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Just added dual batteries... have some questions

Discussion in 'Chevy Trucks' started by obrut, Nov 29, 2007.

  1. obrut

    obrut Senior Member
    from IL
    Messages: 149

    I added the second battery tray to my 2000 NBS GMC truck. Bought the battery tray from the dealer for $25 and a friend gave me 2 gauge welding wire. I crimped the ends on the wire and wired the truck up. I ran the 2 gauge wire from the aux battery to the main battery and put the studs on the main battery. The negative side of the main battery has the vehicle, plow and aux negative wire on it and the positive side has the vehicle, plow and aux battery too. When I went to start it I noticed that the speedometer needle was all the way at 100mph. I disconnected the positive wire from the main battery and then connected it again and it was fine. Not sure what happened there, anyone have any ideas? I also have a 1.5 year old a/c delco battery in the truck. It is a 1000 amp 850 cold cranking amps. So I bought another one just like it and put in the aux spot. I did a search and a lot of people say to buy two new batteries, but why? The 1.5 year old battery has had an easy life of just powering the truck with no other add ons. This is the first year that I put the plow on this truck. What are the negative effects of having the same batteries with one being a little older?

    BTW it made a huge difference when I hooked the plow up, for anyone thinking about the dual batteries, go for it.
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Not at all uncommon.. the instrument clusters sometimes have to "relearn" their needle positions after disconnecting the battery .....

    It would have fixed itself if you would have driven it down the road and it's nothing to worry about.
  3. Burkartsplow

    Burkartsplow PlowSite Veteran
    Messages: 3,246

    Duals is the way to go, if your running plow, salter, lights, radio all night long, you need the extra juice. Pretty simple hook up also. well good luck this year.
  4. Philbilly2

    Philbilly2 PlowSite Veteran
    Messages: 3,770

    the reason that I have heard people change batterys in pairs is because the wear on the old battery verses a new one causes the batterys to transfer power back and forth when the truck is not running, which in turn, wears both batterys out. I don't know if it is true, I just always replace my batterys in pairs, and my 3rd battery I only plug in while plowing, and I unplug when the truck is not running.
  5. ahoron

    ahoron Senior Member
    from here
    Messages: 422

    I spoke to a distributer for a large battery distributer. He said he has never heard of one new battery destroying the older battery. I believe him since he is in the business of selling batteries. He would, in my opinion, be an expert. Why would he say that if it's not true?
  6. Mark Witcher

    Mark Witcher Senior Member
    Messages: 605

    Maybe your battery expert just doesnt know.Its the same as dry cell batteries in any hand held device, always replace with all new. dont mix half worn and new. I suggest you talk to the trucking companies as to how to replace batteries hooked together.A one year old battery would be considered still new.
  7. traviswalker007

    traviswalker007 Senior Member
    Messages: 188

    97 F250 Hd

    Can someone tell me how to run a dual battery set-up for this vehicle. My 03 3500 dump has dual batterys but has a isolation module coming of the alternator and i noticed on this thread that the batterys were hooked up together?? if thats true then how do u charge the second battery with out overcharging the first??
  8. Philbilly2

    Philbilly2 PlowSite Veteran
    Messages: 3,770

    Just run Positive to Positive. It will act like a set of jumper cables if you were jumping the truck. It will make the two batteries have the same power levels in both. No overcharging, just equal.
  9. Bill 211

    Bill 211 Member
    Messages: 40

    an isolator is good if you dont want to drain the 2nd battery while the truck isnt running
    like if you had to park & leave your strobe lights on for a while
    it keeps the main battery from getting drained down , thus the truck will start, even if the second battery is weak