Adding battery capacity to the Prime

Discussion in 'Prime Technical Discussion' started by billvon, Dec 24, 2022.

  1. billvon

    billvon Junior Member

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    Hi all. I wanted to ask some general questions about adding battery storage to the Prius Prime. Some background:

    I have a 2017 Prime that has been great. I've changed jobs over the years, from a 6 mile commute to a 10 mile commute and now I am at a 22 mile commute (each way.) It's making it but just barely. When I drive normally I make it with maybe half a mile to spare, so I've been using hypermiling tricks (mainly drafting slow trucks) to extend that and give me some cushion. I'd rather not do that. This has been more of an issue recently even in our not-really-cold-at-all San Diego winter temps (45F in the morning) so I expect it to get better next summer, then be an even bigger problem next winter. And I don't want to have to ride on truck's bumpers to even have a chance to make it to work EV-only.

    I've been working with EVs since 1994, when we worked on a motor-integrated charger for one of Ford's early EV projects. I've been building ebikes since 1996, and I am now the head of electrical engineering for a company that is taking used EV batteries and repurposing them as grid scale storage. Which means I am comfortable working around 400-800V traction batteries and I have access to a large variety of (used) battery systems for raw materials.

    So on to the questions:
    1) Has anyone successfully connected to the HV bus in the Prime? The most likely place I can see is beneath the back seat, where the HV bus connects to the charger. Given the charger specs that would allow me to inject at least 10 amps (3-4kW) which should give me another 8 miles of range over the half hour drive, which should be more than enough. I am assuming that the battery is connected to the charger at all times but I have not verified that.
    2) Has anyone had luck injecting current into the HV bus on any of the Toyota hybrids? I know Phoenix Motorcar, A123 and a third company in San Diego (forget the name) has done this to convert regular hybrids to PHEVs but I haven't seen too many details. There are a lot of details about things like isolation boundaries, current sensor locations and common-mode noise that I could test for, but it would be a whole lot easier if someone had done testing on these things already.

    If anyone has any input on these, it would help me scope the work I'd have to do.

    Thanks and merry Christmas to everyone.
     
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  2. bisco

    bisco cookie crumbler

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    A few people hacked the pip over the years, but they were programming geniuses.
    I don’t recall anyone hacking the prime, but it would require the same skills.
    With so many off the shelf choices these days, there isn’t much interest from aftermarket sources.
    For instance, next year’s prime ups the range by 50%
     
  3. sam spade 2

    sam spade 2 Senior Member

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    This general subject has been discussed at some length; not necessarily for the Prime though.
    Have you done any searches here ?

    The general consensus is: Not a good idea. If you NEED more battery capacity, trade for a different vehicle that is designed for that.
     
  4. billvon

    billvon Junior Member

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    Yes but I have only seen general comments along the lines of "I heard of someone who got a second battery from Toyota and put it in" and "it's too hard." I also have seen several companies - Enginer, Phoenix and A123 - have done something like this, but I have seen no details. Hence the questions.

    Yes, that's the easy answer. I would like to not discard this vehicle just because it is a few miles short on range, though. And in the attempt I will learn a fair amount about the car and how to do something like this (and more importantly how not to do something like this.) That will also inform the work I do during the day, since I regularly 'spoof' batteries to think they are still in the car so they will provide power. (And design systems to then use that power.)
     
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  5. prius16

    prius16 Active Member

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  6. sam spade 2

    sam spade 2 Senior Member

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    Your vehicle is NOT "a few miles short on range". The gas engine will run.

    And a battery doesn't know or care what it is connected TO.
    That last statement tells me that you should NOT be screwing around with the hybrid battery in your car.
     
  7. billvon

    billvon Junior Member

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    The worst thing you can do for any car is to run it for 30 seconds. That generates water, but the engine oil/exhaust system does not get warm enough to vaporize it - so there it sits for days.

    Of course it does. Leaf batteries need two contactor drives to connect the battery to begin with, and they then report status via a CAN bus. Tesla packs do everything via the CAN bus which is actually a bit of a problem; the contactors are under control of the bus. Hook a Tesla battery up to a 400V inverter and it will do exactly nothing until you connect a controller to it that can send it the right data.

    And once you put it in a car it gets more complicated. EVs have "ground fault" sensors that look for common mode current and shut down the HV system if any common mode current is detected. That means that any battery system has to be 100% isolated from chassis ground,
     
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  8. Elektroingenieur

    Elektroingenieur Senior Member

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    It isn’t; those connections are made, when needed, by the CHRG, CHRP, and CHRB relays in the HV battery junction block assemblies, under control of the battery ECU assembly, and ultimately, the hybrid vehicle control ECU. See the discussion in the Repair Manual (more info) procedure for diagnostic trouble code P0D0A11.

