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  1. #1
    Join Date
    Jul 2012
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    usa ca
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    Default how to charge batteries?

    We have a 2002 gmc 2500 duramax. Went to start the truck and it is completely dead. I have a charger but no idea how to hook it up. Hubby is deployed and usually does it. I know how to hook up to a battery but wasn't sure if this was different being diesel and having two batteries. Help please?

    Thanks!

  2. #2
    Join Date
    Apr 2001
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    CA
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    Arrow

    Welcome aboard!

    Battery charging (or jump starting) is no more complicated with 2 batteries than one. There should be a red plastic box (size of a deck of cards) on the left side of the engine, near the top. Pop it open and there'll be a large stud/nut inside. Clamp the Positive there. Above the box should be a silver metal tab, approximately 1" x 3". That's for the ground. If you don't get good contact (sometimes they just don't), I suggest grounding on the rear A/C compressor boss (just inboard from the "box", where the A/C compressor bolt passes through). If that isn't simple enough to figure out, you can charge/jump directly from either battery. They are wired parallel, so + and - on either battery is the same for both. The passenger side battery is a little further to reach, but the terminals are easier to access, with fewer obstacles. WATCH for the fuel lines, etc. when connecting the + clamp there. Make sure you don't short to ground, or it can burn right through the metal lines. Make your + connection first, ensure it's clear, and it should be OK. If the terminal caps are still on the batteries, they just pop off.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  3. #3
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    Location
    usa ca
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    Default

    Thanks. How do I make sure not to short to ground? I"m not exactly sure what that means.
    If I'm reading right, it's like hooking up jumper cables? I've done that before.

    Thanks, again!

  4. #4
    Join Date
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    It's just like hooking up jumper cables, except there's a box on the other end instead of another vehicle.

    "Short to ground" (short circuit) merely means contacting a grounded component with the Positive cable you are connecting. This is only a factor if there's power to the Positive connector, and the other clamp (ground, often the black cable/clamp) is connected to the vehicle ground (frame, negative battery terminal, engine, or other "grounded" part). It causes an arc, like a welder, and will burn or melt metal if there's enough current (like an automotive battery).
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  5. #5
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    Jul 2012
    Location
    usa ca
    Posts
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    Default

    I get it. I just need to make sure the neg end doesn't touch any other part of the truck once i've hooked up pos end.


    Thanks a ton!!!

  6. #6
    Join Date
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    Arrow

    Quote Originally Posted by 5abelsons View Post
    I get it. I just need to make sure the neg end doesn't touch any other part of the truck once i've hooked up pos end.


    Thanks a ton!!!
    Um...No.

    Make sure the Negative end doesn't touch any part of the truck UNTIL AFTER the positive is connected. Red/Positive clamp to Battery Positive. Once that is connected, Black/Negative clamp to truck ground (any large bolt on the frame or engine is usually good). If both aren't connected, positive to positive, and negative to negative, no charging (or jumpstart) will occur. Connecting the Positive first helps prevent a short circuit.

    Place the charger on an insulated surface away from the truck (not touching the truck), like on a box, stool, or milk crate.

    AFTER the cables are connected, THEN connect the AC (house) power to the charger, make sure it is selected to 12V (if it has a selection). You may also have to select a charge rate. 10 amps will normally charge both batteries overnight (about 12 hours). 40-50 amps should fully charge in 2-4 hours. I recommend the slower charge, unless you must drive sooner. In either case, leave the hood up to prevent gas buildup (batteries vent gas when charging, and can be explosive if enclosed). This is also why we don't (normally) make both connections to the battery terminals, as this can cause sparks too close to the battery. If you "fast charge", watch it closely. If the charger has a "meter", the needle should normally start high, and lower as charging continues. If you are connected to "dead" batteries and get no needle movement (once connected, properly selected and powered), you have a bad connection or the batteries are bad. If the vents bubble liquid or vapor, leak or do anything that doesn't seem "normal" (like get very hot, enough to soften plastic or clamp insulators/wires), STOP the charging (exact reverse order). You probably have bad batteries, and it needs to be checked before trying to charge. A "wet" spot around the terminal connectors normally means the battery is leaking (bad), and need to be replaced.

    I'll be here for a while. Just holler if you need more help (or confusion).
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

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