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Inverter-how much can it take?

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

  1. GregP507

    GregP507 Senior Member

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    Everyone thinks I'm talking about them. I hate to name names, therefore it seems to be left to the imagination to assume they are the target. My beef is not with anyone who has an opinion about the subject, and almost everyone who has participated in this thread was doing so in good faith.

    For the answer, just look to who was making the most comments directed to the person, not the topic.
     
  2. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    Prius is undoubtedly a better "generator" than most of what you can buy at Home Depot. Just keep in mind there is a 300W to 400W overhead of running the car. This draw comes off of the HV battery. So if you leave the Prius READY with no draw, it will consume a few hundred watts. Powering 1KW of load, that's less noticeable than charging your phone at 10W.

    If power in your area is frequently out, there are lots of good 240V to 120V step down converters. Most are 240VAC, but the first thing they do is rectify to DC. We've found that supplying them with the Prius traction battery power directly keeps them happy and they spit out 120VAC no problem. You can buy a 15KW system (I think, maybe 20KW) for about $2K last I checked. We don't have power outages here, but even so I have all the important stuff on backup batteries and the Prius ready to connect into the main panel. A good benefit is that if I shut off the main supply to the house, hook the Prius into the panel, that is enough to fool my solar inverter that the grid is operational and it will continue outputting 11KW.
     
  3. szgabor

    szgabor Active Member

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    OH Yes it is readily available but more expensive and a little more risky (involved) to implement as a DIY project.

    I considered it but stuck to the the 12V system. Many people (bobwilson for example but others, as well) actually approached this as an engineering project and made scientific measurements. Before and even after doing it. I have a 1KW continues and 2KW surge sinus wave DC/AC inverter I build the thing after considering others works. I tested it for real (that is how I discover that my fridge won't work because of high surge current when motor starts)...

    Moreover several people successfully used their system during natural disasters (I was lucky till now). And then GregP507 "tells" that the "alternator" will melt down ... Wth ???

    And yes, there are successfull projects using the HV batteries for up to 3KW...

    To add... in Japan Toyota sells an option for no other reason but an emergency generator powering a house for about 24 hour on full tank of gas !! (GregP507 check this out I think the spec is around 1KW) it is expensive though maybe Toyota missing something Greg knows ???

    Also the 2010 and later models have a 125A fuse protecting the inverter (converter) and a think another on the battery side which is 150A neither is an easy fix if blows.... I personally put a 95A fuse btw my inverter and the 12V battery so YES I am not trying to get the max out that is still close to a 1kw on the AC side if the inverter efficency is really 93% :)
     
    #43 szgabor, Nov 24, 2014
    Last edited: Nov 24, 2014
  4. GregP507

    GregP507 Senior Member

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    Of course I'm being misrepresented here. I said I'd be worried about overloading it, nothing more. I suggest you write a letter to Toyota to straighten them out for not already endorsing your idea.
     
  5. macman408

    macman408 Electron Guidance Counselor

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    That's an interesting idea. So you're using one of these 10s of kW converters with the solar? I assume your solar inverter steps down the production appropriately to maintain ~120V, since you're presumably not using 11 kW typically. I suppose maybe in my case, I might even be able get that going with one of the puny 1 kW 12V inverters, since my house's unoccupied "idle" power draw is usually only 150-200 W.

    I'm about to get solar myself, though a pretty small system because we don't use much power. I'm not likely to attempt something like this though, since we rarely have power outages here too. And also, I'd be afraid of frying something in the car by either drawing too much power, or the solar inverter trying to backfeed it to the car...
     
  6. szgabor

    szgabor Active Member

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    I am not misrepresenting anything you wrote QUOTE:

    "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."

    Please note that during the "charge" cycle the "alternator" is working within design specification. In essence runnig the ICE in the optimal 1280 RPM and recharges the HV battery etc... just like when somone stuck in traffic !!!

    With this application (up to 1KW power generarion), one concern (I think), which you did NOT mention, but would be legit is whether or not "using up" HV battery charge up cycle is worth it. Because that is happening. The HV battery is limited to a 'few thousand' charge cycle.

    The Prius HV battery doesn't really care about miles it cares about charge cycles !!! (and extreme temperatures as well)
     
  7. GregP507

    GregP507 Senior Member

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    I stand behind every word, even though some have done their damnedest to take it out of context.
     
