Hybrid vs EV mode

Discussion in 'Prime Technical Discussion' started by Pizza Driver, Oct 17, 2016.

  1. Trollbait

    Trollbait It's a D&D thing

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    The ICE's peak thermal efficiency is 40%. That means for every 33.7kWh of gasoline it burns, 13.5kWh is produced at the crankshaft. To produce that 4.6kWh(I was working with different assumptions) for the battery charge will take a little over 1/3 third of a gallon, but this doesn't consider the loses in the transaxle or energy conversions.

    I don't know who this engineer was, nor exactly what they said, but here is a simple test when making these calculated speculations.
    If it takes less gasoline to put a 20 mile charge into the battery than it does to move the car that far in hybrid mode, then Toyota needs to scrap HSD and just make series hybrids.

    About what, the battery buffer? Go back to the hybrid with a NiMH. The system keeps that battery between 40% and 60% charge. The buffer is that charged portion at the 'bottom', and uncharged portion at the 'top'. The buffer is arranged to same way for Li-ion packs. The buffer also isn't a hard limit with either battery type. The system will make use of those portions of the battery if the situation calls for it, but will charge or discharge the pack faster than normal operation to get back into into the safe zone.
     
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  2. Tideland Prius

    Tideland Prius Moderator of the North
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    The Premium and Advanced have PED and a Charging Cable Lock.

    Between the lack of a lock and the 1-dr SKS, the Premium looks to be the sweet spot for features vs. price in the US. (unless you really want cloth and hate SofTex)
     
  3. JamesBurke

    JamesBurke Senior Member

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    What's the fuel efficiency of the hybrid mode battery recharge cycle for any Prius generation or model? Has this ever been measured? Watts could be derived from SoC range. ICE run time could be timed. What would be the best way to measure fuel used? GPH/LPH per ICE run time? OBD apps like Torque have a way to calculate this? This data might give us some incite into what to expect from the Primes Charge mode.

    The test: Drive around in circles in a parking lot in HV/EV mode till your almost to the SoC where the ICE would start. Park and use an accessory load till the ICE starts then turn the accessory off. How long does the ICE run? How much gas was used? What was the battery charge C rate?

    If you run out of gas you were running the wrong test and don't forget to make a video of the whole experiment.

    ( The PED is only for therapeutic use not for enhancing performance)
     
    #63 JamesBurke, Oct 21, 2016
    Last edited: Oct 21, 2016
  4. giora

    giora Senior Member

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    OK I will give it one more try.
    When fully charged (by the tools given by Toyota, i.e. plug-in, regeneration) the battery will not accept any additional charge (that is the meaning of 'Toyota full'). You yourself argued this in another thread saying that when you start downhill after fully charged by plugging-in, the engine starts to drain this regeneration excess charge which is not sent to the battery. Now it seems you say the opposite.
    In the case of CHG mode, the system will stop it at about 80% of fully charged probably due to the higher rate used and to leave some room for regeneration opportunities. If 'fully charged' is, say, 85% SOC then 80% full is 68% SOC.
    With the 3rd gen LB, fully charged is 80% SOC (found by users with external equipment as Toyota does not report it) and not 60%SOC as you said.
     
  5. giora

    giora Senior Member

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    Maybe it will take more than 1/3 gal to get 20 (EPA) miles and the charging efficiency will then be less than 40%, we don't know for sure, my calculation exercise was done on the reported consumption, my only assumptions (for sake of calculation) were 54 and 44.
    Example:
    0.4 gal worth 13.5 kWh, 4.6/13.4=0.34 or 34% effciency
     
    #65 giora, Oct 21, 2016
    Last edited: Oct 21, 2016
  6. Trollbait

    Trollbait It's a D&D thing

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    Was this a recent thread?
    When coasting down a hill, the engine doesn't start to drain excess charge from the battery, it is allowed to spin, driven by the wheels, for engine braking. The hybrid system wants to stay below the SOC max. When near that max, the car will make more use of MG2 for propulsion. Coasting down a long hill, that isn't an option, so the battery could become charged more than usual. Thus the system will bring engine braking into play, which is also done for safety and legal reason along side protecting the battery.

    Without additional instrumentation, we do not know exactly when the engine braking begins. It could be at that max SOC point, slightly below it, or slightly above it.

    I do not recall ever claiming the max charge was a hard limit; one in which the batteries can't physically except charging.

    You have a PiP, what happens when fully charged and started in hybrid mode? Does the car still run mostly in EV for a little bit at first? Is there no regenerative braking until some of the charge is used? Can the car even start in hybrid mode, or does it revert to EV mode?
     
  7. giora

    giora Senior Member

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    The max charge or fully charged or full battery is a hard limit not because the battery can't physically except more charge but because the car system will prevent electrons to be sent to the battery at this stage.
    Since fully charged is not 100% SOC (in the PiP it is about 85% SOC) then surely one can bypass all the cars controls and charge the battery directly to a SOC higher than 85%. The point is that you cannot do it with the tools provided by the car, surely you know this!
    As for the rest of your statements/questions please read again the FAQ sticky thread in the gen 1 prius plug-in forum and the posts it redirects to.
     
  8. Trollbait

    Trollbait It's a D&D thing

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    I know instruments aiming to reach a certain value of a condition(temperature, pressure) will have a little bit of wiggle room in which overshooting the target is acceptable. This is because we are working within messy reality and not some Ideal realm.

    Batteries are chemical devices. Changes in temperature can change the SOC. The pack SOC of the PiP going a bit over the max shouldn't be treated as the end of the world by the system. After skimming almost a hundred thread pages, I see someone observed engine braking starting at about 1% before reaching SOC. This doesn't answer whether going down hill is also a factor, or if it will use ICE braking when it reaches 84% SOC from any regen braking.

    There is confusion in those threads over how engine braking works. I'm just going to assume it works like it does on the plain out hybrid until seeing a more official source.
     
  9. fotomoto

    fotomoto Senior Member

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    If it behaves the same as my Energi, full is full software-wise. My fully charged battery will revert to hybrid mode if a large regen flow comes in (downhill or heavy braking) and there's not enough "empty" capacity in the battery. As I recall, the PIP did the same as some hilltop owners here complained about this phenomenon happening at the beginning of every drive with a full battery. That is until some capacity is either used or the owner purposely doesn't allow a full charge.

    Using a scanguage in my Energi, I found this unintended by the owner hybrid mode DOES burn fuel. Probably because it uses the same software logic that the first ICE activation is a warmup mode. Just my guess.
     
    #69 fotomoto, Oct 21, 2016
    Last edited: Oct 21, 2016
  10. Trollbait

    Trollbait It's a D&D thing

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    Apperantly it does the same in the PiP. Sounds like an oversight. I don't see why anything needs to be warmed up to brake with the engine, and the car has enough charge to stay in EV afterwards.
     
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