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    Results 1 to 4 of 4
    1. #1
      Join Date
      Sep 2017
      Posts
      99

      Battery Voltage and LS3 Engines

      I have a 68 Chevelle with a LS3 cruise and connect kit installed. I’ve learned I have a battery draw somewhere so the battery basically dies. Voltage gets down to 9.5V and as a consequence the engine does not start. The last couple winters I’ve had a trickle charger on the battery and it keeps the battery around 12.5-12.9V. Car starts no problem. I bought a large battery charger a couple days ago to get the batter up from 9.5V back to 12.5. I measured the 12.5V with the charger connected. Disconnect the charger and voltage drops to 11.5. Charger says it charged. Car does not start at 11.5V. So my question is, are these LS3 engines that finicky that it needs 12.5V or am I missing something.

      Thanks in advance,
      Perry

      - - - Updated - - -

      Sorry, I forgot to say the battery I’m using is a optima yellow top

      perry

    2. #2
      Join Date
      Sep 2010
      Location
      Beach Park IL
      Posts
      2,838
      Country Flag: United States
      Sounds like your battery is junk. Put your trickle charger back on it and when it says fully charged take the battery to your local parts store and let them test it for you. When it fails, buy a new battery from them.
      Donny

      Support your local hot rod shop!

    3. #3
      Join Date
      Jul 2008
      Posts
      453
      Country Flag: United States
      Sounds like you have shoddy wiring causing a draw and the ECM is not getting the power it needs. LS ecms have voltage compensation maps in them to fire the injectors longer when the battery level is lower than nominal. As Donny says, your battery is probably gone. Are you measuring the voltage while cranking the car? That's the true test..
      *Jeff*
      Project Salty - 1964 4 door Malibu, beaten, neglected, red headed foster child
      Cammed LQ4 / T56 Swap Project Thread <-click to read! 😁

    4. #4
      Join Date
      Nov 2006
      Location
      Mountain Springs, Texas
      Posts
      4,488
      Country Flag: United States
      optima batteries don’t “like” conventional chargers in my experience. Use an optima charger on optima batteries.



      I have also learned to disconnect AGM batteries when charging them with an AGM charger.

      Don
      1969 Camaro - LSA 6L90E AME sub/IRS
      1957 Buick Estate Wagon
      1959 El Camino - Ironworks frame
      1956 Cameo - full C5 suspension/drivetrain
      1959 Apache Fleetside






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