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Yes another dual battery thread - 03 Silverado 2500 HD

Discussion in 'Chevy Trucks' started by darryl g, Dec 30, 2015.

  1. darryl g

    darryl g Senior Member
    from CT
    Messages: 380

    Looking for some advice. Here's my situation. I have the HD alternator that came with the plow prep package but only a single battery setup. I run a Boss 8' Power V XT. I was only getting 3 years out of my lead/acid batteries so 2 years ago I talked to my battery dealer when replacing it (Interstate Battery) and they told me to go with an AGM battery. I got the MT7 $220 (715CCA/895CA). It recently failed after 2 years. It failed at a convenience store 1/4 mile from my auto mechanic so after unsuccessfully trying to jump me he installed an Exide 78C (630CCA/785CA) from his inventory - best he had in stock.

    Yesterday I finally got my battery dealer to run diagnostics on the AGM and they gave me a full replacement. He was actually confused. His tester passed it but it was obviously bulged and the voltage was too low. I've been buying all my batteries there for 15 years so he just gave me a new one. Note: It may have gotten drawn down due to a bad ignition switch in my truck which I just replaced. It was dead 2 different mornings. The ignition was really worn and acting funky and if you weren't careful could pull the key out and leave accessory on...had to do the wiggly/jiggly thing to start it and could pull the key out with it running...failure was imminent.

    So here are my options:

    1) Just install the new AGM and assume I just got a bad one. Obviously, it's the better battery but I've been told they do tend to have a higher catastrophic failure rate. For 2 seasons it handled the plow and my truck/trailer sitting on the side of the road with flashers on for an hour or 2 with no problems. Cab and headlight dimming was minimal when raising the plow compared to with the lead/acid batteries I had been running.

    2) Install a dual battery system. It's my understanding that because the batteries don't match, I would have problems if I just installed them in parallel with no isolator. What would happen is I just installed them in parallel with a new ground and a positive running to the other battery without an isolator?

    3) Just leave the lead/acid battery in and hold onto the AGM for when it inevitably fails. Can't see any good reason to do this other than just being lazy, lol.

    So what's the deal with these isolators? How does it know which battery is the auxiliary/accessory load one and which is the starting battery? Is it just what post on the isolator you connect them to? I wouldn't need to be connecting different loads to different batteries, right?

    For now I think I'm just going to install the new AGM battery and call the 2 week old lead/acid a spare. I like that the AGM has both the top and side posts so I can install the plow on the top post and not have a big stack of connections all on the side post...hard to get them all to contact properly.

    Thanks in advance.
  2. Philbilly2

    Philbilly2 2000 Club Member
    Messages: 2,129

    I would go with the dual battery setup. I don't believe in isolators on plow trucks. IMO

    If you have two batteries in parallel, your storage capacity is higher. When you plow is drawing amps, it puts severe strain on a battery. If you have two, the severe draw is lessened. Allows less amps to be drawn on one battery at a time. It is the hard amp pull that wrecks a battery fast. The voltage going up and down quickly is very hard on them.

    As for the battery that you choose, I am not a huge believer in AMG batteries, I ran them in some of my trucks years ago and was still replacing them almost as often as lead acid.

    Just made sure that if you do add a 2nd battery, you need to get another battery that is of the same life otherwise, they will swap the power back and forth until they both go dead.

    I am not sure that with the two batteries that you have there that you could not just install those two as they are both new. But someone who understands the difference better between a acid lead and an AMG needs to chime in on if they will compete with each other due to the different styles.
  3. mwalsh9152

    mwalsh9152 Senior Member
    Messages: 434

    I would go with a dual battery setup, but buy a new matching AGM battery. I run two Odyssey Group 65's with a higher amp alternator, cant remember how many amps.

    I've never had a problem with them in 6 years before yesterday. for the past 3 years the truck has only worked storms, nothing else. Batteries sat untouched until I would turn the key and fire it off 6-8 months later. I noticed one was weak this past week, and just ordered my replacements last night.
    Last edited: Dec 31, 2015
  4. darryl g

    darryl g Senior Member
    from CT
    Messages: 380

    Thanks for the replies. Not really interested in buying another AGM at $220 to match the one I have.

    I was originally going to put a dual battery setup in this truck when I bought it new, but told the dealer to stuff it when they quoted me $700 for the upgrade after quoting me $200 during negotiations. I wanted the cab lights and dual battery and they had a white one with the dual battery and a blue one with the cab lights. The salesman told me just pick he color you want and for $200 we'll upgrade either.
  5. SnoFarmer

    SnoFarmer PlowSite Fanatic
    from N,E. MN
    Messages: 7,921

    I have never found a dry/gell cell battery like a Odyssey that can hold up to the charge, discharge cycles of plowing.
    Even with a 2batt setup.
  6. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    This^^^^ Thumbs Up

    And this^^^^ Thumbs Up