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Inverter-how much can it take?

Discussion in 'Gen 3 Prius Technical Discussion' started by prius121212, Nov 12, 2014.

  1. prius121212

    prius121212 New Member

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    So the Prius has a 1000W inverter to covert the 220VDC to 12VDC to run the 12V components, right? Well, I am thinking of getting a number of high power 12V accessories as I often live out of my Prius for a long time. Specifically, I wanted to get a 12V grill to cook food when I am way too lazy and cold to go out and set up a legit camp fire. It draws about 50A, and I am wondering if the 12V inverter is continuous duty, and whether it can handle the load of recharging the 12V battery as needed and/ or running high power accessories.

    Now, as I understand alternators, alternators are not continuous duty. A 120A alternator cannot put out 120A for hours on end without burning up. You might be able to do 70A all day, but not 120. I am wondering if the inverter is the same.

    Last, if I use the inverter to power high power devices, am I going to kill the HV battery by constantly discharging it, activating the engine to charge the HV, then discharging it again and again, or what will happen if I put a high 12V load on the system for a long period? I suspect this scenario is basically the same as someone who uses their Prius to provide power for their house.
     
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  2. mrbigh

    mrbigh Prius Absolutum Dominium

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    The Prius electronic inverter has not been designed to withstand such a heavy load as you are presenting us but in the other hand, your signature shows you have " other type of hybrid" and not a Prius.:censored:
     
  3. bisco

    bisco cookie crumbler

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    just get a 1000w inverter and tap off the 12 volt. leave the car in 'ready' when using any electricity. if you need more power, you'll have to get an expensive unit to tap off the hybrid battery.
     
  4. David Beale

    David Beale Senior Member

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    As I recall the inverter 12V output is limited to 40 A. It's liquid cooled so overheating shouldn't be a problem as long as the car is in "ready".
    It isn't designed to run "high power accessories".
    Your biggest problem will be to ensure minimal voltage drop at the currents you are contemplating.

    Be aware, if you do toast the inverter it's a pretty big hit cost-wise. In the area of 2-4 thousand dollars.
     
  5. Easy Rider 2

    Easy Rider 2 Senior Member

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    Not a good plan. Something like Sterno or Propane would be MUCH better.
     
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  6. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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  7. ftl

    ftl Explicator

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    Some terminology definitions might help here;

    Transformer: Converts AC to AC
    Rectifier: Converts AC to DC
    Inverter: Converts DC to AC
    Converter: Converts DC to DC

    So what the Prius has between the high voltage DC traction battery and the 12V DC auxiliary battery is a DC-DC converter.

    The fuse in this circuit is 100 amps, which implies that Toyota designed the converter to supply this much current.
     
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  8. szgabor

    szgabor Active Member

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    Why are you saying this ??? just top of you head ???

    The actual fuse I believe is 100A ..

    I (and many others) have set up the Prius as an emergency generator it can put out around 1kw AC that is around 70A + 6-8% inverter and other losses (probably more for short bursts from the 12V battery) the real issue is the internal cabeling btw the inverter and the 12V battery. I personally run test with ~700W (according to Kill-a-Watt) straight resistive load (heater and few incandesent bulbs) for over an hour without anything (cables, connector, inverter) overheating .... Note, that any substantial inductive load (i.e. motors) will generate high rush in current which which might trip the 12vDC/110VAC inverter or even the converter...

    And TOYOTA sells something like this out of the box in Japan !!!

    By the way HighVoltage DC/AC ivnerter would be a better more efficient solution but that require to tap the HV battery (not for the faint harted DIY project but people did that as well). In that secenario 2 or even up to 3 KW is possible on the AC side ...
     
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  9. GregP507

    GregP507 Senior Member

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    If you need more than 1000W of DC power, I suggest you upgrade the DC-DC converter.

    I'd be concerned about overheating the alternator by using it that way. It's not designed for continuous output as a power-plant. The circuitry may stand it, but the windings may overheat and burn off the lacquer insulation.
     
    #9 GregP507, Nov 19, 2014
    Last edited by a moderator: Nov 26, 2014
  10. mrbigh

    mrbigh Prius Absolutum Dominium

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    You are barking to the wrong tree my friend. I had been involved with the Toyota Prius since 2005.

    First, get your knowledge straight up if you want to guide some nubby not to blow his Prius converter at their expense.

    The max continuous capacity of the DC-DC converter circuit is about 550 watts.

    As I said before, the OP is planning a type of outing with a lot of risk; there is other means to accomplish the same.
     
