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    1. #1
      Join Date
      Nov 2012
      Location
      ocala fl
      Posts
      302
      Country Flag: United States

      car charging at 13.2

      I have an optima battery that is about 4 years old. I usually charge at about 14.8 V. Today it started charging at bout 13.2. My gauges are Dakota Digital analog/digital . I checked the system with my 30? year old Snap On digital tester. All 4 lites didn't come on so alternator is good. I then put the battery on a regular charger and in less than a half an hour at 10 amp it was charged. I then switched it over to 2 amp and in about half an hour it was charged. Still charging at 13.2 V. Took it up to Auto Zone and had them check it. He said the regulator was bad. But the battery was good at 12.4 V. I then took it to Advance Auto Parts and had them check it. Everything including the alternator was good. But the battery was also at 12.42C. Voltage went down to 11.35 cranking. Charging system at no load was 13.39 and loaded at 13.0. What gives. I have always considered a battery at 12.4 as discharged or bad.Tomorrow I'm going to pull the alternator and take it down to have it checked. It is a 100 Amp and I have to call Vintage Ait to find out whom made it



    2. #2
      Join Date
      Dec 2010
      Location
      Fredericksburg, VA.
      Posts
      3,155
      Country Flag: United States
      You did not specify what car or alternator you have but based on your description of a reduced charge rate, I would suspect a bad diode in the alternator. If you have a GM 10SI or 12SI a replacement diode trio can be purchased for around $12-$15 from any auto parts store and replacing it is a simple 10 minute job. I would also recommend you read through some of the tech articles on Mad Electrical for some great background information on charging systems.

      http://madelectrical.com/electrical-tech.shtml
      Steve Hayes
      "Dust Off"
      68 Camaro

      Given sufficient initial acceleration, even pigs can fly!

    3. #3
      Join Date
      Nov 2012
      Location
      ocala fl
      Posts
      302
      Country Flag: United States
      I'm not sure what alternator it is and who manufactured it. It is a GM alternator of later design. It came with the Vintage Air front runner system. It is in a 66 Lemans conv with BBC. I have had it for 4/5 years. It is the battery voltage that kills me. I'm use to a 14.8 to 15.2 charging and a 13.6 battery voltage. Is this normal for a optima battery? Darn new technology!
      ....................................lost in the 60's .......................................

    4. #4
      Join Date
      Dec 2010
      Location
      Fredericksburg, VA.
      Posts
      3,155
      Country Flag: United States
      Your problem has nothing to do with the battery, IMO. The scenario you describe is typical of a popped diode in the alternator. As you stated in your first post remove the alt and have it tested off the car. It will likely generate voltage but I suspect it will fail a load test.
      Steve Hayes
      "Dust Off"
      68 Camaro

      Given sufficient initial acceleration, even pigs can fly!

    5. #5
      Join Date
      Jul 2016
      Posts
      341
      Country Flag: United States
      Def sounds like an alternator problem. I thought the front runner set-ups used 140 amp alternators ??

    6. #6
      Join Date
      Sep 2010
      Location
      Beach Park IL
      Posts
      2,838
      Country Flag: United States
      It's a 1 wire CS130 manufactured by TuffStuff. Make sure your alternator has a good ground path back to the battery. If that is all good, replace/rebuild the alternator.
      Donny

      Support your local hot rod shop!

    7. #7
      Join Date
      Nov 2012
      Location
      ocala fl
      Posts
      302
      Country Flag: United States
      It is about 5/6 years old and I had TUFF STUFF rewire it to a 3 wire a couple of years ago. I got out my receipts last nite cause I need to know. That is why it is a 100/105? amp alternator. No one has given me an answer about the optima battery which only charged to about 12.4 V on my charger. Should it not be 13.6. I tried to call optima batteries this afternoon. 21 times and it was busy! Never did get thru!

    8. #8
      Join Date
      Jan 2006
      Posts
      385
      Country Flag: United States
      My optima red top measures out to be between 11.5 and 12v with the car off. But I never have any problems with it (have had it for about 3-4 years now). I charge at 14.2-14.5V with a 105 amp GM CS-130 alternator off a 1990 Camaro.
      1971 Camaro
      GM HT383, MiniRam EFI, AFR heads
      "8-speed" trans (700R4 + Gear Vendors OD)

    9. #9
      Join Date
      Nov 2006
      Location
      Mountain Springs, Texas
      Posts
      4,488
      Country Flag: United States
      What kind of charger are you using? optima needs a special charger. I use Odyssey batteries and had to buy their 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

    10. #10
      Join Date
      Jan 2006
      Posts
      385
      Country Flag: United States
      I don't use a charger. The alternator keeps it charged and it'll retain that charge on its own. I sometimes don't drive the car for a few weeks and it'll start right up.

