Need advice from electronics guys about installing a power inverter and EBH.

Discussion in 'Gen 2 Prius Technical Discussion' started by Jimbo69ny, Mar 5, 2012.

  1. Jimbo69ny

    Jimbo69ny Active Member

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    My goal is to install an engine block heater and connect it to an A/C outlet inside of my Prius with a standard A/C timer in line with the EBH. I have to park my car on the city streets so plugging into an outlet isnt an option.

    My plan is to install a power inverter and connect it to the Prius 12v accessory battery. I have a 12v solar trickle charger that I would connect to the battery so it doesnt die when the EBH is in use.

    An even better solution would be to find a way to connect a temperature on/off switch to cut or give power to the power inverter when the engine temperature drops or exceeds certain limits. That way the engine is always preheated and ready to give me the best fuel economy possible. But I would need to find a thermostat that had adjustable cut off points AND I would need to find a way to monitor the engine temperature when power to the car is off.

    I am fairly experienced with both ac and dc power. Im sure this can be done, its just going to take a little planning.

    Any input?
     
  2. Jimbo69ny

    Jimbo69ny Active Member

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    You know, one factor I didnt really consider was the capacity of the oem battery. Ive heard they are pretty small. I dont know the rating of the battery but I think Im going to run into a problem there. Also, Im going to want the EBH to run around 9-10am and the solar panel wont be providing much charging power to the battery overnight :/ ....
     
  3. fuzzy1

    fuzzy1 Senior Member

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    This will kill your battery very rapidly. The necessary solar panel necessary will be larger than your car roof. Even an AC-powered trickle charger won't keep up with the EBH.
     
  4. Jimbo69ny

    Jimbo69ny Active Member

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    Yeah the more I read about this, killing the 12v battery is going to be the problem.

    I have never used a 12v engine heating pad. But would something like these be worth the time?
    Universal Flexible Block Heater Hot Pad 12v 225watt
     
  5. richard schumacher

    richard schumacher shortbus driver

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    Ditto fuzzy1. It can't be done, or rather if you do do it it will kill the 12V battery in a day.

    225W = 12V @ 19 Amps = dead battery in a few hours.
     
  6. David Beale

    David Beale Senior Member

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    The EBH is actually 400 Watts. Not even remotely practical!

    I don't know exactly what you're trying to accomplish. There is no need to use a EBH unless the temperature is very low, below 0F. Even then it's not necessary. I never use mine, though I did test it a few times. It's actually not powerful enough to do much even at 400W. When it's cold that is.
     
  7. Jimbo69ny

    Jimbo69ny Active Member

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    Im not sure your right. I have read many threads here on priuschat with posts saying it is definitely beneficial.
     
  8. fuzzy1

    fuzzy1 Senior Member

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    For competitive hypermilers, an EBH is useful for fuel savings at all temperatures, even in summer. But it is not a driving necessity in most climates, so this becomes a tradeoff between fuel savings and the hassle factor.

    But to save fuel, the heater must be powered by an external electric source not powered by automotive fuel. Using the car to power its own EBH is like having a hydroelectric dam pump its own water back uphill so it can run through the turbines again. Nothing is gained, it just wastes energy and money. (I'm not talking about hydro pumped storage to time shift energy from another plant.)
     
  9. wjtracy

    wjtracy Senior Member

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    I am still thinking about how to design a poor man's EBH but in the meantime I think you may want to start with front grill blocking and take a look at (efusco's ?) under the hood insulation pics and such to retain heat. Also go with say 0-20 Mobil-1 for those cold Cornell nights to simulate warmer lube oil. Someone recently posted impressive cold flow data on Toyota 0W-20 synthetic oil although it is unclear if that is true. If it is true I may get me some for next winter. Guess my idea for a poor mans EBH is something like a 60-watt lite bulb under the car so the heat rises...but did not take it too far as you can see.

    PS- I am into LED's these days...what can we do with some infra-RED LED's?
     
  10. fuzzy1

    fuzzy1 Senior Member

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    For this use, IR-LEDs will have no advantage over incandescent IR. It is the raw heating power that is needed. I doubt either could match a traditional EBH of similar power, because only the EBH is inside the engine block.

