HV battery Oil pan pre-heating in winter

Discussion in 'Gen 3 Prius Main Forum' started by Abarnabe, Feb 16, 2025 at 12:01 PM.

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  1. Abarnabe

    Abarnabe Member

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    Maybe a stupid Idea, let' see the opinions.

    Low temp affects fuel consumption on hybrid veicles harder than diesels and non
    hybrids.

    I believe transmission fluid plays a big role.
    ATF WS has the following properties:
    40°C viscosity 23
    100°C viscosity 5.3
    According to Hybrid Assist , In winter after 65 km MG1 is still at 65°C, being cooled by transmission fluid I guess that' s about a similar temp.

    The idea is to stick an oil pan silicon pad heater rated 300w 240v, connected to the HV battery with a switch that opens at 220v to protect from overdischarge and a timer to start it 2 hours before morning commuting.

    The pre requisite is to arrive at home with 60% charge the night before.

    I know the battery is deadly, I was an electrician and nothing like that should be attempted without proper protection and safety measures. Unlike AC you don't feel DC you just die.

    I installed a 2A fuse protected line coming out from the HV battery for reconditioning purposes and use it regularly.

    Hit me
     
    #1 Abarnabe, Feb 16, 2025 at 12:01 PM
    Last edited: Feb 16, 2025 at 2:14 PM
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    I'm unclear what you mean by the text I've made bold; are you referring to the engine or the transaxle (gear box adjacent to engine)?

    For either, how about an oil pan heater, the type that uses household AC current, uses a glued-on heating pad, heats things up before starting the car? It functions similar to a block heater (which warms engine coolant).
     
    #2 Mendel Leisk, Feb 16, 2025 at 12:22 PM
  3. MAX2

    MAX2 Active Member

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    Using high voltage in a hybrid, bypassing the isolated networks installed by the manufacturer, will lead to an error in the hybrid system due to current leakage to the body.

    You can warm up anything from a home network, even an engine or a gearbox.
     
    #3 MAX2, Feb 16, 2025 at 12:28 PM
  4. Abarnabe

    Abarnabe Member

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    it was indeed unclear, I meant and now edited to MG1, yes the gearbox.

    I thought about the AC outlet too, maybe it' s worth a try to see the effectiveness on mpg before making complicated mods.

    However every cent saved in gas is a cent spent in energy bill, unless one has solar panels.

    Similar to The advantage of a non plug in hybrid compared to plug in ones, you don't add costs to the energy bill :)
     
    #4 Abarnabe, Feb 16, 2025 at 12:31 PM
    Last edited: Feb 16, 2025 at 1:07 PM
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  5. MAX2

    MAX2 Active Member

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    Starting a hybrid with a warmed-up engine to +70C will allow achieving savings compared to starting at -15C.

    Electricity costs will be significantly less than fuel costs for warming up to +70C.
     
    #5 MAX2, Feb 16, 2025 at 12:36 PM
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  6. Abarnabe

    Abarnabe Member

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    when I recondition the HV battery I apply a 400w load with light bulbs without errors
     
    #6 Abarnabe, Feb 16, 2025 at 12:37 PM
  7. MAX2

    MAX2 Active Member

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    When you charge the high-voltage battery to restore it, the system does not work, the car does not move, and is turned off.

    If you use the battery for another purpose, the sensors consider the parasitic load as a leak. See this topic.

    P0AA6, detail 526, and 612 | Page 2 | PriusChat

    Besides, it is not safe!
    A small damage to this system while the car is moving can lead to a fire in the engine compartment.
    The current will be much higher than in a welding machine.
     
    #7 MAX2, Feb 16, 2025 at 12:47 PM
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  8. Abarnabe

    Abarnabe Member

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    The prewarm would be at ignition off , 2 hours before commuting, not while driving.
    Yes I'm aware of the danger.
    I was thinking to use a butil cable, they are tough and resist to mechanical stress if hit by a shovel for example, I would run it on the ground and remove it before commuting, so not connected to the car body, the car is parked in my garden and fences are locked at night.
     
    #8 Abarnabe, Feb 16, 2025 at 1:03 PM
  9. bisco

    bisco cookie crumbler

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    I think it’s a great idea
     
    #9 bisco, Feb 16, 2025 at 1:08 PM
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  10. MAX2

    MAX2 Active Member

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    I understand your desire to warm up. But why use a high-voltage battery? There are no benefits. Electric energy in a high-voltage battery is obtained from gasoline with a very low efficiency. And there is no control that the load will not accidentally lead to a complete discharge of the high-voltage battery. You can use your home electrical network.
     
