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Toyota's Engineering Choices on Gen IV and Prime

Discussion in 'Prime Technical Discussion' started by PiPLosAngeles, Feb 28, 2019.

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  1. SteveMucc

    SteveMucc Active Member

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    I'd really try hooking both of the outlets in parallel to see if you can get sufficient power out of them before running additional wires. Worst case you can just run a jumper between the two inside the center console to give you the added oomf and not have to worry about adding additional wiring.
     
    #21 SteveMucc, Feb 28, 2019
  2. PiPLosAngeles

    PiPLosAngeles Senior Member

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    Exactly. That's where Toyota messed up on Gen IV. Judging by the observed resistance, they're using 20awg or smaller (depending on how much of the resistance is due to the outlet itself). That works when your 12v system runs at 13.8v like most alternators, but when your system runs at 12.3v as I saw in the Gen IV non-plugin, you're going to have some real problems getting 12v to the passenger compartment. Even a mild 50 watt load would drop your voltage to somewhere around 10.8v. Not good.

    EDIT - In fact, that means the outlet can never supply the claimed 120W without popping the fuse. 15 amps puts the voltage down to 7.8v, which is 117 watts.
     
    #22 PiPLosAngeles, Feb 28, 2019
  3. Prodigyplace

    Prodigyplace 2025 Camry XLE FWD

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    That sounds a lot like false advertising, which is illegal in the US and many other countries.
     
    #23 Prodigyplace, Feb 28, 2019
  4. PiPLosAngeles

    PiPLosAngeles Senior Member

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    I mentioned this to the Field Technical Specialist. His answer was, "The owner's manual doesn't say it will supply 120 watts while you're driving."

    Your Prius has the same problem. If you want to see it in action, plug a 100 watt lightbulb (75 might do it too, depending on the exact voltage your DC-DC converter puts out) into an inverter connected to one of your 12v outlets and then drive the car. The inverter will cut out within 60 seconds.*

    * Maybe cheap square wave inverters won't cut out, I don't know for sure. Some of the cheap ones will work all the way down to 10v. That will require about 85 - 90 watts before they cut out.
     
    #24 PiPLosAngeles, Feb 28, 2019
    Last edited: Feb 28, 2019
  5. CharlesH

    CharlesH CA HOV Decal #5 on former PiP

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    The air condititioning compressor in a Prius runs on high voltage AC (around 300V) from the inverter.
     
    #25 CharlesH, Mar 1, 2019
  6. CharlesH

    CharlesH CA HOV Decal #5 on former PiP

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    On the Prius, they make a big deal that for safety reasons the high-voltage traction battery is physically disconnected by a relay until the control unit is convinced that all required self tests have passed and the system is put in READY mode. I wonder how Tesla is going to get around this issue and tap the high voltage battery when the system is "off"?
     
    #26 CharlesH, Mar 1, 2019
  7. padroo

    padroo Senior Member

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    Maybe there will be another battery but not a regular 12 V as we know it. This is total speculation on my part.
     
    #27 padroo, Mar 1, 2019
  8. Prodigyplace

    Prodigyplace 2025 Camry XLE FWD

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    You mean something like a large capacitor?
     
    #28 Prodigyplace, Mar 2, 2019
  9. Vman455

    Vman455 Senior Member

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    Some versions of the Hyundai Ioniq and Kia Niro (including the hybrids sold in the US) already run with no 12V battery; they use a partition of the traction battery for 12V power.

    OP, my desktop runs on 65W, and my laptop on 19W, and they're both several years old. An easy solution here might be to get a new laptop.
     
    #29 Vman455, Mar 2, 2019
  10. PiPLosAngeles

    PiPLosAngeles Senior Member

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    If Toyota buys it, I'm all in. I'm not buying a new laptop to replace one that works fine to compensate for Toyota's poor engineering choices.

    Your desktop doesn't run on 65w unless you have nothing but a lower power CPU and no fans and no monitor. Even an i7-8700T runs at 45W. Throw in 16GB RAM, SSD, and a fanless low-power graphics card and you're already over 100W. Perhaps it idles at 65w, but that's not the same thing as doing CPU and graphics work at 65w.
     
    #30 PiPLosAngeles, Mar 2, 2019
    Last edited: Mar 2, 2019
  11. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Have you looked into using a dedicated automotive power brick for the laptop? They aren't available for all models, but they are easy to get for some. It's a DC-DC converter that lets you escape some of the inefficiency of an inverter in the middle.

    As to why they did it? I buy the idea that they aren't charging the 12v battery as aggressively as in past models in order to extend service life.

    If you can't find a direct DC-DC brick, I'd put in a dedicated high current socket. It sounds like you've been running on the ragged edge of performance anyway given that it only needed a 1.5v drop to expose trouble.
     
    #31 Leadfoot J. McCoalroller, Mar 2, 2019
    kevin.c likes this.
  12. PiPLosAngeles

    PiPLosAngeles Senior Member

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    The easiest solution in my case will be to directly ground the inverter near where it sits instead of connecting it to the negative side of the circuit. That will cut half of the voltage loss.
     
    #32 PiPLosAngeles, Mar 8, 2019
  13. zorrobyte

    zorrobyte New Member

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    Better yet, why not DIY a high amperage circuit from the 12V battery?

    You'll need a m-LVD Low Voltage Disconnect, a car amplifier install kit, patience, and wiring knowledge to do it right.

    The m-LVD Low Voltage Disconnect prevents you from draining your battery past a set voltage and has an override switch to still "start" your car if you do drain the battery. The Prius battery is tiny and they use an expensive AGM that you don't want to be overdrawing from which will ruin the battery.

    https://www.bluesea.com/products/7635/m-LVD_Low_Voltage_Disconnect/FAQ

    Amp wire install kit:


    From there, you can go nuts and put 200W of flexible solar panels & an MPPT charger on the circuit if you wanted. You could also skip the 12v system altogether and use a 300~V DC to 12V DC converter to power off the lithium pack, but I'd suggest making damn sure that you have a low voltage cutoff and know what you are doing.

    1 Output 200 V to 400 V 12 V Isolated DC/DC Converters | Mouser
     
    #33 zorrobyte, Apr 7, 2019
  14. Simtronic

    Simtronic Active Member

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    universal laptop chargers are on Ebay and Amazon they are DC to DC boosters that work well for my laptop just make sure you get a 12v one not a mains version
     
    #34 Simtronic, Apr 20, 2019
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