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Wierd battery draining situation

Discussion in 'Gen 2 Prius Main Forum' started by MechaJohn, Aug 28, 2006.

  1. MechaJohn

    MechaJohn New Member

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    I went to jury duty this morning and had to park on the ninth floor of the parking garage downtown. My prius used a combination of ICE and electric motor power on the way up, but more electric than anything. So I checked, and had 5 bars on the indicator when I turned the car off.



    I came back out four hours later and started going down the ramps. I didn't check the indicator immediately, but was watching the energy flow screen. I noticed that although I was gently pressing the brake, the car was using power from the battery to the electric motor and not regenerating. I thought it would go into regenerate mode any time you pressed the brake, or even when coasting for that matter. However, I don't know if I was going fast enough to regenerate from coasting. I know that the car starts the e-motor when you let off the brake to start rolling, but I was pressing the brake!



    By the time I got to the exit, I only had two bars on the indicator. I was in a panic. Fortunately, it charged back up to 5 bars after only a few minutes on the highway, but I am still freaked out about the battery draining!



    Anyone know what may have happened?
     
    #1 MechaJohn, Aug 28, 2006
  2. Autosmiler

    Autosmiler New Member

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    It's possible that since you just turned it on, the system was just warming up. Maybe you also had A/C and etc. running so it took from the battery? I'm not sure what happened, unless you were actually gently pressing the gas ;-)

    But you shouldn't ever worry when the battery state-of-charge (SOC) goes low because the gas engine will come on to recharge it. Only worry when you're out of gas, too!
     
    #2 Autosmiler, Aug 28, 2006
  3. Betelgeuse

    Betelgeuse Active Member

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    OK. First, MechaJohn, don't freak out. The car knows better than you when it needs to do to get the best mileage and it will do everything in its power to protect the traction battery. If the battery had drained any lower, the ICE would have just started recharging it.

    Here's what I suspected happened while you were in the parking lot: you were going relatively slowly (you were in a parking garage, after all), so you were below the 7 MPH threshold for regenerative braking. However, since the hybrid system was not in neutral (I hope), it was using a little electric power to keep the wheels rolling (i.e. simulating the "creeping" that you get in a normal automatic transmission car). I'm a little suprised that it drained as much as it did but, as I said, don't freak out. Our cars are smarter then us when it comes to battery health.
     
    #3 Betelgeuse, Aug 28, 2006
  4. MechaJohn

    MechaJohn New Member

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    <div class='quotetop'>QUOTE(Betelgeuse @ Aug 28 2006, 07:50 PM) [snapback]310859[/snapback]</div>


    Thanks Autosmiler and Betelgeuse. I know I should trust the car's intelligence. I was concerned about a malfunction since hte battery drained sooo much, though. Maybe I was merely going too slow for regen braking. I'll have to test that out. It didn't seem to have a problem in the garage at my office this afternoon, but that one is much bigger and I can get going alot faster.



    Otherwise, the car did awesome!!! I only have about 120 miles on it and am averaging 50mpg (with AC on, after all this is Houston B) ). I wonder what it will get after I break it in?



    Thanks again,

    John
     
    #4 MechaJohn, Aug 28, 2006
  5. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Another possiblity is the BMU is doing the maintainence cycle on the battery to prolong the life and performance. How many miles do you have on the car?

    Dennis
     
    #5 usbseawolf2000, Aug 29, 2006
  6. esskay

    esskay Junior Member

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    My Prius was getting a bit of a workout today, and one point I got on the throttle and the car hardly accelerated at all... was like virtually nothing was happening in response to the throttle. I flipped the MFD over to the energy screen and saw the battery in the purple (2 bars). I presume what happened at that point was the car cut off the battery and I was only getting power from the ICE, so that's why the car was gutless under throttle.
     
    #6 esskay, Aug 30, 2006
  7. Tideland Prius

    Tideland Prius Moderator of the North
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    Don't forget, while the engine is idling in its warm-up phase, even though it shows arrows from the engine to the wheels (and engine to motor to wheels), most of your power is actually coming from the battery. Try it on an empty road next time. When you accelerate a tad harder, you'll feel the car move forward but the engine doesn't rev up because the computer is trying not to use to engine to power the car until it finishes the warm-up.

    Also, as Betelgeuse said, even though you're braking, there's still power from the battery that allows you to creep.
     
    #7 Tideland Prius, Aug 30, 2006
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