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  1. #1
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    Default 12v alternator conversion to 24v

    Good afternoon guys

    Long time no see.

    Do anybody have any experience with uprating a standard 12v alternator (as used on a Toyota Corolla) to a 24v alternator?

    I do have a spare alternator lying around, doing nothing, and want to experiment a little bit with converting it over to 24v.

    Once that is done, I'll want to try and build a DIY wind turbine for charging 24v battery systems (PV system).

    Any suggestions and information will be most welcome.

    Thank you.

  2. #2
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    Default Re: 12v alternator conversion to 24v

    I think if you are needing 24V then find a 24V alternator in a scrapyard somewhere..

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    Default Re: 12v alternator conversion to 24v

    So, I've got this spare alternator lying around from a Toyota Corolla, and I'm thinking of turning it into a 24v alternator. Anyone here ever tried that?
    I'm also planning to build a DIY wind turbine to charge 24v battery systems for my PV setup. Any tips or suggestions?
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    Default Re: 12v alternator conversion to 24v

    Voltage is determined by the turns on the stator.
    No easy way to convert a 12 V alternator to 24 V

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    Default Re: 12v alternator conversion to 24v

    Look for a 24v truck alternator from a scrapyard.
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    Default Re: 12v alternator conversion to 24v

    Quote Originally Posted by Grebel View Post
    So, I've got this spare alternator lying around from a Toyota Corolla, and I'm thinking of turning it into a 24v alternator. Anyone here ever tried that?
    I'm also planning to build a DIY wind turbine to charge 24v battery systems for my PV setup. Any tips or suggestions?
    try googling it, and first try making a 12V system with the alternator that you have.

    What you are attempting is not easy. Wind turbine generators use permanent magnet alternators. A car alternator needs an excitation voltage to operate. At low speed the alternator can consume more power than it generates.

    Also gearing is key.

    EDIT - this is what I have explained above. https://www.youtube.com/watch?v=tp_VI6ujKHE&t=14s
    Last edited by Fluffy; 2024/04/15 at 09:12 PM.
    Cheers

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    Default Re: 12v alternator conversion to 24v

    An alternator needs 1400 rpm to kick in and about 700 rpm before it kicks out.....gearing is a way around it but then the start up torque is pretty high.....
    Google Hugh Piggot..... Tons of info on diy generators

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    Default Re: 12v alternator conversion to 24v

    Quote Originally Posted by Grebel View Post
    So, I've got this spare alternator lying around from a Toyota Corolla, and I'm thinking of turning it into a 24v alternator. Anyone here ever tried that?
    I'm also planning to build a DIY wind turbine to charge 24v battery systems for my PV setup. Any tips or suggestions?
    Toss the diode pack and then you've got 3 phase AC......much easier to start there.

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    Default Re: 12v alternator conversion to 24v

    Quote Originally Posted by GaryFrank View Post
    Toss the diode pack and then you've got 3 phase AC......much easier to start there.
    But you then have to add a diode pack externally to turn it into DC to charge a battery.
    Cheers

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    Default Re: 12v alternator conversion to 24v

    Quote Originally Posted by Fluffy View Post
    But you then have to add a diode pack externally to turn it into DC to charge a battery.
    The regulator & diode pack is normally a combination unit.....unless it's a really old one with a separate regulator.
    Either way, you need to change the regulator to get from 12v to 24v

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    Default Re: 12v alternator conversion to 24v

    Quote Originally Posted by GaryFrank View Post
    The regulator & diode pack is normally a combination unit.....unless it's a really old one with a separate regulator.
    Either way, you need to change the regulator to get from 12v to 24v
    Thats not what you said.

    Did you watch the youtube link in my post above.

    Doesn't matter what diodes and regulator you have, you have to provide an external excitation voltage to a car alternator so it is EXTREMELY difficult to use one as a turbine generator.

    Even if you can provide an excitation voltage you can only activate it once the turbine is spinning fast enough. If you don't the battery power source for the exitation current will flatten the battery. go flat.de once the
    Cheers

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    Default Re: 12v alternator conversion to 24v

    Quote Originally Posted by GaryFrank View Post
    An alternator needs 1400 rpm to kick in and about 700 rpm before it kicks out.....gearing is a way around it but then the start up torque is pretty high.....
    Google Hugh Piggot..... Tons of info on diy generators
    That is normally the engine revs we see on the rev counter. The alternator pulley is normally half the diameter of a typical crank pulley on petrol engines and as small as a third the size of a diesel engine crank pulley turning at about 4500 maximum revs.

