Gonna Try a 12V Heater for Winter MPG's

Discussion in 'Gen 2 Prius Main Forum' started by usnavystgc, Oct 12, 2012.

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  1. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    I recently saw that Harbor Freight is selling these 12v heaters for $10 (Its listed for $14.99 but the flyer has a coupon for $9.99). (12V Heater w/ Fan)
    [​IMG]
    I'm gonna give it a try to see if I can save some mpg's in the upcoming winter months. This (along with ccdisce's wonderful ECT spoofer) should give me summer-like fuel economy in the normally fair KY winters. I will be mounting it in front of the center console (not hard mounted just placed there) and will move it on the dash if I needed to defrost.

    I will let you know if it does what I expect. It is cheaply made but, what do you expect for $10? I wouldn't recommend it for colder climates like MN or WI etc but, in the milder areas (AL, NC, SC etc), it should warm you up pretty good (I'm hoping anyway). We'll see.
     
    #1 usnavystgc, Oct 12, 2012
  2. cwerdna

    cwerdna Senior Member

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    I'm not sure what the 12 volt outlet fuse is rated for. Hope the heater doesn't draw more than the fuse's rating.
     
    #2 cwerdna, Oct 12, 2012
  3. tv4fish

    tv4fish Member

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    Heater ad says it uses/needs a 15 amp fuse
     
    #3 tv4fish, Oct 12, 2012
  4. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    I tried it out the other day and it ran fine w/ no issues for about 15 minutes.
     
    #4 usnavystgc, Oct 12, 2012
  5. koolingit

    koolingit Member

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    The power outlets on the prius use 15 amp fuses.
     
    #5 koolingit, Oct 13, 2012
  6. bisco

    bisco cookie crumbler

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    excellent! thanks usnavy, keep us informed. some of us pip drivers are looking for just a bit of warmth to add to the heated seats so we can ev all winter without ice.:D
     
    #6 bisco, Oct 13, 2012
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  7. Britprius

    Britprius Senior Member

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    I think this is something Toyota could have improved upon. The inverter and transmission produce upwards of 2kw of heat that is thrown away by the inverter cooling system. If a small heat exchanger was plumbed into this system and the air flow put into the cabin air intake much of this heat could be usefully recovered. The coolant after leaving the heat exchanger would then go through the normal rad.
     
    #7 Britprius, Oct 13, 2012
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  8. richard schumacher

    richard schumacher shortbus driver

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    It will provide heat immediately, which is nice, but it will reduce fuel economy by some trifle. You'll be using the engine to create electricity to charge the traction battery to charge the 12V battery to run the electric heater, instead of using engine heat directly.
     
    #8 richard schumacher, Oct 13, 2012
  9. Britprius

    Britprius Senior Member

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    Also the PTC heaters do exactly this.

    Assuming this fan heater uses a couple of amps to drive the fan and it does load the electrical system to 15 amps the heat output will be around 100 watts. Not very much I'm afraid.
     
    #9 Britprius, Oct 13, 2012
  10. John H

    John H Senior Member

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    But if it is running for an hour or so before unplugging the PiP from the charger, it could take most of the edge off of a cold cabin in advance.
     
    #10 John H, Oct 13, 2012
  11. Britprius

    Britprius Senior Member

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    If the car is in a position where it can be charged why not use a mains heater rated at say 1kw plugged in. Other wise you are converting mains current to 12 volts to charge the battery then using the 12 volts to run a heater discharging the battery.

    Also if the charger stopped working for any reason "lost power supply, charger fault etc" and the heater is running off the battery that battery is going to be discharged very quickly.
     
    #11 Britprius, Oct 13, 2012
  12. SageBrush

    SageBrush Senior Member

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    I'm a fan of heated seats for winter fuel economy. I find I turn the heater on for about a minute or three depending on ambient temperature, and that is enough to tide me over until the ICE is hot enough to supply waste heat.

    OP's 12v heater sounds like a good hack, but potentially dangerous in an accident.
     
    #12 SageBrush, Oct 13, 2012
  13. John H

    John H Senior Member

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    I'm thinking simplicity. One heater, one mains connection (via the EVSE, public or private). You are right about the potential to drain the battery if the AC get's interupted. I would be sweet if there was a 12V connection that would cutout if the circuit dropped below 12.5V.

    12V Low Battery Cutoff Kit | Buy Online | Volt Electronics
     
    #13 John H, Oct 13, 2012
  14. priuskitty

    priuskitty PIP FAN

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    yeah, not enough, I have a 120 volt, 400 watt oil filled heater, left it on max temp all night, the next morning the outside temperature was 47 degrees f inside: 51 degrees f
     
    #14 priuskitty, Oct 15, 2012
  15. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    Everyone has some good input here. It does not put out that much heat. That's why I said it is fine for milder climates like KY but def not enough for the north. I know I won't be roasting in the cabin and I'm pretty sure I'll be cold. My problem is a 6 mile one way commute that takes about 12 minutes to complete. By the time I get to work, the cabin is just getting comfortably warm. Without this heater, (and ccdisce's ECT hack), the ICE runs the entire time.

    Today the outside temp was 55 f when I left home (not a good test day). I turned on the heater right away and directed the flow to my legs. I could feel the warm air w/in 20-30 sec's. By the time I got to work, the cabin was starting to get warm (just like if I used the stock heater). The difference is, I was in S4 in 45-50 sec's w/ ICE off at the first stoplight vice ICE running the entire way to work. It is def not as good as the stock heater but, I'm hoping it will provide some comfort on the milder winter days.

    As far as it being a safety hazard, I'm not sure how???? It is small, doesn't weigh a lot, stays in front of the center console without moving around. I would say its about as dangerous as an aftermarket GPS that's mounted in one of those non sliding dash (bean bag style mounts). It may be even less dangerous because I keep it low.

    I'm not trying to advocate this to anyone, I'm simply sharing my idea and will later post my results.

    My running average FE is 50.1 mpg over the last 10 tanks. This is my "summer" mileage. I'm hoping to achieve similiar winter results but, as I said earlier, "We'll see".
     
    #15 usnavystgc, Oct 15, 2012
  16. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    Yes, I'm sure it will reduce FE but I'm hoping not as much as the stock system.
     
    #16 usnavystgc, Oct 15, 2012
  17. SageBrush

    SageBrush Senior Member

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    Can you take advantage of an engine block heater ?
     
    #17 SageBrush, Oct 15, 2012
  18. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    I'm sure I can. I just haven't done it yet.
     
    #18 usnavystgc, Oct 15, 2012
  19. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    Well, we've had a few "colder" days and here's my observations/results.

    The heater is providing a dissapointing amount of heat on days colder than 40f. Using it has had the desired effect of improving winter mpg but my mpg is not equal to summer mpg as I hoped. With this heater, it is only good on the mildest of days (above 40f).

    Conclusion: It was a good try but didn't meet expectations. In my view, a waste of $10. Not recommended.
     
    #19 usnavystgc, Oct 31, 2012
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  20. Britprius

    Britprius Senior Member

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    Thanks for an honest conclusion to your test. Sorry for the waste of money as I no it is not always easy to admit defeat.
     
    #20 Britprius, Oct 31, 2012
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