      I measured the current draw with the car off and it pulls about 25 mA... radio, keyless ignition RF TX/RX, ECM, etc...
      1971 Camaro
      GM HT383, MiniRam EFI, AFR heads
      "8-speed" trans (700R4 + Gear Vendors OD)

    11. #11
      Join Date
      Nov 2011
      Location
      Wylie, Texas
      Posts
      279
      Country Flag: United States
      I use a Deltran battery tender on my red top that charges at about 13V. Without the charger the battery will eventually drop down to about 12v. The alternator will charge around 14V.

    12. #12
      Join Date
      Jan 2006
      Posts
      385
      Country Flag: United States
      I don't get it... you guys are saying that 12v is a bad thing in terms of the battery output?
      1971 Camaro
      GM HT383, MiniRam EFI, AFR heads
      "8-speed" trans (700R4 + Gear Vendors OD)

    13. #13
      Join Date
      Nov 2011
      Location
      Wylie, Texas
      Posts
      279
      Country Flag: United States
      I didn't say that. 12v is normal when not charging.

    14. #14
      Join Date
      Nov 2012
      Location
      ocala fl
      Posts
      302
      Country Flag: United States
      I took the alternator down to a local alternator repair shop and had it checked out. It was putting out 14.8 V and well over 100 amps. I'm going to try another battery and see what happens. I called optima today and talked to tech. The guy I talked to could not give me any type of an answer. I asked him what the voltage reading was on a new Optima battery. He had to look it up! You would think that they would know that. It appears that a new red top is 13.6 to 15? something.

    15. #15
      Join Date
      Jul 2016
      Posts
      341
      Country Flag: United States
      Quote Originally Posted by chpr1972 View Post
      I took the alternator down to a local alternator repair shop and had it checked out. It was putting out 14.8 V and well over 100 amps. I'm going to try another battery and see what happens. I called optima today and talked to tech. The guy I talked to could not give me any type of an answer. I asked him what the voltage reading was on a new Optima battery. He had to look it up! You would think that they would know that. It appears that a new red top is 13.6 to 15? something.
      What actually prompted you to investigate the battery and or alternator ??? Are you having trouble starting because of a weak battery ???? You just checked the voltage because you wanted too ?? If your not having any staring issues you may just be fine. Just a thought.

    16. #16
      Join Date
      Jan 2006
      Posts
      385
      Country Flag: United States
      Also make sure the sense wire is showing the right voltage at the alternator.
      1971 Camaro
      GM HT383, MiniRam EFI, AFR heads
      "8-speed" trans (700R4 + Gear Vendors OD)

    17. #17
      Join Date
      Nov 2012
      Location
      ocala fl
      Posts
      302
      Country Flag: United States
      what happened was the car usually charges at 14.8. Last time I took the car out, it was charging at 13.2. As an older than dirt person, if a battery did not show 13.6v it was bad or discharged. But this battery was at 12.4V and had 900 cranking amps out of a 800 rated battery, I wanted to know how that happened. When I get it back together with a different battery I will check the sense wire if I still have a problem.

    18. #18
      Join Date
      Jul 2016
      Posts
      341
      Country Flag: United States
      Quote Originally Posted by chpr1972 View Post
      what happened was the car usually charges at 14.8. Last time I took the car out, it was charging at 13.2. As an older than dirt person, if a battery did not show 13.6v it was bad or discharged. But this battery was at 12.4V and had 900 cranking amps out of a 800 rated battery, I wanted to know how that happened. When I get it back together with a different battery I will check the sense wire if I still have a problem.
      Your Dakota Digital dash gauge was showing 13.2 I take it ?? Hmmm....

    19. #19
      Join Date
      May 2019
      Location
      Pensacola,Fl.
      Posts
      27
      I have always considered a battery at 12.4 as discharged or bad.
      No......a settled 12v battery will have 2.1V per cell...IE: read 12.6. This is when the surface charge has worn off.

      The regulator in your alt. is the control device that regulates the alt. It should be 13.8 to 14.2V

      Do a Voltmeter test direct to the battery.

      Crank the motor.....turn on the headlights ....turn on the heater blower motor.....bring the RPM to 2000 and test battery voltage.

    20. #20
      Join Date
      Aug 2008
      Location
      Charleston, SC
      Posts
      354
      See the next to the last entry on my thread on Dual AGM batteries. It has optima's required charging voltage that must be measured at the battery.

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