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Starter Current Draw

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  • Electrical: Starter Current Draw

    What should the current to the starter on a 289 be during cranking? My engine always seems to crank a little slow, or maybe it just sounds that way. Anyway, I decided to check the current and it was about 350A during cranking. I have no idea if this is good, high or low.

    Any insights?

    Thanks
    Wayne
    Wayne
    "Trying to shed my CASO ways"

    sigpic

  • #2
    The spec I have from A.E.A. for an Avanti starter is 295 amps @ 4 volts delivering 6.2 ft/lb of torque with the starter locked (stalled) ; . Free running speed 5300 RPM drawing 50 amp @ 10 volts. I don't understand the 4 volts; that might be all the 12 volt battery is able to supply. I never tried it.
    Ron

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    • #3
      According to the guy that taught a basic electrical course to my fellow workers and I this week, around 200 amps is normal when cold. Amps rise as temperature rises.
      Jamie McLeod
      Hope Mills, NC

      1963 Lark "Ugly Betty"
      1958 Commander "Christine"
      1964 Wagonaire "Louise"
      1955 Commander Sedan
      1964 Champ
      1960 Lark

      Comment


      • #4
        The spec I have from A.E.A. for an Avanti starter is 295 amps @ 4 volts delivering 6.2 ft/lb of torque with the starter locked (stalled) ; . Free running speed 5300 RPM drawing 50 amp @ 10 volts. I don't understand the 4 volts; that might be all the 12 volt battery is able to supply.
        With a locked rotor on the starter motor, there is no BEMF (back electomotive force) or a voltage generated by the spinning motor to counteract the applied voltage from the power source. So, the only limit to the current in the motor is the resistance of the windings in the starter, the cables used to supply power, and the internal resistance of the power source. With 4V at the starter input terminal at 295A that would imply 13m-ohm (0.013 ohms) of starter impedance. A 4 AWG battery cable has 0.2485 ohms/1000ft so if we assume that 6ft of cable is used (3ft for each battery terminal to the starter) that is about 1.5m-ohm. The battery itself has internal resistance that will vary depending on many factors, including the size of the battery. Some data I looked at would average about 3.5m-ohms. A fully charged 12v battery is ~13.8V. So, for there to be 4V@295A across the starter, that means the rest (9.8V) is dropped across the cables and the battery internal impedance. That totals to 33m-ohms. Given about 3.5 for the battery (range of .1 to 15 for the data I looked at) and that cable of 1.5 for a total of 5m-ohms that is not out of the ballpark. A lot depends on what exact setup was used to measure it. Cable resistance, any contactors, etc. would affect things a lot. When large currents are involved, it does not take a lot of extra resistance to cause a significant voltage drop.

        When we do electronics for cars/trucks/tractors/etc one of the design specs is usually the minimum voltage available to the device and what it must operate on. Usually, a spec will say that it must work down to 9V (for a 12v application) but for something like the engine computer that runs the fuel injectors, etc. the spec is often something like 4.5V to account for the voltage droop in the cables during cold cranking. If the engine computer "dropped out" or reset due to low voltage during cranking, you'd never get the engine running.

        Jeff in ND

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        • #5
          I checked some a few years back, in order to have a frame of reference for future troubleshooting.

          Using an inductive ammeter, the kind you just lay against the wire going to the starter, I measured about 100 amps while cranking a 12 volt, V-8 Studebaker.

          While an inductive ammeter of this type is not laboratory grade accurate, several cars I tested all showed the same 100 amp load while cranking.
          RadioRoy, specializing in AM/FM conversions with auxiliary inputs for iPod/satellite/CD player. In the old car radio business since 1985.

          17A-S2 - 50 Commander convertible
          10G-C1 - 51 Champion starlight coupe
          10G-Q4 - 51 Champion business coupe
          4H-K5 - 53 Commander starliner hardtop
          5H-D5 - 54 Commander Conestoga wagon
          56B-D4 - 56 Commander station wagon
          60V-L6 - 60 Lark convertible

          Comment


          • #6
            Possible worn bearings causing armature to drag against the field. Have starter checked out. Should not draw that much current.
            don

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            • #7
              I just checked my 60 lark again and it draws exactly 100 amps while cranking.

              those little ammeters that you place against the cable are extremely useful for checking starters and generators/alternators. Sometimes they are hard to find and sometimes they are easy to find. They are very valuable tools for any tool box.
              Last edited by RadioRoy; 09-07-2012, 12:37 PM.
              RadioRoy, specializing in AM/FM conversions with auxiliary inputs for iPod/satellite/CD player. In the old car radio business since 1985.

              17A-S2 - 50 Commander convertible
              10G-C1 - 51 Champion starlight coupe
              10G-Q4 - 51 Champion business coupe
              4H-K5 - 53 Commander starliner hardtop
              5H-D5 - 54 Commander Conestoga wagon
              56B-D4 - 56 Commander station wagon
              60V-L6 - 60 Lark convertible

              Comment


              • #8
                I have checked mine with 2 different inductive meters that you just lay against the wire. I also tried my clamp on DC meter. All give me about the same reading during cranking. I will pull it off and take it to the local starter guy. Hope he can speak Studebaker.

                Thanks
                Wayne
                Wayne
                "Trying to shed my CASO ways"

                sigpic

                Comment


                • #9
                  Condition of the cables ?
                  How old are they ? The clamp on terminal ends are trash.
                  The cables can LOOK good on the outside and be corroded inside.
                  New are readily available. Even if it is the starter, change the cables.
                  Check all connections. Clean, tight, oil, rust and paint free.
                  South Lompoc Studebaker

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                  • #10
                    Donald Berg wins the prize. I tried different cables first, that didn't help. I pulled the starter apart and found that it was rubbing inside. Luckily I had another starter from the parts car. The bendix on the spare was shot, so I tore them both down, put the good bendix on the spare starter. Problem solved. Now she cranks like she should and the current draw dropped to about 150 amps.

                    Thanks to all for the suggestions and advice.

                    Wayne
                    Wayne
                    "Trying to shed my CASO ways"

                    sigpic

                    Comment


                    • #11
                      Thanks for letting us know the solution. The starter you just built should last for many years.
                      RadioRoy, specializing in AM/FM conversions with auxiliary inputs for iPod/satellite/CD player. In the old car radio business since 1985.

                      17A-S2 - 50 Commander convertible
                      10G-C1 - 51 Champion starlight coupe
                      10G-Q4 - 51 Champion business coupe
                      4H-K5 - 53 Commander starliner hardtop
                      5H-D5 - 54 Commander Conestoga wagon
                      56B-D4 - 56 Commander station wagon
                      60V-L6 - 60 Lark convertible

                      Comment

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