    #10 MAX2, Feb 16, 2025 at 1:08 PM
  11. Abarnabe

    Abarnabe Member

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    The idea is to use an over discharge switch to protect the battery, but it seems not easy to find for that kind of dc voltage.
    The electricity would come from brake regen instead of the network, there are high taxes here on network.
    At cold start MG1 and gas engine run anyway for the first 10 minutes to warm up the cabin in winter, and the byproduct will be an almost 60% charged battery.

    Charging from 40 to 60% will warm up the battery as well, which is also desirable.

    I' m trying to sell the idea, but all feedback is very welcome
     
    #11 Abarnabe, Feb 16, 2025 at 2:10 PM
    Last edited: Feb 16, 2025 at 2:21 PM
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  12. Abarnabe

    Abarnabe Member

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    #12 Abarnabe, Feb 16, 2025 at 3:47 PM
  13. MAX2

    MAX2 Active Member

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    #13 MAX2, Feb 16, 2025 at 10:01 PM
  14. rjparker

    rjparker Tu Humilde Sirviente

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    You should preheat the engine coolant rather than the transaxle. You would eliminate most of the engine warmup fuel use and have a warm cabin right away. The electric motors in the transaxle will heat it up quickly anyway and 149f is not cool.

    What you should worry about is engine reliability in a gen3. The transaxles are nearly bulletproof.
     
    #14 rjparker, Feb 17, 2025 at 1:06 AM
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  15. Abarnabe

    Abarnabe Member

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    yes, a timer switch needs to be added before the undervoltage protection, I would propose start 2 hours before commute, cut off at 45% charge or 210v , according to Prolong user guide, it is safe to discharge at 400w rate up to 196v, so there is room to eventually discharge to 40% or 200v
     
    #15 Abarnabe, Feb 17, 2025 at 4:13 AM
    Last edited: Feb 17, 2025 at 4:19 AM
  16. Abarnabe

    Abarnabe Member

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    My goal is to lower the oil viscosity to lower fuel consumption.
     
    #16 Abarnabe, Feb 17, 2025 at 4:21 AM
  17. MAX2

    MAX2 Active Member

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    The graph shows one of my old trips at low air temperatures (up to -35).

    I had a trip the day before as well. That's why a number of systems did not cool down completely overnight.
    Look at the red line - the coolant temperature. Until it became equal to +70C+80C, the engine continued to work, consuming gasoline. This is about 16 minutes of unproductive engine operation.
    The consumption on the first section of 1 km(0.6214 miles) during this time was 34 l/100 km.(6.92 MPG)

    The temperature of the MG also increased, but it does not affect fuel consumption.
    When the high-voltage battery warmed up, it also began to help the internal combustion engine turn the wheels.
    If I had a choice of what to warm up at -35C, I would warm up the engine coolant to the maximum possible temperature.

     
    #17 MAX2, Feb 17, 2025 at 4:50 AM
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  18. Abarnabe

    Abarnabe Member

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    I' ve been searching a 230v block heater, apparently Toyota discontinued it. Any alternative available?

    If not then the cheapest alternative is oil pan heater
    I
    €7,79 | 300W Engine Oil Pan Sump Tank Heater Pad 220V Universal Silicone Oil Heating Pad Engine Oil Tank Heating Plate Wear Protect Pad
    https://a.aliexpress.com/_EJLFnsg


    Has anyone done it before? If yes what is the maximum pad size that can fit on it?
    I could go under and check but it's -4C now:)
     
    #18 Abarnabe, Feb 17, 2025 at 5:44 AM
  19. MAX2

    MAX2 Active Member

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    Tape measure in centimeters. Note that the shape is not flat and there are ribs.

     
    #19 MAX2, Feb 17, 2025 at 6:07 AM
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  20. Abarnabe

    Abarnabe Member

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    I found cylindrical heating elements

    €9,19 | DN15 1/2" Thread Tubular Heater Element 220V 0.3/0.5/1/1.5/2KW Cartridge Heater 15mm Tube Diameter Electric Heating Element
    https://a.aliexpress.com/_EvZKWzI

    what is the lenght and diameter of the toyota one?
     
    #20 Abarnabe, Feb 17, 2025 at 6:08 AM
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