Charging Battery with Alternator - Warning

Electrical and Ignition

  1. Mattax

    Mattax Just the facts, ma'am FABO Gold Member

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    We've discussed this here more than a few times. Usually about how easy it can be to cook the battery or overloading the charge wiring. Here's another reason. "Any attempt to charge a low battery by the alternator will result in stator windings burning out"
    s-l1600.jpg
    ebay item # 222689173585 This is an old reman by The Remanufactured Motor parts company. Box says 1973.
    p/n is RO 291167 but haven't found a cross ref yet to 'rating' or Chrysler number.
     
    Last edited: Dec 23, 2018
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    • 67Dart273

      67Dart273 Well-Known Member

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      Yup, a failing in general design WHICH CONTINUES WITH AT LEAST SOME VEHICLES CURRENTLY
       
    • Dana67Dart

      Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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      So if you leave your lights on in a parking lot and comeback to find a dead battery you are supposed to use someone else's alternator to recharge your battery and cook theirs?????
       
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      • Mattax

        Mattax Just the facts, ma'am FABO Gold Member

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        laugh2-gif.gif Yes, well kind of. laugh2-gif.gif
        My guess, based on the location of the tag and the first sentance is they were most concerned with someone who had really run the battery way down.
        A few hours in the parking lot is bad, cause its too low to turn over the engine, but maybe not as the worst cases.
        Not that I would have ever done such a thing. :rolleyes:

        OK. So I did, and we had no charger even back at our base and that was a good 20 minute drive away. After getting the jump start, I had to baby the throttle to keep the charge rate down. I coasted where ever possible in neutral, kept in in 3rd and lowest rpms as possible. It would take hardly any effort for the charge rate to go over 20 amps. Turning the lights on helped keep some load off the charge circuit as long as I could keep the rpms down. But it also meant more load on the stator. So I wasn't helping the alternator by doing that. However the battery and the charge wires were my big concern, and for good reason.

        It may be entirely coincidental that a year later that alternator gave out. It happens that today I was checking through my stack of alternators to see what was wrong with them. I assumed the one mentioned above had a bad diode. It turns out one of the stator leads showed an open winding. Hmmm. confused-gif.gif Maybe just a cheap rewinding or replacement stator but maybe not the whole story.

        That's how I stumbled across that e-bay ad. I was looking for photos of 37 to 60 amp squarebacks. The parts book shows 65 amp units had a different housing and I wanted to verify which one mine is if I could.
         
        Last edited: Dec 23, 2018
      • 67Dart273

        67Dart273 Well-Known Member

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        ............Battery charger.......... The idea is heat and duty cycle. If you can "get a jump" and get going and a short trip home, you are likely OK, but I would not run it for hours to charge it up

        When I bought my 70 V code, I didn't know that. The owner, a friend, had bought a new VeeDub camper van, and the dealer in Sacramento insisted on holding the Roadrunner for collateral. Some parking lot jock ran it clear down dead and left it that way ---left the 4X flashers on. FOR A MONTH. I flew up to get it, on a side note, my baggage on a PSA flight from San Diego to Sac was a small overnight bag, and a spare tire tied up in cardboard!! LOL

        When we first jumped and started it up, the battery was so dead that the alternator would not "self excite." We had to let it run for a few minutes before it would "pick up" and charge.

        Nevertheless, I jumped in and drove it hours and hours south.........to NAS Miramar. It was all downhill from there LOL

        Before I owned it, when it was new. He and I had been to Lions, where he'd trophied in pure stock

        attachment-jpg.jpg

        Me about 71--73. I was an ET in the Navy at Miramar, ETR-2, I fixed GCA RADAR and TACAN. The reason there are no longer "dust trails" on the sides is that some young chick had a-holed the car down in National City, and "limelight and all" told the cop "I just didn't see him!!!" The girls were window shopping, I was stopped for a light in traffic

        attachment-jpg.jpg

        This poor old faded photo from a 35mm slide is either 73 or 74. By this time I had swapped a 340 into it, and THAT was a lot of fun!! You might notice it has "funny lookin" turn signals up above the bumper in the grille. That's because I had aircraft landing lights in the bumper. I got a ticket for them earlier in CA, had them mounted in the high beams Got caught in an infamous CA roadside emissions trap

        81sruds-jpg.jpg

        Incidently, you hear some of us on here talking about damaged ammeters and bulkhead connectors. Both the original owner and I were amateur radio ops then as now (George still has his ORIGINAL callsign!!) and that car "ate" the bulkhead connector back then. I drilled it out and ran larger gauge wireing through there. Obviously before Al Gore invented the internet!!!
         
        Last edited: Dec 23, 2018
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        • Tooljunkie

          Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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          Alternators arent battery chargers.
          Running lights on a dead battery just increases the load.
          Fans of accessories off. And drive it like you always do.
          But get it on charge as soon as possible.
          A trickle charge is always better than a fast charge.
           