    I’d suggest starting with Toyota’s Repair Manual, New Car Features, and Electrical Wiring Diagram to review the hybrid control, hybrid battery, and plug-in charge control systems. Those documents are written for service technicians, of course, and omit many details that would be relevant for reverse engineering, but they remain the best published descriptions of the car and how it works.
     
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  9. sam spade 2

    sam spade 2 Senior Member

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    The stuff you are talking about is NOT a part of the actual battery.
    The ACTUAL battery cells need only a resistive load for current to flow.

    It appears that you know "stuff".
    Now you need to be more careful about how you present the stuff that you know.
    So far, you are batting about 0.00 with that.

    AND......your 30 seconds estimate for running the engine likely will NEVER happen.......unless you turn it off on purpose.
    Once it starts, it will run until the internal parts partially warm up.......and the exhaust pipes are stainless steel.
     
  10. billvon

    billvon Junior Member

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    Thanks, that's useful!
     
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  11. billvon

    billvon Junior Member

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    EV batteries are systems that contain the BMS, the housing, the connectors, (usually) the contactors that disconnect and 'safe' the battery when it's not being used etc. You are talking about the cell stacks that are the energy storage part of the battery.
     
  12. sam spade 2

    sam spade 2 Senior Member

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    A "battery" is NOT a "system".
    A battery is a battery; an energy storage device.

    The extra electronics that make the battery work properly in a given application are ***NOT*** part of the battery.
    They are part of the "system", to use your word, that adapts the actual battery to the device that uses the battery energy.

    You can't bastardize the word "battery" to mean whatever you want it to mean.

    The entire energy storage and delivery system is NOT a "battery".
     
  13. mr_guy_mann

    mr_guy_mann Senior Member

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    Why is this a real concern? Your car has a gasoline engine- use it on a semi regular basis. Have ICE-only Fridays or something. It can lead to problems with gas quality if things sit too long.

    If you really want an EV, then get an EV.

    Posted via the PriusChat mobile app.
     
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  14. sam spade 2

    sam spade 2 Senior Member

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    OCD ??
    Of course it should not be a real concern.
    But people obsess over all kinds of insignificant crap.
     
  15. vvillovv

    vvillovv Senior Member

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    One solution to your question is a 2023 Prius Prime. And that at it current price would be about Half the Cost of doing the compete retrofit to the 2017 Prime, even if you could do all the work yourself.
    For Sure enough, it would still be cost prohibitive even is you had a guardian angel electrical engineer with a hobby to make you dream a reality, like has been done in the past with the engineer coversion for the gen2, the boulder hybrids gen3 conversion or the many different configurations the inventor of the manual IMA device had tested on his stable of cars before he retired.
     
    #15 vvillovv, Dec 30, 2022
    Last edited: Dec 30, 2022
  16. bisco

    bisco cookie crumbler

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    unless you own a phev, it is difficult to understand the mindset of getting to and/or from a destination within a few miles of your range.
    practically, the worst thing for the engine is to come on everyday for a mile or two.
     
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  17. sam spade 2

    sam spade 2 Senior Member

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    No it isn't.
    The worst thing is having it NEVER come on.
    If you are in an urban situation, that mile or two might take 5 minutes or more.

    As others have suggested, if it is your daily driver, you should plan an ICE only day at least every two weeks.
     
  18. bisco

    bisco cookie crumbler

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    only if toyota recommends it in the manual. we don't know how often the o/p uses the ice, only that they would like to make their commute without the ice coming on in the last few miles.

    the fact that the new prime has 50% more range negates the ice argument in more situations
     
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  19. Gokhan

    Gokhan Senior Member

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    Prius Prime already has the added battery capacity option. Simply turn on the charge mode by long-pressing the HV/EV switch.

    Anything else is a waste of time.
     
  20. vvillovv

    vvillovv Senior Member

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    I wouldn't want to try an guess if it is or isn't. I believe it very well could be one of the worse things for the engine under a specific set of circumstances, specially as the systems age and repeated occurrences.

    Lots of things in the plugins have changed between gen3 and 4 and I think there will be even more changes with gen5 for all of us to make blanket statements about, that may or may not always be how the cars behave under every condition the cars can be exposed to.
    Generally speaking, I wouldn't want to bet either way for all conditions being equal.
     
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