplow prep package with bigger alternator.

    Any and all ideas and schematics would be helpful and appreciated. I can do most work on my vehicles just not the most comfortable with electrical.

    Thanks in advance

  2. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    ***Moved to Electrical Tech Subforum***

    - - - Updated - - -

    I am sure someone will come along with your answer soon. There are many members here running dual batteries. I believe that you would want to run an isolator on the second battery so if you kill your main battery you still have the second battery to start the truck. I know that [MENTION=50075]SurrealOne[/MENTION] is running dual batteries and is very well versed in electrical mods. Maybe he can shed some light on the subject.
  3. Jamm3r

    Jamm3r Member 2 Years 100 Posts

    I just did this and will post some photos although my truck is a little older so the details may differ a little. What I have done is move the stock battery to the new battery tray installed in front of the firewall over the right fender, and then installed a Group 24 deep cycle battery in the stock location. On my truck a group 24 will not fit in the firewall/right fender location hence the move. You would have to measure to be sure, group 24 is a couple inches higher than the stock group 78.

    They worked fine in parallel but I've put in an isolator to allow the aux battery to be fully discharged without affecting the ability to start the engine. For me it's all for a travel trailer so the aux battery is wired to the trailer circuit, the main battery runs everything in the truck. There are plenty of other ways to do it but simple is good so I'd suggest wiring them in parallel with heavy cable and if that isn't satisfactory then explore other more complicated alternatives.

    In general Chevy doesn't put in battery cables for a second battery unless the second battery is being installed as a factory option.
  4. SurrealOne

    SurrealOne Former Member ROTM Winner 1000 Posts

    If all you want to do is increase your runtime and you don't care about protecting yourself from draining the system dry, series is the way to go. [MENTION=52280]nakranij[/MENTION] is running dual batteries in this fashion. Perhaps he'll share the schematics he used and provide you with some photos. (My dual isolated setup is probably overkill for your needs, as my system is designed to withstand 300amp draws from my winch.)
  5. PantheraUncia

    PantheraUncia Epic Member 5+ Years 1000 Posts

    I had one in visio somewhere, no clue where it is now, but I can recreate it when I get home from work and take some pic's.

    I still haven't found the Battery terminals I want, but it works really well and I haven't had any issues.

    I will post info later tonight depending on when I get home.
  6. Jamm3r

    Jamm3r Member 2 Years 100 Posts

    Having problems uploading images, server says they're too large, not sure what the problem is.

    Anyway here's what I can upload.

    This is the new battery location before removing the braces and replacing them with the tray:

    And here is the stock battery location with the stock group 78 battery removed and replaced with a group 24 deep cycle:

    The connection between them is through a simple continuous duty contactor I got at the NAPA:
  7. PantheraUncia

    PantheraUncia Epic Member 5+ Years 1000 Posts

    This is a diagram I wish I had when I started my dual battery install and this is how mine is setup:


    My truck did not come with the second battery tray on the passenger side, so I had to buy it, but the GM one is cheap, so I got it from the stealership.

    You have to make absolutely sure that the specs of both batteries are identical, so I went with 2 brand new optima's (you don't have to use optima). But the cold cranking amps, amps, etc need to be the same so that they charge evenly.

    2 different batteries of different spec are not recommended from what I had read. At bare minimum you want to use 4ga battery cable. Between my batteries, that is what I am using, but I would like to use a heavier cable later on, but that is a different story for another time.

    You will also need to (as a safety precaution) Fuse the positive battery cable at both ends, no more than 12 inches from each battery. I went with 80 amp fuses, but may move to 150 or 250 amp fuses later when I have more stuff in the truck with a bigger draw.

    I am not using an isolator in my setup, because at the moment, my I am not drawing enough to worried about both batteries going dead from pulling to much power. The isolator is another safety precaution as if you leave a power inverter turned on, it will drain both batteries, it will just take longer :). In my case, the laptop is only charging when the truck is running or for periods less than 30 minutes or so. The after market stereo I have hasn't drained both batteries even after a few hours of being on.

    Your wench is going to pull some amps, so you might want to go with larger fuses. I will let @SurrealOne chime in with anything I missed.....
    Last edited: Jan 5, 2013
  8. SurrealOne

    SurrealOne Former Member ROTM Winner 1000 Posts

    I seem to recall you replaced the 4ga cables between your batteries with 1/0AWG cables?

    I don't believe he's running a winch.

    Nothing else to add...
  9. PantheraUncia

    PantheraUncia Epic Member 5+ Years 1000 Posts

    I guess I need to "clarify". My "big 3" cables (Alternator to battery, Battery to engine ground, and Battery to Chassis ground) are upgraded to 1/0 aut cables with help from Surreal as he had done the upgrade before. If I were to buy another truck soon (new or used) that would be the first upgrade I would do, along with the second battery.

    The cables between my 2 batteries are 4ga. from an extra amplifier kit I had in the garage. I am thinking about upgrading those cables to 1/0 aut as well, however that project is on permanent hold pending the outcome of some other issues with the truck I am in the process of determining a course of action on.
  10. PantheraUncia

    PantheraUncia Epic Member 5+ Years 1000 Posts

    I was able to take some pics of my dual setup and make notes on each pic, so here is how my setup looks:

    (This should cover "most" 1999-2002 GM Trucks with the 5.3L or 6.0L Gas engine. I would assume that the 4.xL and the 6.6L Dmax would also be similar with the obvious differences)

    1. Overview. (Basic 2 battery setup)


    2. Driver side/ Primary Battery (2000 Model Year)

    The only item I have not marked here is the Engine Ground. The engine ground is a 1/0 Aut cable connected to the (-) side post of the battery. You can see the Chassis ground on the top (-) post of the primary battery above.

    • [*=1]The 1/0 Aut cable(Red (+)) on the battery is coming from the Alternator. The 4ga.(Red(+)) cable is going to the second battery.
      [*=1]The 1/0 Aut (Black(-)) on the battery is going to the engine ground and chassis ground. The 4ga. (Red(+)) is going to the (-) on the second battery (I did not have black 4ga cable available).
      [*=1]There is an 80 amp fuse 12 inches from the primary battery on the (+) cable.

    3.Passenger side/ Secondary Battery (2000 Model Year)


    • [*=1]The 4ga.(Red(+)) cable is coming from the primary battery.
      [*=1]The 4ga. (Red(+)) is going to the (-) on the primary battery (I did not have black 4ga cable available).
      [*=1]There is an 80 amp fuse 12 inches from the secondary battery on the (+) cable.
      [*=1]There is a 4ga. Ground going from the (-) to the ground post.

    4. Alternator Cable upgrade.

    I included this photo show the poor quality of the factory cable compared to the custom one that was created. The factory cable might be "sufficient" but that is about all it is.

    The "big 3" cables were upgraded to 1/0 Aut:

    • [*=1]Alternator to battery
      [*=1]Battery to engine ground
      [*=1]Battery to chassis ground

    Future cable upgrades:

    • [*=1]Primary to secondary battery (+) from 4ga. to 1/0 Aut
      [*=1]Primary to secondary battery (-) from 4ga. to 1/0 Aut
      [*=1]Secondary ground from 4ga. to 1/0 Aut

    Other Electrical upgrades in the future (Pending my truck does not end up in a junk yard)

    • Alternator upgrade from 105 amp (stock) to 200-300amp High Output.
    • Battery terminals with voltage meter built in so I can see how many Volts is coming out of the batteries.
    Last edited: Jan 7, 2013
    Chesters likes this.

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