Lithium install connect to prius side of terminals instead of HV OEM battery side?!

Discussion in 'Prius PHEV Plug-In Modifications' started by Flying White Dutchman, Feb 12, 2012.

  1. Flying White Dutchman

    Flying White Dutchman Senior Member

    Joined:
    Dec 29, 2007
    4,374
    304
    0
    Vehicle:
    2012 Chevy Volt
    In a contactor based plugin installation when the contactors would fail the lithium higher voltage would be connected to the oem battery pack.

    this maybe overcharging the oem pack.

    so wy not connect the lithium pack to the prius side of the terminals

    look at the picture.. green is where you normally connect and red is where i would connect

    question : if the contactors of your lithium pack would fail and you shutdown your prius then there will still be energy going to the inverter
    will this harm it?!
    :pray:
     
    1 person likes this.
  2. seilerts

    seilerts Battery Curmudgeon

    Joined:
    Mar 7, 2010
    3,326
    1,470
    38
    Location:
    Santa Fe, NM
    Vehicle:
    2005 Prius
    The inverter will see the potential, but it won't do anything with it. It would be like having an appliance plugged in but turned off. This won't harm the inverter, but it does create a potentially dangerous situation where the lithium battery is no longer isolated if contactors have failed. For example, in a car accident, you would have live conductors.

    The Enginer system connects as you show, to the red-circled posts. There, the safety is that the Enginer DC converter will not operate if the car is not in Ready.
     
    2 people like this.
  3. Flying White Dutchman

    Flying White Dutchman Senior Member

    Joined:
    Dec 29, 2007
    4,374
    304
    0
    Vehicle:
    2012 Chevy Volt
    so i have to be in a car accident and have failed contactors at the same time
    thats a big IF and i stil have the fuse on the litium battery pack and a disconnect plug..
     
    1 person likes this.
  4. seilerts

    seilerts Battery Curmudgeon

    Joined:
    Mar 7, 2010
    3,326
    1,470
    38
    Location:
    Santa Fe, NM
    Vehicle:
    2005 Prius
    Both approaches carry some risk. If you connect to the battery side of the relays (green), then the lines running from there to your contactors are always live. If you connect to the frame wire side (red), then the risk comes if you have a contactor failure (such as, you have an accident that causes them to stick). The risks in either case are small and there are tradeoffs.
     
  5. Flying White Dutchman

    Flying White Dutchman Senior Member

    Joined:
    Dec 29, 2007
    4,374
    304
    0
    Vehicle:
    2012 Chevy Volt
    when i have a accident then the prius contactors can also fail beside the ev200 contactors
    so in that i see not difference.
    i have 2 battery pcaks and both of them when not used are cuttoff from the prius with contactors
    if one of them would fail, so the ev200 plugin contactors or the OEM contactors i have the same situation.
     
    1 person likes this.
  6. seilerts

    seilerts Battery Curmudgeon

    Joined:
    Mar 7, 2010
    3,326
    1,470
    38
    Location:
    Santa Fe, NM
    Vehicle:
    2005 Prius
    I guess the one thing I wonder, how will your lithium packs overcharge the Prius NiMH pack? Are they over 260V?
     
  7. Flying White Dutchman

    Flying White Dutchman Senior Member

    Joined:
    Dec 29, 2007
    4,374
    304
    0
    Vehicle:
    2012 Chevy Volt
    at 240 volts you will charge your oem pack its 72 x 2,9-3,6 volts ( depleted and full )
     
    1 person likes this.
  8. Flying White Dutchman

    Flying White Dutchman Senior Member

    Joined:
    Dec 29, 2007
    4,374
    304
    0
    Vehicle:
    2012 Chevy Volt
    new picture

    wy not min on oem side and plus on prius side.
     