  11. szgabor

    szgabor Active Member

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    "I'd be concerned about overheating the alternator "

    What alternator ???? Prius doesn't have such things !!!! Not even a belt !!!
     
  12. ftl

    ftl Explicator

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    But even if you call the MGs alternators, which no-one does, neither one of them is in the DC-DC converter circuit between the traction battery and the 12V battery.
     
  13. GregP507

    GregP507 Senior Member

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    I call them alternators and so does anyone who knows anything about electricity, including the engineers who build them.

    What is the difference between an alternator and a generator? - Electrical Engineering Stack Exchange
     
    #13 GregP507, Nov 19, 2014
    Last edited by a moderator: Nov 26, 2014
  14. ftl

    ftl Explicator

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  15. GregP507

    GregP507 Senior Member

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  16. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Well, the Toyota factory repair manual, presumably written by their engineers, call those parts "motor-generators". I would say that the use of "alternator" in the context of an automobile would bring to mind a little belt-driven part mounted on the front of the engine.

    The motor generator in the context of the Toyota hybrid system is a three-phase AC motor.

    As previously mentioned, the DC/DC fusible link is 100A so that defines the peak load. I am not aware of a continuous current spec for the inverter.

    I think that a 12V source is a highly inefficient way to produce cooking heat. First of all, think about how much heat you will get from a grille that requires 50A at 14V: 700W.

    Now compare this to a hair dryer which consumes 1,500W of power. How long would it take you to boil a cup of water using a hair dryer? Do you have all day for that one task?

    Beyond considering the toy-nature of such a grille, also recognize that there are reasonably high power losses due to the 50A high current flow. How long of a power cable will you use to run between the car and this cooking grille?

    Suppose you have 0.1 ohm of resistance in the power cables running to the grill. That results in 250W loss at a 50A current flow. The formula is P = I^2 * R

    where P = power, I = current and R = resistance

    Can you use wires that are so thick that you will only have a total of 0.1 ohm resistance loss over the two-way run, including loss in whatever connectors you decide to use?

    The following website shows resistance vs. wire gauge and length.
    American Wire Gauge table and AWG Electrical Current Load Limits
    with skin depth frequencies and wire breaking strength


    Then you have to account for resistance between the wire and whatever connectors you use.

    IMO it would be much better and easier to use a camping stove that runs off a bottle of propane, and you would have no concern about damaging your power train while you are in the middle of nowhere, camping.
     
    #16 Patrick Wong, Nov 20, 2014
    Last edited: Nov 20, 2014
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  17. defrankond

    defrankond Member

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    Omg they are not alternators. MG1 would closely resemble a alternator in size but still not quite since it is also the starter motor for the ICE. MG2 is a electric drive/generator. The correct term is generator. Not even toyota calls them alternators and doing so makes you look like you have no idea what you are talking about. If you do not know the difference or basics you shouldn't be toying around in the electrics
     
  18. GregP507

    GregP507 Senior Member

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    I don't have to post the link again. Electrical engineers define a generator that produces alternating current as an "alternator" which is a contraction of "alternating current generator." If that's not the terminology you want to use, it doesn't make it wrong.
     
  19. Britprius

    Britprius Senior Member

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    Not wishing to get into the terminology discussion, but the Prius motors are not directly driven with the battery voltage. The battery supply is converted to 3 phase variable frequency AC supply. The motors if fed with a strait 560+ volts DC "battery boosted by buck boost" would lock the rotors and quickly burn out the stater coils.
    So yes they are AC devices.
    The real difference between the Prius "generators" and vehicle "alternators" is that the rotors in the Prius are permanent magnets. In normal alternators the rotor has a coil fed by a variable DC supply through slip rings to control the output. This system varies the strength of the magnetic field of the rotor controlling the output of the alternator.
    Further as with alternators the Prius "generators" have a 3 phase AC output. So technically are alternators giving alternating current out.

    John (Britprius)
     
    #19 Britprius, Nov 23, 2014
    Last edited: Nov 23, 2014
  20. macman408

    macman408 Electron Guidance Counselor

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    Technically an alternator or not, 'alternator' is a loaded term in the automotive industry. Toyota chose to call it a "motor-generator" for good reason - namely, that name doesn't carry the baggage that "alternator" does when associated with a car. You can call it an alternator if you want, but some people will be confused if you do - and others will try to convince you not to, in order to avoid the confusion.

    For all I care, you can call it the Information Superhighway instead of the Internet - just don't be surprised when people look at you funny. ;)