    This is how it used to be some 30 yrs ago when I worked on alternators.

    The idea of GaryFrank is a sound suggestion. One can then buy a off the shelf 110/220V transformer and boost the 12 to 24V and use the same rectifier. Perhaps try it using a single phase to save on the cost of a 3 pH transformer.

    The major stumbling block is the power needed to get the alternator spinning at over 2000 alternator revs to cut in. This can be as high as 750W.

    Just my observation when I built a 12V unit for a friend at a panel beater as they always have batteries to charge quick.
    Last edited by ekkekan; 2024/04/16 at 09:39 PM.

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    Default Re: 12v alternator conversion to 24v

    Quote Originally Posted by ekkekan View Post
    That is normally the engine revs we see on the rev counter. The alternator pulley is normally half the diameter of a typical crank pulley on petrol engines and as small as a third the size of a diesel engine crank pulley turning at about 4500 maximum revs.

    This is how it used to be some 30 yrs ago when I worked on alternators.

    The idea of GaryFrank is a sound suggestion. One can then buy a off the shelf 110/220V transformer and boost the 12 to 24V and use the same rectifier. Perhaps try it using a single phase to save on the cost of a 3 pH transformer.

    The major stumbling block is the power needed to get the alternator spinning at over 2000 alternator revs to cut in. This can be as high as 750W.

    Just my observation when I built a 12V unit for a friend at a panel beater as they always have batteries to charge quick.
    Unless you excite the field coils from an external source, you can spin it at 10,000 RPM and it still won’t generate any power.
    Cheers

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    Default Re: 12v alternator conversion to 24v

    Quote Originally Posted by Fluffy View Post
    Unless you excite the field coils from an external source, you can spin it at 10,000 RPM and it still won’t generate any power.
    I see a few replies about the excite. Being for a PV system there must be batteries to charge and that can provide the power for the rotor circuit. It can be wired just like a car non smart circuit with a pilot light that comes on if no power is generated.

    For me not a chance of working due to the power required to get an alternator to provide a output unless using a windmill to get a high enough speed.

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    Default Re: 12v alternator conversion to 24v

    Quote Originally Posted by ekkekan View Post
    I see a few replies about the excite. Being for a PV system there must be batteries to charge and that can provide the power for the rotor circuit. It can be wired just like a car non smart circuit with a pilot light that comes on if no power is generated.

    For me not a chance of working due to the power required to get an alternator to provide a output unless using a windmill to get a high enough speed.
    Here is the problem. If the batteries supply the excite voltage and hence current, the alternator will always be drawing current, unless you have some way of controlling it..

    An alternator/generator needs to have a coil/s rotating in a magnetic field/s, or magnet/s rotating in a coil/s.

    A car alternator has no magnets, unlike a wind turbine alternator/generator which has permanent magnets inside.

    Yes, it can be wired like a car non smart circuit with a pilot light. But that mandates an operator-controlled ignition switch.

    Thing is, unless the alternator/generator is a permanent magnet design, you need some way of controlling when and how to turn the excitation voltage on.

    Thats why/one of the reasons small wind turbines are so expensive.
    Last edited by Fluffy; 2024/04/17 at 08:22 PM.
    Cheers

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    Default Re: 12v alternator conversion to 24v

    This is probably not the intention with the alternator conversion project, but for the "ideas toolbox" using off-the-shelve components perhaps consider a 12V to 24V step up converter to achieve the same end result ?

    Like this 1800W unit in the link below for R820

    Output Power: 1800W
    Input Voltage Range: 10V-60V
    Output Voltage Range: 12V-90V
    Input Current: 40A
    Output Current: 22A

    https://www.takealot.com/1800w-40a-1...E&gclsrc=aw.ds
    Last edited by vlakkie; 2024/04/17 at 09:02 PM.
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  17. #17
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    Default Re: 12v alternator conversion to 24v

    Quote Originally Posted by vlakkie View Post
    This is probably not the intention with the alternator conversion project, but for the "ideas toolbox" using off-the-shelve components perhaps consider a 12V to 24V step up converter to achieve the same end result ?

    Like this 1800W unit in the link below for R820

    Output Power: 1800W
    Input Voltage Range: 10V-60V
    Output Voltage Range: 12V-90V
    Input Current: 40A
    Output Current: 22A

    https://www.takealot.com/1800w-40a-1...E&gclsrc=aw.ds
    Another resource for different converters. Some with like R20 courier charge.

    https://off-grid-garage.com/dc-dc-converters/
    Last edited by ekkekan; 2024/04/18 at 08:31 PM.

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