    1 person likes this.
  9. seilerts

    seilerts Battery Curmudgeon

    Joined:
    Mar 7, 2010
    3,326
    1,470
    38
    Location:
    Santa Fe, NM
    Vehicle:
    2005 Prius
    If Lithium == LiFePO4, that you charge to 3,65V/cell, which later falls to 3,35V/cell after surface charge dissipation, for 241,2V in your pack. Then there will be an additional voltage drop when the Lithium packs "sees" the NiMH pack. The Enginer people normally run at 235-240V. I do not see you having a problem with overcharging the NiMH pack in the case of contactor failure.

    Next, in your latest picture, by passing one of the wires through the current sensor, it will cause SoC errors, unless you replace the battery ECU. Is that what you mean by Plus?
     
    1 person likes this.
  10. Flying White Dutchman

    Flying White Dutchman Senior Member

    Joined:
    Dec 29, 2007
    4,374
    304
    0
    Vehicle:
    2012 Chevy Volt
    plus is in + side ;-)
    with the engineer sets when you keep the caar standing still and the dc-dc converter runnig at itrs 240 volts it wil overcharge the oem battery.
    you have to use the hal effect sensor otherwise the prius will set a DTC
     
    1 person likes this.
  11. seilerts

    seilerts Battery Curmudgeon

    Joined:
    Mar 7, 2010
    3,326
    1,470
    38
    Location:
    Santa Fe, NM
    Vehicle:
    2005 Prius
    Okay, I thought you were talking about BMS+

    So, let's go back a little.

    241,2V is the most that your LiFePO4 pack could provide, in the case of stuck contactors. This is 1,436V per NiMH cell, assuming no voltage drop. This is about 100% SoC. It is not something that you want to do all the time, but it is not a catastrophe.

    With the current sensor, you have two problems. If you bypass it, then at >14A current, you will get a DTC, as you say. If you pass your wire through it, as shown in your picture, then the Coulomb counting algorithm in the battery ECU will calculate that the battery is being drained faster than is actual, and you will drop out of EV mode too soon. So you need either a custom battery ECU, or you need to spoof SoC, but I think with spoofing, you get a negative recal (forced charge of the battery by the ICE) when you shut things down. I believe BMS+ (now BMS2) solves this problem. You may wish to contact the designer, it is well worth the money if it works.

    blank
     
    GG707 and dave77 like this.
  12. Flying White Dutchman

    Flying White Dutchman Senior Member

    Joined:
    Dec 29, 2007
    4,374
    304
    0
    Vehicle:
    2012 Chevy Volt
  13. lopezjm2001

    lopezjm2001 Senior Member

    Joined:
    Apr 14, 2009
    1,144
    400
    5
    Location:
    Sydney Australia
    Vehicle:
    Other Electric Vehicle
    Model:
    N/A
    If you connect directly to the OEM terminal side (no current sensor bypass). The OEM battery ECU will count down coulombs via the hall effect current sensor and adjust SoC accordingly and it assumes that the OEM HV battery pack full capacity is 6.5ah and as SoC nears 40% the Hybrid ECU will call for the ICE to come on aggressively to charge a HV battery which is supposedly on low charge. The OEM battery ECU does not know that you have a 20ah lifepo4 connected in parallel and never will. This is where using a BMSplus to fake the SoC is needed.

    The current sensor bypass is needed to avoid a DTC for high battery current mismatch. The Hybrid ECU compares currents it measures/calculates against current reported by the battery ECU and will throw a DTC if difference in current is generally greater than 16/19 amps. This DTC is known to disable the ICE and stall the Prius and thus putting the driver at a high risk of causing an accident.

    Both the SoC spoofing device and the current sensor bypass are critical for the use of any added HV battery packs in parallel on a Gen2 Prius.
     
    3 people like this.
  14. chenyj

    chenyj Member

    Joined:
    May 22, 2009
    96
    115
    0
    Location:
    Troy, Michigan
    Vehicle:
    2004 Prius
    Model:
    II
    That is a wise approach. When the vehicle is off by the driver or in an accident, the relays will open and there is no close loop for the PHEV pack going to the OEM traction battery nor the OEM inverter.

