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What size (amps) of alternator would be best for my car? (update)

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  • #16
    Modern cars, especially high end cars, have plenty of extra electrical system capacity, partly because it is assumed the owner may add some accessories. But it is unlikely that any load on a normal car would be as high as the starter. The starter is usually the only load that is not fused. The sizing of the wires and the fuses are determined by the maximum load that is expected for each item that is powered. It is true that high powered electric pumps and fans are now using more power, but the main reason for the very high powered alternators is the large number of loads. The internal regulator in the alternator tries to maintain a constant voltage in the system, regardless of the loads. Wires only overheat when they are carrying too much current (amps). Barring a short circuit in the wiring, this is determined by the load, whether it is the instrument lights or a high powered fan. The load carried by a particular wire is not related to the total load capacity of the alternator (except of course for the main power lead from the alternator to the main power panel/fuse box).

    My friend has an old Mazda with a huge row of high powered lights for rally driving at night, with something like 150 amp alternator, but when he is driving around town in the daytime with nothing turned on but the engine, he is certainly in no danger of "burning down" his car.

    If you add up the total amperage drawn by everything you might have turned on at a given time, and add 25-30 percent in alternator capacity, you should never lack for adequate power.

    In these older cars it is a good idea to inspect the wiring carefully and consider running new wires to most high powered loads. If you have any really old fuses, they should also be replaced, as they can deteriorate. It would be a shame to have a car fire because you wanted to keep everything "original".
    Trying to build a 48 Studebaker for the 21st century.
    See more of my projects at stilettoman.info

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    • #17
      Originally posted by 48skyliner View Post
      Modern cars, especially high end cars, have plenty of extra electrical system capacity, partly because it is assumed the owner may add some accessories. But it is unlikely that any load on a normal car would be as high as the starter. The starter is usually the only load that is not fused. The sizing of the wires and the fuses are determined by the maximum load that is expected for each item that is powered. It is true that high powered electric pumps and fans are now using more power, but the main reason for the very high powered alternators is the large number of loads. The internal regulator in the alternator tries to maintain a constant voltage in the system, regardless of the loads. Wires only overheat when they are carrying too much current (amps). Barring a short circuit in the wiring, this is determined by the load, whether it is the instrument lights or a high powered fan. The load carried by a particular wire is not related to the total load capacity of the alternator (except of course for the main power lead from the alternator to the main power panel/fuse box).

      My friend has an old Mazda with a huge row of high powered lights for rally driving at night, with something like 150 amp alternator, but when he is driving around town in the daytime with nothing turned on but the engine, he is certainly in no danger of "burning down" his car.

      If you add up the total amperage drawn by everything you might have turned on at a given time, and add 25-30 percent in alternator capacity, you should never lack for adequate power.

      In these older cars it is a good idea to inspect the wiring carefully and consider running new wires to most high powered loads. If you have any really old fuses, they should also be replaced, as they can deteriorate. It would be a shame to have a car fire because you wanted to keep everything "original".
      This is just generic info, that has little to do with Studes. Remember, in any vehicle, the battery provides an energy reserve. It is there for short, high demand, i.e. cranking the starter, to power accessories when the engine is idling at traffic lights, etc. Don't need a mega amp alternator to restore that energy in a few seconds, its OK if it takes several minutes, as a 35-60 amp alternator will do.

      If anyone here owns a Stude with, "a huge row of high powered lights for rally driving at night" maybe they need a 150 amp alternator. But (except within a 10 mile radius of SDC Meets) I have not seen over 25 Studes on the road, day or night, in the past 30+ years and 700,000 Stude miles. So, how realistic is it to put a mega amp alternator on a Stude, any Stude?

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      • #18
        A voltage regulator does just what its' name implies. It regulates. The alternator only puts out what is required of it. A 100 amp alternator does not always put out 100 amps every time the engine is running. It only puts out 100 amps if there is a 100 amp LOAD !!!!!!! You will not ever smoke the wiring, unless there is a load that exceeds the amp rating of the wiring.
        Bez Auto Alchemy
        573-318-8948
        http://bezautoalchemy.com


        "Don't believe every internet quote" Abe Lincoln

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        • #19
          Originally posted by fiveftsix View Post
          Think were going a little overboard over this....Geoff
          Who??? US???

          Why have a keyboard and only use it for tales of stubbing your toe on mole hills

          Making it a tale of scaling a tall mountain is much more exciting
          John Clary
          Greer, SC

          SDC member since 1975

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          • #20
            Can anyone say WHY a 100+ amp alternator is, "better" on a Stude? Run cooler and last longer because it carries a lighter, relative load, some may proffer. Power up mega accessories, others may say.

            OTOH, how many here have worn out a 50-60 amp on a Stude? How many have had problems due to the 50-60 amp on a Stude not putting out enough juice? Anyone ever actually experience any problems whatsoever with running a 50-60amp on a Stude?

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            • #21
              Originally posted by Michidan View Post
              I wouldn't guess on the cooling fan draw, check with the manufacturer. Some can really take a lot to run.
              good idea ... I ended up calling the manufacturer and discovered that the fan only draws 8 amps...now this seemed real low to me, so hooked up the fan directly to the battery with a fuse in line...started with a 25 amp fuse and worked my way through smaller fuses until they started blowing. Interesting that ATO 10 amp blade style fuses (3 of them) instantly blew when the fan turned on, yet there is no way I could get SFE glass style 10 amp fuses to blow...and I tried 2 different ones. Bottom line is the fan draws no where close to the 25amps I thought it did. It sure makes a lot of noise and moves a lot of air when its running to only consume 8 amps...ahhh, physics can be wonderful. cheers, Junior
              sigpic
              1954 C5 Hamilton car.

