Heat Pump Power Draw (Traction Battery or 12V?)

Discussion in 'Prime Technical Discussion' started by Suspi, Sep 8, 2020.

  1. Suspi

    Suspi Junior Member

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    Out of curiosity, does the heat pump draw off of the traction battery or the 12V battery? If I had the car in ready mode and had a 12V battery charger connected to the 12V battery, would I be able to run the HVAC off of mains?
     
  2. drash

    drash Senior Member

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    Always off of the Traction Battery. It uses the DC/AC inverter because the compressor is AC driven. I believe it may be 25V AC but I’ll look it up to be sure. It’s different enough to make sure you go to a Toyota dealer to get it serviced.

    The fans used are 12V DC, but the compressor is AC.

    Edited to clear up the distinction between the fans and compressor.

    iPad ? Pro
     
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  3. Suspi

    Suspi Junior Member

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  4. Suspi

    Suspi Junior Member

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    I'll have to give it all a shot, but it sounds like I could probably run the fans off of mains using a 12V battery charger, but the HVAC will drain out the traction battery and start up the ICE engine to recharge it. I'm not sure if the DC-DC converter will discharge a 12V battery to charge up the HV battery, but I somehow doubt it.
     
  5. drash

    drash Senior Member

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    I’m pretty sure you can’t run the fans without powering on the A/C. In fact I purchased a battery operated fan to run without powering up the Climate Control. It attaches to the vent and I let it run while shopping with the front windows cracked. Sometime all I need is the fan to run.


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  6. Suspi

    Suspi Junior Member

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    I was hoping to do a Prius-version of RV camping with shore power. If I had a connection to mains, I'd love to be able to run the HVAC without juggling with the EV cable. The (worst) workaround would be to get a small window AC unit and slap it onto the car.
     
  7. hill

    hill High Fiber Member

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  8. sam spade 2

    sam spade 2 Senior Member

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    What is this "mains" that you keep referring to ??

    Your suggestion about a window AC unit is a joke, right ? :)
     
  9. Suspi

    Suspi Junior Member

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    Oh how I wish the Prime has a camp mode :( I tried to workaround it by setting a departure schedule for every 30 minutes overnight. It didn't work out well.

    Mains as in electrical main line from the wall. The idea is that if I use my Prius as a super gas efficient RV camper, can I somehow hack the existing HVAC to be usable off of grid power. The consensus seems to be "no".

    I already got that lovely adapter from Rob43 that allows me to plug into the NEMA 14-50 at RV campsites to charge up the car. This is sort of a logical progression of that idea.

    As for slapping on a window AC unit to the side of the car.. I mean.. I was only half joking.
    [​IMG]
     
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  10. bisco

    bisco cookie crumbler

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    why not leave it ready, like other prius campers?
     
  11. ChapmanF

    ChapmanF Senior Member

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    I guess the objective was to have it plugged in to campsite power and charging. Will a Prime do that while READY?
     
  12. Mark57

    Mark57 2021 Tesla Model 3 LR AWD

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    Ready mode lets you drive and it won't go into ready if it's plugged in.
     
  13. Suspi

    Suspi Junior Member

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    A Prime while on Ready and plugged in will power itself down after 10 or so seconds.

    A Prime while on Ready and not plugged in will drain out 100% battery in about 6 hours of HVAC.

    I guess it can't hurt to just run the AC in 6 hour intervals and charge up inbetween. Just more annoying.
     
  14. vvillovv

    vvillovv Senior Member

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    Suspi - you are talking about Ready mode in EV correct?
    Have you tried Ready mode in HV and noticed any differences?

    Or are we talking hypothetically, since you list a Gen11 in your profile.

    I think the Prime turns ON while plugged in - foot on brake press the start button, but wouldn't let the driver drive away while plugged in. I'll have to double check the behavior.
     
    #14 vvillovv, Sep 13, 2020
    Last edited: Sep 13, 2020
  15. Suspi

    Suspi Junior Member

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    Holy crap. I didn't think my old 2010 was still listed. I have a 2020 Prime XLE now.

    Ready Mode in EV will drain out the HV battery first, then boot up the ICE to recharge. I timed it to take about 6 hours of one bar HVAC in Park before it would drain out 100% battery.

    Ready Mode in HV, I assume, would behave like a normal Prius to preserve the current HV charge level. So it'll turn on the ICE once every 20 minutes and run for about 2 minutes.

    If the Prime is ever plugged in, the whole shebang shuts off after like a minute. It was a pain because I was trying to tinker with the settings while charging and it wouldn't even let me keep the computer on.

    What I haven't fully tested is the AC precondition when you set a departure time. This will start the HVAC up 20 minutes before your specified departure time so you have a heated/cooled cabin before you leave. I went through and added a departure time every 30 minutes every day to try to trick the car to always keep the precondition on. I ended up waking up in the morning to a fully charged HV battery and a dead 12V battery in the one test I did, so I'm not sure what happened.
     
  16. vvillovv

    vvillovv Senior Member

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    Yeah, Very nice writeup. I doubt anyone would know for sure what exactly happened with the 12v drain, unless looking over your shoulder as you were running the tests. And then possibly being even as unaware.

    My thing with the Prime, and I do a lot of experimenting with it too, is not trying to trick the machine, but more learning how it works, what it's looking at in the drivers behavior and adjusting it's own behavior to the way the car is handled. ie: with my 14 PiP pulse and glide and coasting in neutral still worked much like in a regular prius. Prime on the other hand, not so much. The one time I used a 1/2 mile glide in neutral on a 40 mile all EV trip to try to make the last 10 miles home while EV range was low, looked like I'd gained initially from the glide. I used other hyper-milling (extremely low speed, etc) to make to my destination with low EV range for the distance I needed to go. BUT, between the glide and my destination, the computers seemed to compensate and add a penalty in my EV range for the glide taken 10 miles back. I didn't make it to my destination in EV, even though I'd previously made the same 10 miles with the low range, but not using the 1/2 mile glide in neutral.

    It sounds strange, I know, but trying to trick this cars computers without understanding how they are crunching data, doesn't always work out the way we initially would think it should.
     
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