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Max Power Output of 12V 100A Alternator & 12/230V Converter: Calculations & Connecting 5 Units

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  • #1 17339940
    Anonymous
    Anonymous  
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    #2 17339989
    sanfran
    Network and Internet specialist  
    Yes, it will be a multiple.

    Added after 27 [minutes]:

    The real power is what the load will be.
    The alternator has something like a voltage regulator, which aims at a certain voltage at the output (in the case of automotive alternators it is about 14.5V).
    Now the alternator is electrically loaded, i.e. power is drawn from it. The voltage at the output drops, the regulator, striving to maintain it, increases the current flowing through the rotor (in the alternator, it is generated in the stator), the rotor puts greater resistance on the machine that drives it, and that's it.
    And at some point, either the drive will not perform and the RPM will drop, or the rotor will get the maximum excitation current - and the voltage on the alternator will start to drop below the rated value - we have reached the limit.
  • #3 17340069
    Anonymous
    Anonymous  
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    #4 17340110
    sanfran
    Network and Internet specialist  
    Yet another aspect should be considered.
    Each electric machine has parameters such as instantaneous power, hourly power and continuous power.

    Car alternators (and it seems to me that my colleague is thinking about something like that) are not designed for continuous full load operation.
  • #5 17340135
    Anonymous
    Anonymous  
  • #6 17340166
    jack63
    Level 43  
    grz_w wrote:
    Drive one by engine, propeller, water ... and several others by magnetic wheels.

    What are these "magnetic wheels"?
    grz_w wrote:
    Make 600W of the inserted, for example, 150W.

    Why not MW ??? After all, it's as simple as perpetual motion machines have already been invented.
  • #7 17340167
    vodiczka
    Level 43  
    grz_w wrote:
    Make 600W of the inserted, for example, 150W.
    Is my friend thinking about perpetual motion machines? :?: :cry:
    If the alternator power (at the output) is to be e.g. 600W, the mechanical power (rotating the alternator rotor) must be> 600W

    grz_w wrote:
    12V 100A alternator. I assume that it is driven to maximum performance. I connect the 12 / 230V converter. What is the real power
    12V x100A = 1200W
    Let's assume that the 12 / 230V converter has an efficiency of 90%
    1200W x 90/100 = 1080W
    With a lower efficiency of the converter, your colleague will not get 1kW
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  • #8 17340293
    Anonymous
    Anonymous  
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    #9 17340305
    kkknc
    Level 43  
    12V is the rated voltage. 100A is the rated current efficiency, but at 14V. You can pull a little more from the alternator. Except that modern alternators are not built for maximum continuous power for a long time. And the efficiency of the alternator is about 50%, so to take a kilowatt from it you need to put two .....
  • #10 17340529
    kortyleski
    Level 43  
    grz_w wrote:
    . I know the laws of dynamics P.

    grz_w wrote:
    . I do not want to put in the example 100W and pick up more from one alternator, only from several.

    What's the difference with one or several? The laws of physics taught in elementary school have not changed so far. The power delivered to any miracle box inside must always be greater than the power received. Basically not power, but energy. It can't be helped.

    Added after 10 [minutes]:

    Why did I mention energy. Because power is a imprecise concept. Of course, each of us has access to a device in which we put 100 W and receive 1000W. Only ignoring the losses, if I put these hundred watts in for 10 minutes, I will receive 1000W for only a minute.
    And yet another. We take a can of canned food and throw PLN 1 every minute for 100 minutes. After 100 minutes, we close the experiment and in a fraction of a second we become the owner of as much as one hundred zlotys. And yet we only put in single zlotys.
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  • #11 17340584
    vodiczka
    Level 43  
    grz_w wrote:
    One is driven by a motor, the next by magnets. That's what I mean, maybe I wrote it too haphazardly
    What is the difference whether they are rigidly connected with a cardan shaft or a magnetic clutch?
    You will always take out less than you put in :)
    grz_w wrote:
    I do not want to put in the example 100W and pick up more from one alternator, only from several.
    Then say in plain text "this is what I want to put in and so much to pick up" and close the topic or move it to Hyde Park.
  • #12 17340841
    Anonymous
    Anonymous  
  • #13 17341181
    iron64
    Level 41  
    I rather doubt your technical education, it is not about boasting, but about the fact that in order to receive, for example, 6kW of energy, you must provide these 6kW plus what will be lost, even in heat. Everything has its efficiency, the efficiency of electric motors is high, but it is still 0.97-0.98. The efficiency of the alternator is much lower.
    The method of connection you have come up with (theoretically, as I understand it) is suitable for perpetual motion. You deliver 100W and you receive 600W. if you expand your machine park in such a way, you can produce electricity on a global scale. The question of how many alternators will you use, right?
    Tell my friend, have you read what you wrote yourself?
    Nothing is for free, just. If someone says otherwise, it means they are not looking wide enough. A child may think that they are getting toys for free, but we know that someone had to pay for them.
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Topic summary