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          • Mattax

            Mattax Just the facts, ma'am FABO Gold Member

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            I agree TJ, but there was no choice. Even with the lights on occasionally and rpms down the whole trip, the battery was super hot in 25 minutes or so and took hours to cool. Next morning it was cool and would take additional charging. It would have been much much much better to have had a charger running at 2 amps or less.
             
          • Bodyperson

            Bodyperson A little sketchy

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            Leave the jump vehicle hooked up as long as you can.
             
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            • Tooljunkie

              Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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              Have had to do it myself,but i dont make a habit of it.

              Had a crew that would work with the truck radio playing,and run it dead constantly.
              It was equipped with an isolator and a second battery for a winch.
              So they would use it to boost.
              Smoked alternator and burned up several isolators. Finally the cause came out in a discussion,put an end to misssd diagnosis and comebacks.
               
            • robert flippo

              robert flippo Well-Known Member

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              Maybe i am missing something here, but what is the purpose of a voltage regulator, i thought once the battery was at full charge, and by driving 5 to 10 minutes the regulator steps down how fast the charge is according to the number of things like lights and wipers, if your alternator continued to charge at the same rate any time you started your car, if the regulator don't drop the voltage to the battery, it wouldn't matter if you had a weak battery or not,your battery would explode
               
            • Mattax

              Mattax Just the facts, ma'am FABO Gold Member

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              I'll give this a shot.
              The regulator
              tries to maintain the system at approximately 14 Volts.
              it controls power going into the alternator's rotor. It's spinning electro-magnet. More current into the electromagnetic, the stronger the magnetic field.

              The battery
              draws current when recharging just like devices such as a lights or electric motors.
              The voltage across the light or battery determines how much current it will draw.
              For example, headlights at 14 volts will draw around 10 amps. If they are supplied power at 17 Volts, they might draw over 15 amps (in which case the circuit breaker will trip or the lights will burn out quick).
              A battery is different because its draw varies with its charge state.
              example 1:
              A battery that has just started a car may initially draw 10 to 20 amps when supplied at 14 volts.
              After a minute or so, it will draw 5 amps at the same 14 volts.
              Within 5 minutes, it will be drawing less than an amp.
              Continually subject to 14 Volts, eventually a wet cell car battery reaches an equilibrium where the chemical reaction essentially stops. It has a surface charge of around 13.2 volts, but really only has stored energy at 12.8 Volts. Lots of stored energy. Enough to turn the starter motor and then some.

              example 2:
              A battery that is fully discharged will draw more than 20 amps when supplied at 14 Volts.
              The current must be limited if we don't want it drawing 40 amps.
              Reducing the voltage is how its usually done.
              Some chargers do this automatically, or we can do this manually by setting the charger to a lower rate.

              When there is no charger available, we can take advantage of the limits of the alternator design to reduce current to the battery.
              An alternator's capacity to produce power goes up with rpm.
              If the alternator speed can be kept down, many alternators simply can not supply 40 plus amps at 14 Volts when the engine speed is under 1000 rpm.
               
              Last edited: Dec 24, 2018
            • Tooljunkie

              Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

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              It regulates voltage. Generally speaking, 14.2 to 14.6 volts. Thats all it does.
              Low voltage battery discharges,high voltage and it damages battery and electrical systems. The alternator matches the demand.
               
            • Mattax

              Mattax Just the facts, ma'am FABO Gold Member

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              This is a moderately discharged battery hooked up to charger.

              (1) Charger attached and dialed to bring voltage across battery to 14.2 Volts. Current draw was around 35 amps.
              upload_2018-12-24_11-37-33.png upload_2018-12-24_11-37-58.png

              (2) As current did not drop after a couple of minutes, I manually turned the charger down to get 13.3 volts, 8-10 amps

              upload_2018-12-24_11-40-35.png upload_2018-12-24_11-41-26.png

              (3)45 minutes later voltage has come up to 14.4 V, yet the charge rate is down to 5 amps. thumbs_up-gif.gif
              upload_2018-12-24_11-42-49.png upload_2018-12-24_11-43-45.png
              When that battery charger was new it had a temperature probe to place in a battery cell. It would have automatically reduced the power if the acid started to get too warm.
               
              Last edited: Dec 24, 2018
            • Mattax

              Mattax Just the facts, ma'am FABO Gold Member

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              TJ makes some good points.
              Power comes from either the battery or the alternator; whichever has the higher voltage.
              The amount of power supplied equals the demand.
               
            • Dave NEO

              Dave NEO Well-Known Member

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              they rarely get that dead to cause problems for charging system after you get jumped and started - if you are old enough, you know you've done it and seen it a thousand times with no probs..
               
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              • Dave NEO

                Dave NEO Well-Known Member

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                now was that because you ran a pretty good kicker behind that CB ----c'mon...tell the truth... lol. (yes I still have my call sign and skipshootin' pirate radio license!)
                 
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