    When struck by -40F while vacationing in a previous car, I did use your trouble light idea under the car, combined with cardboard blocking the grill and a blanket on top the engine. And since the light was not at risk of overheating, I put in 100W. I think it all helped a bit, but an EBH would have helped much better. The area shop had the part, but the installers were already fully booked with other customers with the same idea.
     
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  11. Rebound

    Rebound Senior Member

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    You could use this inverter as long as you keep the ignition on.
     
  12. David Beale

    David Beale Senior Member

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    Yes, a -true- BLOCK HEATER consumes 700-1500 Watts. The Prius 400W one does nothing on a -20 deg night. It does speed up the warmup process when the ambient temps are above 50F. This will get you through the stages to good fuel economy perhaps 10 min. quicker. At the cost of three hours of 400W power consumption. What's that, at most $1 worth? What's it save in fuel? I doubt it saves $1. Prove me wrong! ;)
     
  13. Corwyn

    Corwyn Energy Curmudgeon

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    Why invert the power? An EBH shouldn't care about AC vs DC.

    Why do it at all? You are going to waste more fuel warming the engine with the EBH than you would just running the engine to warm it up.
     
  14. Jimbo69ny

    Jimbo69ny Active Member

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    Thats not true at all. Read the countless threads on this topic. It costs pennies to warm your engine if you plug in a EBH to a outlet in your house.

    If I couldve made my idea work it wouldnt have cost anything.

    It has been proven that you could save a cup of fuel everytime your car needs to warm up which could be once or twice everyday.
     
  15. Jimbo69ny

    Jimbo69ny Active Member

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    Thanks for your input but that would make no sense at all. The gas engine would turn on as soon as you turned the car on. Plus, the whole reason I wanted to do this was because I park my car on city streets. I wouldnt own a Prius for very long if I left it running. lol
     
  16. David Beale

    David Beale Senior Member

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    If you could have made your idea work it would have been cheaper to just let the engine run. The way you wanted to do it, you have to run the car to charge the battery, then you discharge the battery into the inverter, which powers the EBH. EVERY ONE of those steps looses energy.
    So if you just ran the engine you would only loose a little energy in that one step.
    But it would never work anyway because NO car battery has enough power to run a block heater. Keep in mind the block heater has to run for three hours before you want to drive away!
    Running the engine for about 10 min. will warm up the car better than that three hour block heater run. It would take having the car in "ready" for an hour or so to recharge the battery (if the battery could hold enough power to do what you wanted). So it's cheaper to just run the engine.

    How about a remote starter? Though if you are just trying to get better mileage, that is not a good option. Warm clothing is the best in that case. ;)
     
  17. wjtracy

    wjtracy Senior Member

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    ...non-plug in option - just brainstorming - get a Coleman catalytic heater for $35 runs on a small CNG cylinder. Find a way to get this under hood. Hack into Coleman switch to allow automated start-up via 12v timer circuit. Throw some insulation over engine. Don't burn your car down.
     
  18. fuzzy1

    fuzzy1 Senior Member

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    This works only if your electricity comes from a cheap grid, which nearly all of us have. Making that electricity with your car will always cost more, and use more fuel, than can be saved by having an EBH-warmed engine.
     
  19. fuzzy1

    fuzzy1 Senior Member

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    The block heater on my older car is also 400W. As was the one that a Montana dealer offered (but had no open time slots to install) on the previous car. Do you folks up north of the Arctic Circle, across the street from Santa's Workshop, get stronger ones?

    After my brief experience at -41 in the old car without EBH, it seemed that even a small temperature rise from the block heater would make a big difference in starting ease.
    Your electricity costs $0.80/kwh? :eek:
     
  20. Jimbo69ny

    Jimbo69ny Active Member

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    You guys are all kicking a dead horse. Its been established... It cant be done....


    On a side note, I blocked my upper and lower grills 100% and I purchased a piece of cotton insulation and wrapped the engine with it. I got the best fuel economy ever this morning (ive only owned the car a week)

    Walmart sells a small sheet of cotton insulation for $4 that was a perfect fit!
     
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