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charging a battery

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  • charging a battery

    If the car sits too long, and the battery needs charging, what is the consensus on technique? Do you leave the battery and cables in place and attach the charging cables and charge away? Disconnect the cables from the battery and charge it in the car? Remove it from the car to charge?
    I know it sounds like a lame question, and for my other cars I have charged leaving everything intact with no repercussions, but I hesitate to do something that will fry these seemingly fragile ecu's. The owners manual is somewhat contradictory in it's instructions, and a search here reveals people reporting having ecu problems after simply disconnecting their battery.
    So, just checking what others do.

  • #2
    I leave it in on a 2 amp charge

    81 Ur Quattro
    87 911 M491 Cab
    89 M3
    89 944 T

    What can I say,
    I love wide fenders!


    • #3
      I have just hooked up the charger while in the car and connected. No issues.



      • #4
        I use the BMW plug-in through the console lighter. Trickle charging, works good. Just leave in place. No problems.

        BMW CCA San Diego Chapter #192742
        '90 M3 AWII - Garage Queen
        '09 540i Touring 6 Spd - Son's DD
        '03 530i 5 Spd - SO's DD
        '03 Nissan Frontier Crew Cab - My DD & Range truck
        '05 330i ZHP 6 Spd - Alternate DD
        '15 Honda Pilot - Daughter's & Grandkids Hauler


        • #5
          Jump start it and take it for a nice long ride. That's what I do after winter hibernation.

          Before you leave the driveway put a voltmeter across the terminals and make sure you are making at least 13.5 volts while the car is running to ensure the alt is working correctly.


          • #6
            I use a trickle charger and leave everything connected.

            Schwarz 1990 Sport Evolution


            • #7
              leave it in charge on 10 amps for an hour then 2 amps until the charger says its charged


              • #8
                I pull the battery to clean the tray, inner fender area, baking soda the area, and the clean terms. Clip on my Craftsman charger and let her soak it up for a few hours on 10 amps, then cut it down to two amps for a few more hours. I wish I had bought a charger with a peak detector and auto trickle function. I don't have a sealed-spiral cell battery, those might need different care.