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              • #22
                Originally posted by Dan Timberlake View Post
                If the ammeter is wired "properly" wouldn't running the fan with the engine off show the fan amps as the change in discharge?

                Dan T
                yes Dan, it does show as discharge...just doesn`t tell me how many amps are being discharged. thanks, Junior
                sigpic
                1954 C5 Hamilton car.

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                • #23
                  Originally posted by fiveftsix View Post
                  ...An electric fan shouldn`t be running constant,it should have a thermo couple switch installed in the system so as to switch it on and off as needed....
                  Geoff
                  Agree Geoff...mine is wired that way and the fan sometimes comes on when rolling down the road, but will run constantly on a hot day if I am stuck in traffic. The engine does not have a mechanical fan installed. cheers, Junior
                  sigpic
                  1954 C5 Hamilton car.

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                  • #24
                    Originally posted by junior View Post
                    good idea ... I ended up calling the manufacturer and discovered that the fan only draws 8 amps...now this seemed real low to me, so hooked up the fan directly to the battery with a fuse in line...started with a 25 amp fuse and worked my way through smaller fuses until they started blowing. Interesting that ATO 10 amp blade style fuses (3 of them) instantly blew when the fan turned on, yet there is no way I could get SFE glass style 10 amp fuses to blow...and I tried 2 different ones. Bottom line is the fan draws no where close to the 25amps I thought it did. It sure makes a lot of noise and moves a lot of air when its running to only consume 8 amps...ahhh, physics can be wonderful. cheers, Junior
                    While you are playing with your circuit and fuses...it would be interesting to build two parallel circuits. One with the glass fuse, and the other with the blade fuse. Make the circuit "either or" with a switch from one to the other. I suspect that if you start the fan with the glass fuse, and once it is running, quickly change over to the blade fuse circuit, that fuse will not blow. I'm thinking the glass fuse might be more tolerant of the initial "start" demand required to get the fan motor going. Just a theory on my part, until someone actually performs the experiment. I'm just too lazy. I'm already late getting my garden planted.
                    John Clary
                    Greer, SC

                    SDC member since 1975

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                    • #25
                      Originally posted by jclary View Post
                      While you are playing with your circuit and fuses...it would be interesting to build two parallel circuits. One with the glass fuse, and the other with the blade fuse. Make the circuit "either or" with a switch from one to the other. I suspect that if you start the fan with the glass fuse, and once it is running, quickly change over to the blade fuse circuit, that fuse will not blow. I'm thinking the glass fuse might be more tolerant of the initial "start" demand required to get the fan motor going. Just a theory on my part, until someone actually performs the experiment. I'm just too lazy. I'm already late getting my garden planted.
                      That`s exactly what I was thinking...but not that I`m lazy...just too focused on trying to catch-up on all the have-to`s that I put off before taking off for a 7 week holiday in Southeast Asia. Now that I`m back I`m am struggling to get the have-to`s done, dealing with family issues and a former employer who can`t seem to get my pension and benefits sorted out. On top of that we had an exceptionally early spring here and the dang Stude isn`t close to coming out of it`s winter hibernation yet...and as I said in the opening post it`s a long story made short but I now have to address this alternator issue because last season the charging system baked the battery and slapping a new battery in the car will not resolve the root cause of the problem. All rather minor since I do not have go work anymore and that`s an awesome feeling. cheers, Junior
                      sigpic
                      1954 C5 Hamilton car.

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                      • #26
                        [QUOTE=karterfred88;986678]Not knowing which Delco alternator you adapted from what 63 Chevy, makes it hard to guess what you have vs. what you need. That alternator output could be as low as 25-35 amps, thus your needle dip with headlamps and fans running. My guess would be a 55-65 amp replacement would be more than enough and leave you room to add some other accessories. QUOTE]

                        After snooping around on the `net, I think the alternator is a DE 10DN series Delco Remy that puts out a max. of 42 amps. I`m guessing your guess of 55-65amps is the way to go. Thanks, Junior
                        sigpic
                        1954 C5 Hamilton car.

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                        • #27
                          Thanks for all the responses, conversation and sharing on this thread. I purchased a 10SI series Delco-Remy style alternator that puts out a max of 63 Amps and has an internal regulator. It`s a bolt in swap for my old-school alternator that I took out, and now I have to do some wiring up-grades, pulley alignment, and get a new belt and battery and the charging system should be up to snuff for many years to come. Cheers, Junior
                          sigpic
                          1954 C5 Hamilton car.

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                          • #28
                            Junior, I believe your choice will serve you well.

                            Where in SE Asia did you get to go? I have been all over there. Japan and the Philippines are my favorites. My wife is Japanese-Okinawan.

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                            • #29
                              Originally posted by JoeHall View Post
                              Junior, I believe your choice will serve you well.

                              Where in SE Asia did you get to go? I have been all over there. Japan and the Philippines are my favorites. My wife is Japanese-Okinawan.
                              Those two places (Philippines and Okinawa) are on my hit-list to visit. Mrs. Junior and I have travelled to SE Asia four times now...we keep going back. This year`s trip was to Thailand (Bangkok and north), then to Lao, and then finished off with 3 weeks in Cambodia. Thanks for asking. Junior
                              sigpic
                              1954 C5 Hamilton car.

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