  8. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    Using it this way, it is really only 1 "charge cycle". The battery drains down to 2bars, then the engine restarts and it only runs to charge it up to 3 bars. This continues until it runs out of fuel. So it is cycling between 43% and 51.5% which is pretty much ideal.
     
  9. szgabor

    szgabor Active Member

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    No it is not !!! It is a fraction of a cycle but that is count !! It is cumulative !

    Yes that is correct !!!

    But you are still using the HV charge cycle(s) up if I use your numbers it is about 1/10 of a full cycle per "charge up" depending on the load it would happen a few times per hour.. If I recall correctly under my test 1.5 hour running 650W (pure resistance load) the ICE was starting up somewhere every 10-15 min for about 3-5 minutes so that means about half full cycle per hour give or take...

    So this use wears the HV battery (like city driving does as well NOT the miles driven) but not putting any miles on the car.... again this is a fact and just needs to be factored in by anyone who implements this application.
     
  10. SageBrush

    SageBrush Senior Member

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    ^^Szagabor,
    Use of the battery is going to age it, but trying to calculate something akin to 'cycle equivalents' for partial charge/recharge cycles is far, far from linear.

    I vaguely remember USBseawolf publishing a graph some years ago showing that the Prius traction battery is good for 100,000 (or was it a million ?) 'cycle equivalents' if SOC is kept between 45% - 55%. So the occasional use of the car as an emergency/camping tool is not going to show up as a traction battery lifetime hit you care about.
     
  11. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Source: Prius - UPS Project

    In October 2005, I bought our first Prius, a 2003 model. The first modification in November 2005 installed a 1 kW/1.2 kW, modified sine wave inverter. We have used it at least once per year, every year since and in April 2011, 4 days and 6 hours.
    [​IMG]
    I installed a fold-down, mount so in operation, the inverter was in a normal, mount to radiate the heat. But otherwise, it is folded-up:
    [​IMG]

    ARCHITECTURE

    This is the overall system:
    [​IMG]
    A key design objective is the ability to provide 110 VAC power to the cabin while driving. This provides power of a laptop that can run Prius monitoring. But to achieve this requirement, the inverter was modified to add a remotely power, relay:
    [​IMG]
    [​IMG]
    Power to operate the relay is activated by an ignition switch enabled, power source, the 12V cigarette.

    MOUNTING

    The original, 12V mount:
    [​IMG]
    There is plenty of air-space above the 12V battery for the inverter. So I used a piece of cardboard to make a template:
    [​IMG]
    This was used to cut 3/8", quality plywood, foldable mount:
    [​IMG]
    A baseplate holding the two hinges complete the basic configuration. I did have to nibble out a ground bolt access.

    [​IMG]
    So the hinged mount folds down in high-power operation to provide plenty of cooling air. In normal operation, it is vertical:
    [​IMG]

    OPERATIONAL SCENARIO

    In normal operation the traction battery provides power to the DC-to-DC converter that substitutes for an alternator in ordinary cars. This water-cooled inverter is able to operate at maximum power because it is already cooled. So normally we see this cycling:
    [​IMG]
    At minimum power, the traction battery sits around 55.5%. But when the load draws the SOC to 52%, the engine starts and recharges the traction battery using MG1, the 18 kW, unit. If the load is near maximum, this cycle becomes shorter. The key fact is the engine cycles ON/OFF as necessary to keep the traction battery between 52-55.5%. So the traction battery current switches between charge, 4 to 5 A, and discharge, -0.8 to -5 A. At maximum power load, it is almost a 50% duty cycle.

    Now this is the part the non-Prius aware people do not understand. The Prius engine only runs when energy is needed and otherwise is off. When it does run, it is at high-efficiency power point. Ordinary engine-direct, emergency power, generators are incapable of do thing. They have to partial-throttle to deal with fractional loads and this is exceptionally inefficient!

    Another fault of traditional, emergency generator is handling maximum or near maximum power. Being air cooled, they have to use fuel enrichment to keep from burning out the exhaust valves. In effect, they are adding exhaust gas cooling by running a rich mixture.

    But the biggest risk is emergency generators do NOT have a catalytic converter. Their exhaust is rich in carbon-monoxide, a poisonous gas. Every year, we read about families poisoned, some dead, because their emergency generator poisoned them. In contrast, it is all but impossible to get enough carbon monoxide in Prius exhaust except to possibly get a headache. Then there is the noise.

