Trouble charging battery | FerrariChat

Trouble charging battery

Discussion in '348/355' started by Carmellini, Sep 5, 2025.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. Carmellini

    Carmellini Formula 3

    Jul 16, 2019
    1,011
    Battery is dead. 97 5.2
    I have battery charger hooked up to positive and negative posts in engine bay. Charger reads out 6.3v
    and when I select 15A charge, the read out is 6v 100% charged? Why does my charger think it is
    a 6v system?
     
  2. andrejwolk1975

    andrejwolk1975 Karting

    Feb 28, 2020
    136
    Italy
    Full Name:
    Andrea M
    Half the plates badly sulfated or in shortcircuit? Half the plates, half the voltage.
     
  3. PaulK

    PaulK F1 Rookie
    Silver Subscribed

    Apr 24, 2004
    4,801
    Michigan
    Full Name:
    Paul
    How old is the battery?
     
  4. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    13,673
    San Carlos, CA
    Full Name:
    Mitchell Le
    No, the reason your battery charger thinks it is a 6V system is ...

    1) The charger is a microprocessor driven design to accommodate both 6V and 12V systems.
    2) It assumes that it is smarter than you and does not allow you to select which system.
    3) It sees 6V and it assumes that it is hooked up to maintain a 6V system and calls that 100% charge and ramps the charging current to nothing.
    4) It assumes that no one would be dumb enough to let the 12V battery dropped to below 6V before they call in a charger. Nevermind that it has nothing to do with being smart.

    To force it, fake it, be smarter than it and attach a 12V battery in parallel with your dead 12v-now-6v battery, and then attach the charger to that, and set it at 15A. Wait for an hour, and disconnect the 12V battery and let the charger charge up the bad battery to 13V.
     
    fboutlaw, Carmellini and Qavion like this.
  5. WATSON

    WATSON Two Time F1 World Champ
    Owner Rossa Subscribed

    Sep 9, 2010
    23,933
    WI
    Common problem in the Optima Red batteries I used to have.

    Your trick is how we saved them....it works.
     

Share This Page