✨ The discussion revolves around the power output capabilities of a 12V 100A alternator when connected to a 12/230V converter, particularly when multiple units are used. It is established that the real power output is influenced by the alternator's voltage regulation and efficiency, with a maximum theoretical output of 1200W (12V x 100A). However, practical limitations arise due to the alternator's design for intermittent use rather than continuous full load operation. The efficiency of the converter is also a critical factor, with estimates suggesting around 90% efficiency, leading to a maximum usable power of approximately 1080W. The conversation highlights the importance of understanding the relationship between input and output power, emphasizing that energy losses must be accounted for, and that one cannot expect to extract more power than is input, especially in the context of multiple alternators. Experimental testing is suggested to determine the limits of the system under load.
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FAQ

TL;DR: A 12V 100A alternator makes ~1.2 kW DC; a 90% inverter yields ~1.08 kW AC. “12V x100A = 1200W.” [Elektroda, vodiczka, post #17340167]

Why it matters: This helps DIY power builders and off‑grid tinkerers size alternator–inverter systems without overloading, voltage sag, or false expectations.

Quick Facts

How much AC power can a 12V 100A alternator deliver through a 12/230V inverter?

Multiply voltage by current for DC watts: 12V × 100A ≈ 1200W. With a 90% efficient inverter, expect about 1080W continuous AC. Keep surge margins for startup loads. “12V x100A = 1200W.” [Elektroda, vodiczka, post #17340167]

What does “real power” mean in this setup?

Real power is what the load actually draws at the regulated output. The alternator’s regulator targets about 14.5 V and increases rotor current to maintain it. At the limit, voltage sags below nominal as excitation maxes out. [Elektroda, sanfran, post #17339989]

Can I run a car alternator at full load continuously?

Not safely. Alternators have instantaneous, hourly, and continuous ratings, and full load is not a continuous-duty condition. Heat and wear accelerate at max output. “Car alternators are not designed for continuous full load operation.” [Elektroda, sanfran, post #17340110]

How much mechanical power do I need to get 1 kW electrical?

Budget about double due to alternator losses. With ~50% alternator efficiency, 1 kW electrical needs roughly 2 kW mechanical at the shaft. Add inverter losses on top when sizing the prime mover and belts. [Elektroda, kkknc, post #17340305]

Will connecting five alternators give five times the power?

In principle, yes, outputs add. In practice, limits appear when the drive lacks torque or alternators hit excitation ceilings, causing voltage drop. Ensure correct RPM, adequate torque, and proper regulation for each unit. [Elektroda, sanfran, post #17339989]

Do magnetic wheels or clutches provide extra (free) power?

No. A magnetic coupling only transmits torque and adds its own losses. It cannot increase net energy. “You will always take out less than you put in.” Use them for isolation, not gain. [Elektroda, vodiczka, post #17340584]

How do I safely find the maximum load my alternator-inverter can handle?

Try this: 1) Assemble the system and connect meters for voltage and current. 2) Add loads gradually (e.g., tools, lamps), tracking voltage. 3) Stop when voltage sags or temperatures rise. That’s your practical limit. [Elektroda, Anonymous, post #17340069]

What happens if I overload the alternator?

The regulator drives maximum rotor current. If demand keeps rising, output voltage drops below the setpoint and the drive may slow. That indicates you have exceeded the alternator or drive capability. Reduce load or increase torque. [Elektroda, sanfran, post #17339989]

What inverter size matches a 100A 12V alternator?

Base it on ~1200W DC available. With a ~90% inverter and real-world losses, select around 800–1000W continuous AC to leave margin for heat and surges. Avoid sizing the inverter above sustained alternator output. [Elektroda, vodiczka, post #17340167]

Is a 100A alternator rated at 12V or 14V?

Automotive alternators are rated around 14V at the terminals. “100A is the rated current efficiency, but at 14V.” Compute watts using the regulated voltage, not the nominal 12V label. [Elektroda, kkknc, post #17340305]

Can I get more energy by stacking generators or stages?

No. To deliver 6 kW you must supply more than 6 kW input due to losses. Electric motors can be 0.97–0.98 efficient, but alternators are lower, so stacking increases losses, not output. [Elektroda, iron64, post #17341181]

How do I know if my alternator speed is sufficient under load?

Watch voltage. Regulators hold near 14.5 V until excitation max is reached. If voltage remains stable under load, RPM and torque are adequate. Droop indicates insufficient speed or torque. Increase drive RPM or reduce load. [Elektroda, sanfran, post #17339989]

What do instantaneous, hourly, and continuous ratings mean for alternators?

Instantaneous is short bursts. Hourly is limited-duration duty with cooldown expectations. Continuous is safe indefinitely within thermal limits. Size your loads to the continuous rating, not the peak or hourly values. [Elektroda, sanfran, post #17340110]
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