    The Prius is so quite it can be barely heard outside of the property line. In contrast, emergency generators have nothing remarkable for a muffler and can be heard half a block away.

    TEST POWER

    To test the power capabilities, a resistance heater was powered by the inverter while DC voltage and current were measured:
    [​IMG]
    • 13.94 V., 1.1 A. with inverter OFF
    • 13.94 V., 1.7 A. with inverter ON and no load
    • 13.83 V., 50.3 A. with heater on lowest setting (~ 700 W)
    • 13.75 V., 71-74 A. with heater on medium setting (~ 1 kW)
      In this mode, the inverter ran at normal temperature in the 50 degree (F) evening. The system was stable and ran without a problem or attention. This is the mode used for the fuel-burn testing.

    • 11.48 V., 89-90 A. with heater on high setting (~ 1 kW)
    Now the measured fuel burn:
    • 0.25 gal/hour with 1 kW load
    • 0.06 gal/hour w/o load
    This is from an 11.5 gallon, useful capacity, tank. This means > 40 hours at full load without refueling a full tank and 191 hours, ~8 days, without a load.

    So this is how it rates relative to other emergency generators:
    [​IMG]
    So it is certainly competitive. Best of all, you can drive to the a gas station to fill-up when bad weather is forecast.

    CONCLUSION

    I do not care if anyone adds an inverter for emergency power from their Prius. There are emergency generators and of course, 'cursing the darkness.' I have already sent my requests to Toyota: it works; it is safe, and; efficient. We also have one in our 2010 Prius but that is another report. But my next version will tap the traction battery directly.

    Bob Wilson
     
    #51 bwilson4web, Nov 27, 2014
    Last edited: Nov 27, 2014
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  12. Tony D

    Tony D Active Member

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    Bob, your working knowledge of these things never ceases to amaze me!
     
  13. GregP507

    GregP507 Senior Member

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    Nice job, but I have a question if that's OK. Why a 1000W inverter to run a laptop? I have a 400W inverter that plugs into the lighter socket and runs anything I might ever use in the car.
     
  14. bwilson4web

    bwilson4web BMW i3 and Model 3

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    It is for house emergency power. We have had at least one power outage every year and used the Prius for emergency power:
    • six weeks ago - equipment failure led to a 4 hour outage with low, 40F, outside temperatures. The Prius provides enough power for the 700W, gas furnace, fan.
    • April 2011 - tornadoes tore up the TVA transmission lines and we camped out at home 4 days and 6 hours.
    • summer heat - it can power a 5000 BTU, window air conditioner in the bedroom so we can sleep.
    The cabin power only needs to provide less than 50W to power the laptop. At that low level, I'm not worried about heat in the trunk. But when providing house-power, the trunk is open and the inverter laid down for optimum cooling.

    This has also turned out to be useful at remote sites and when trimming trees on our property:
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    Bob Wilson
     
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  15. szgabor

    szgabor Active Member

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    not sure about plugin-prius ... but 2010/2012 classic has a max 120W rating on the lighter socket ! and if not mistaken it IS fused with a 10A fuse so no way to get 400W that way ... but a normal laptop may not need really more than 120W YMMW

    (I did blow that fuse with my 2010 model using an air-pump rated less than 200W)
     
  16. Handygeek

    Handygeek Member

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  17. GregP507

    GregP507 Senior Member

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    I guess I'm lucky I never had to run the plug-in inverter to full capacity.
     
  18. GregP507

    GregP507 Senior Member

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    There are many threads about mods which claim to have done this successfully. I've also seen such inverters offered for sale on the web.

    I wouldn't recommend them, because that's not what the Prius is designed for, but many people swear by them (and sometimes at me for not recommending them) but to each their own.
     
  19. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Nice unit and perfect for the 28 module, Prius. Retail prices, $4,000, are a little high.

    Bob Wilson
     
  20. Handygeek

    Handygeek Member

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    I met Doug Gaede & saw his system.
    I got my two inverters from him.
    He's not the only one with highly-successful real-world applications.
    I'm not sure I understand why there would be even a hint of doubt about it.
    The 12v method is an alternative - I'm not sure how they compare in terms of available power and efficiency.