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Alternative HV power tap on Prius AWD-e for high power inverters?

Discussion in 'Gen 4 Prius Technical Discussion' started by DrLithium, Aug 18, 2022.

  1. DrLithium

    DrLithium New Member

    Aug 13, 2022
    2019 Prius
    Base AWD-e
    TL;DR: The rear wheels inverter in the trunk has convenient screw terminals for HV power tap

    (If this is the wrong forum to discuss this let me know so i can put my future updates in the correct one)

    Hi everyone.

    For the past year i've been racking my brain trying to figure out how to tap the HV system to power a 3kw-5kw inverter since I want more power than the 1kw available in the 12 volt system. The problem is all the guides and previous attempts i could find was for earlier generations and they had convenient screw terminals on the battery junction box that could be tapped. The Prius 4 exclusively uses plugs. The only post i could find that tapped the Prius 4 did so by drilling holes in the junction box, feeding in wire, and soldering directly to the bus bars. That's more damage than i'm willing to do as i want to be able to easily undo my mod in case i want to sell the car in the future.

    I still never figured out how to non-invasively mod the Prius 4. But I think the subcategory Prius AWD-e throws us a big bone.

    If you look at the layout of the 4 wheel drive system, you can see the traction battery power is directly fed in its entirety into the rear inverter and then power is sent forward to the front inverter where the major stuff happens. The rear inverter doesn't use all the power, only 5.3kw, but it still has the big conductors that carry all the power. Toyota didn't cheap out and just lead a single small cable to power only the rear inverter.


    What makes it the perfect tapping point is that it's right in the trunk! Handed to us on a spare-wheel compartment platter, literally.

    Once i realized this i ran to my Prius AWD-e (2019) and ripped off the rear storage compartment insert. And there it is.


    The two cables on top are the HV cables. The cable on the right is the 3 phase motor cable for the rear wheel motors.

    What's really useful is that you can see in the picture there is a metal cover for the terminals. And that can easily be unscrewed with a 10mm hex socket.


    And there we go, direct access to the HV conductors. With convenient screw terminals too!

    They're both internally connected so it doesn't matter which one is tapped. But the right side one seems easier since the cover doesn't have a foam block there.

    Now i haven't gone further than this yet as i have to purchase a high power inverter. I wanted to be certain i could get the HV power before wasting money on an inverter.

    A difficulty I'm already foreseeing is that the terminal cover must be put back on, there is a jumper underneath that i presume is to detect if the cover is off. You can see it in the picture as that white square above the 3 motor terminals on the right. So to tap the power i'd have to drill an access hole into the cover . Alternatively i can just short the jumper and maybe cut/machine a custom cover.

    Obviously if any of you want to explore this, pull the safety plug on the battery before screwing those HV terminals.

    Nonetheless, I think this makes the Prius AWD-e a tremendously easy target to tap the HV power system. Even easier than previous models since there is no need to access the HV battery. And the power is conveniently delivered right to the trunk, where we would normally put our inverter anyway.

    If we use a custom cover, or buy another one and mod that one, then the mod is easy to undo by simply unscrewing the tap and putting the old cover back on. The mod is minimally invasive.