    Great idea!!!
     
    1 person likes this.
  15. mrbigh

    mrbigh Prius Absolutum Dominium

    Joined:
    Sep 6, 2005
    3,686
    679
    2
    Location:
    Long Island, NY
    Vehicle:
    Other Electric Vehicle
    Kudos for Flying White Dutchman .:cheer2:
    So F.W.D. deserves a brand new Enginer Kit as a reward. Hurray !!
    Not to mention that I have been using the same connection approach since my first DIY PHEV conversion on December 2006 and rolling 'til today.
     
    2 people like this.
  16. mrbigh

    mrbigh Prius Absolutum Dominium

    Joined:
    Sep 6, 2005
    3,686
    679
    2
    Location:
    Long Island, NY
    Vehicle:
    Other Electric Vehicle
    Kudos for Flying White Dutchman .:cheer2:
    So F.W.D. deserves a brand new Enginer Kit as a reward. Hurray !!
    Not to mention that I have been using the same connection approach since my first DIY PHEV conversion on December 2006 and rolling 'til today.
     
    1 person likes this.
  17. Flying White Dutchman

    Flying White Dutchman Senior Member

    Joined:
    Dec 29, 2007
    4,374
    304
    0
    Vehicle:
    2012 Chevy Volt
    yes a 8 kw please
    ;-)
     
    2 people like this.
  18. Flying White Dutchman

    Flying White Dutchman Senior Member

    Joined:
    Dec 29, 2007
    4,374
    304
    0
    Vehicle:
    2012 Chevy Volt
    mm just thinking
    doing this would bypas the toyota implimented resistor relay that switched just before the mains are both closed... to prevent damage to the inverter.... so would this maybe be a bad idear?

    edit

    under normal opereation you power on the prius then OEM will close and use the precharge and then the plugin contactors wil close so i guess you dont have that problem anymore.
     
    1 person likes this.
  19. lopezjm2001

    lopezjm2001 Senior Member

    Joined:
    Apr 14, 2009
    1,144
    400
    5
    Location:
    Sydney Australia
    Vehicle:
    Other Electric Vehicle
    Model:
    N/A
    This is a link to how to do the Hall Effect Current sensor bypass:

    Hall Current Sensor Bypass CalCars.PNG

    Prius PHEV Schematics - EAA-PHEV

    OEM Battery Emulator Circuit.PNG

    It was interesting to see that a Battery Tap Emulator - EAA-PHEV battery tap emulator was used before the BMSplus was available. This battery tap emulator could be used to fool the battery ECU so that the OEM NiMH battery could be removed. Then you could replace the OEM battery with a Lifepo4 HV battery. Most of the electronics is not needed as the BMSplus already does the spoofing so the 14 resistor//capacitor voltage divider is all that is needed to fool the battery ECU to think that there is a NiMH battery pack connected.

    When you consider that the effective SoC that can be used for a NiMH pack is 40% (2.6ah) and it has a high self-discharge/heating and has a low power density it makes sense to ditch the old OEM NiMH HV battery pack and replace it with a Lifepo4 pack.

    The NiMH pack has a o/c voltage of 191v at SoC of 40% which would correspond with a Lifepo4 cell voltage of 191v/72cells=2.65v.

    The NiMH pack has a o/c voltage of 242v at SoC of 80% which would correspond with a Lifepo4 cell voltage of 242v/72cells=3.36v. The Lifepo4 pack has a charged resting voltage of 3.35vx72cells=241.2v which is close.

    Obviously the rate of change of voltage on a NiMH battery is a lot faster than the Lifepo4 which would probably confuse the OEM battery ECU causing it to throw a DTC. Obviously that by removing the original NiMH battery pack that you no longer need a Hall Effect Current Sensor bypass or the HV battery fan assembly which takes up a lot of valuable battery space and weight.
     
    2 people like this.
Loading...