Optimal time to charge HV battery

Discussion in 'Gen 3 Prius Technical Discussion' started by zebekias, Sep 23, 2014.

  1. zebekias

    zebekias Member

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    We know the ICE runs optimally at mid to high load (upper half of ECO). If energy was generated, stored, and used without any losses it'd make sense to charge when the ICE would run inefficiently at low load. The idea would be, increase the load artificially via the generator to force the ICE into the high efficiency area. The reality is, there are huge energy transformation losses, and thus this strategy would backfire. From the moment I learned about ICE efficiency I assumed it's best to gently charge when the ICE would have to run at optimal efficiency anyway.

    Does scangauge show when the HV battery is being charged by the ICE? When does the software actually charge the battery? I want to confirm my thinking.
     
  2. David Beale

    David Beale Senior Member

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    You can display the battery current using the Scangauge. It will show charge and discharge by including a + and - sign. Generally, the most efficient charging is through regen. where you recover and can use about 50% of the energy that you would otherwise waste in brake heat. It isn't huge but every bit helps.
     
  3. SageBrush

    SageBrush Senior Member

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    In an ideal world, the battery would only charge from regen and excessive downhills;
    Discharge would never exceed the amount from the above recharge

    Here is reality:
    1. Help your car avoid low power, low torque ICE use. Hello, P&G
    2. Avoid ICE power demands much over ... say 70%. If you have to lose some speed on that hill -- OK. And forget about passing while going up hills.
     
  4. zebekias

    zebekias Member

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    I'm already driving with ICE efficiency in mind, I try to keep the HSI in the upper half of ECO. Obviously when I'm about to regen on a long hill I can be liberal in using up most of the battery. When it gets tricker is highway driving when there will be little to no regen. I got good results with using up the battery just prior to road segments that would keep the ICE in peak efficiency. The idea is, I get slightly worse mpg in those segments by having to drag along the generator, but coasting a mile with the ICE off is the big win.

    Now I wonder if an even better strategy is to avoid having to charge via the ICE. On the highway just avoid using all electric mode by avoiding speeds lower than 80kph. At 90kph it can still go all electric on you if the SOC is high, but that's the exception and not the rule.

     
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