Clear up an HV battery question.

Discussion in 'Gen 3 Prius Main Forum' started by milkman44, Oct 27, 2013.

  1. milkman44

    milkman44 Active Member

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    On the battery level gauge, it generally varies between two bars on the graph up to one bar from the top. I've read that this variance indicates 60% charge at the two bars and 80% charge at the one bar from the top position. So the battery is only depleted to 60%, then the ICE comes on and charges the battery. My confusion comes from several posts that say it's bad to deplete the battery and I agree that it's bad, but how do you deplete the battery if it is only allowed to vary between 60 and 80%?
     
  2. bisco

    bisco cookie crumbler

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    i think the only way to deplete the battery is to run out of gas, and even then, i'm not sure if it goes any lower than normal. you can't hurt the car by just driving it, toyota would have their hands full if they made a car like that.
     
  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    The HV Battery will sacrifice itself if you do not quit driving once you run out of gas. Do not keep trying to start the car until you have at least 3 gallons of gas in it.

    My link is to page 3, but it is all an informative read.
    Ran out of fuel AND battery!! | Page 3 | PriusChat
     
  4. john1701a

    john1701a Prius Guru

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    Those are generalizations about battery longevity... since people abuse them all the time with their other rechargeable devices. Phones don't have a engine to protect it; that's why its battery doesn't last anywhere near as long as the one in Prius.

    Hybrids and Plug-In Hybrids will prevent deep discharges from ever happening (unless you intentionally sacrifice yours by continuing to drive after having run out of gas). EV don't have that option. Pushing it will indeed shortly the life of the battery.
     
  5. stevemcelroy

    stevemcelroy Active Member

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    Or the car can be allowed to sit for an extended period.
     
  6. milkman44

    milkman44 Active Member

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    I have a 2 mile narrow winding relatively flat drive from the main road to my house, I generally run less than 40 mph so the battery is down to 2 bars, or 60% SOC when I get home. When I leave, I start out with 2 bars and by the time the engine is warm, the SOC is half way up the scale, so I'm warming and charging at the same time. I'm at 97,000 miles so I will find out if the battery will be damaged by my "depleting" it.
     
  7. David Beale

    David Beale Senior Member

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    Well, the above answers are correct but incomplete.

    First, running out of gas and continuing to drive the car or trying to start it without adding gasoline will drain the traction battery (what we call the high voltage battery) further than normally allowed by the HSD. It WILL still shut you down eventually and before you fully discharge the battery. As I recall around 10-15% charge level. Remembering that the HSD can only -estimate- the remaining charge. There is really no way to actually -know- the level in any battery except by discharging it to find out.
    Now, the danger of doing this is, if you can follow the technical gritty details, at least one cell in the battery has lower capacity than the average. If it is lower enough that when you discharge deeply it runs out, it then -charges- in reverse polarity from the current flowing through it. This is -DEATH- for most cells, including NiMH ones. This is the main reason the battery is never allowed to get even close to full discharge!

    As for shortening the life of the battery, NiMH cells actually perform better when used often and when deeply discharged, -provided- you do not reverse charge them, and remembering that you are using them heavily, and read here "using them up" heavily. They, like anything else, have a fixed life. The more you use them, the shorter their life.

    Finally, using the battery to provide power to propel the car is inefficient, compared to using the engine. It's about 50% as efficient near as we can figure. So fuel economy will suffer if you keep trying to run in "EV" mode, either by using the switch or by the way you drive.
    The reason for that inefficiency is you must eventually recharge the battery. There are losses when charging a NiMH battery, there are losses in the alternator that provides the charge current, there are losses in the inverter used to convert the electric power both for charge and discharge, there are losses when discharging that battery, and there are losses in the electric motor that pushes the car. They add together to about 50%. You bypass all these losses when driving the car directly from the gasoline engine.
    Of course this is different for the PIP. The above losses are still there when the hybrid system is operating, but most are not there when charging from the electrical grid. In that case only the charge/discharge losses, the inverter losses, and the motor losses are relevant and none of them show up in your mileage calculations.
     
  8. john1701a

    john1701a Prius Guru

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    DEPLETING means to use the battery. It's normal behavior. That happens whenever you drive.

    DEEP DISCHARGING is term you keep mixing it up with, which is totally different. That's when you push the charge-level well below the normal threshold. In other words, you'd have to drive with ZERO bars for awhile and the SOC be below 20%.

    There is nothing to be concerned about in your case.
     
  9. WE0H

    WE0H Senior Member

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    Mine sat for 8 months last winter and it was still one bar from the top when I powered it up this summer ;) Now it is in storage again and it will be 7 or 8 months before it gets powered up again.

    Mike
     
  10. tumbleweed

    tumbleweed Senior Member

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    As stated above the Prius battery SOC normally varies between 40 and 80 percent. Here is a chart that depicts the SOC for the different bars on the display. This was from a Gen 2 post but I think it is still applicable.

    Prius Battery Bars to SOC.jpg
     
  11. David Beale

    David Beale Senior Member

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    I drive Pearl S as long as I can. The alternative (FJ Cruiser) uses three times as much fuel. ;) So Pearl S only sleeps for 5-6 months. We got our first snow this past weekend, but unlike last year, it will melt they say and the roads were too warm for it to stay on them. No snow for Halloween!
    Woo hoo!

    You don't have to worry about the traction battery in storage. It's the 12V system lead acid battery that's at risk when the car is in storage. I put a "Battery Tender" on it to keep it fully charged without over-charging it.
     
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