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Interesting Battery Pheonenon - What gives?

Discussion in 'Gen 2 Prius Technical Discussion' started by kingofgix, Apr 30, 2007.

  1. kingofgix

    kingofgix New Member

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    I live in Colorado, and until last week had only driven my '04 Prius in Colorado and neighboring high altitude states. Last week I took a trip to Kansas, Missouri, Arkansas and Oklahoma and noticed something very interesting. Once I got part way across Kansas, the battery charge state went to 6 bars and stayed at either 6 or 7 bars (7 is the first green bar) for the rest of the trip until I got back western Oklahoma.

    Around Colorado, for the first 47,000 miles of the cars life, the normal battery charge has been 4 bars, and the battery charge state varies dramatically. On my normal daily commute across Denver I typically see everything from 2 bars (red) to 7 bars (green) and everything in between, even though my commute does not inlcude any major hills. But on this recent trip, once I dropped down to roughly 3000 feet elevation the charge state went to 6 bars and stayed at 6 or 7 for several days of driving. It got to the point that I thought something was wrong with the car, and I started trying to force the battery charge to a different state. Driving through the very hilly Ozarks, I would "floor" the car going up steep hills and noticed that the screen would show the battery charging while I accelerated as fast as I could UPHILL, with the AC on?! No matter what I did, I couldn't get the battery to go below 6 bars! I also tried stealthing around towns real slow, driving on electric only, but the engine would always come on and keep the car at 6 or 7 bars.

    Once I got to Western Oklahoma, the battery charge dropped to 5 bars, and once back above 4000 feet, the battery seemed back to "normal". As I approached home on the west side of Denver, I got back to 2 bars which is typical.

    Has anybody else noticed this? Those of you who live in the midwest, what is your normal battery charge? Does it fluctuate much? The car seems fine, and I averaged 46 mpg for the trip, but I am just curious what is going on.
     
    #1 kingofgix, Apr 30, 2007
  2. MarkMN

    MarkMN New Member

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    Location:
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    2007 Prius
    I have done all of my traveling from Minnesota down to Oklahoma and my battery gage does not fluctuate much. It is usually between half full and full up to all but the last notch (but usually just around one notch above half full). I have only seen it below half full once when I was going at about 30 mph for a while through a long stretch of speed trap road in some small town in Kansas. I think it might have something to do with the speeds you travel at. Above 50 mph, I have noticed that the battery doesn't change hardly at all no matter what you do, but at variable speeds around the city, I see it fluctuate a bit more but only in the top half of the gage. Another thing though, when I first got my Prius a few months ago, the battery gage didn't seem to fluctuate out of the top three notches for about 700 miles, then it started fluctuating more, so I always wondered if they programmed in some sort of battery brake in which doesn't necessarily make sense but I am not an electrical or mechanical engineer - I am sure weather and driving conditions had more to do with it. I just assume that the car knows what it is doing I don't need to worry.
     
    #2 MarkMN, Apr 30, 2007
  3. jewelerdave

    jewelerdave New Member

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    Could be a few reasons. Here in Colorado we do have thiner air, special fuel mixtures and the car was most likely broken in here and used to this environment. The computer controls the battery charge.
    I can see how a combination of more oxygen in the air, thicker air and changes in gas could throw the car off of what it is used too. The car does have an O2 sensor and sent information that was different from "normal"
    I would think as long as the millage stays the same and the driving is normal the comp is probably doing it for a reason.
    Could you have filled up with a richer mix of ethanol in the gas? I notice when I use E85 in mine the ICE ran more often due to the energy content difference. It also had the effect of charging the battery more.

    I may be completely off here but these are some thoughts or things to maybe check into.
     
    #3 jewelerdave, Apr 30, 2007
  4. efusco

    efusco Moderator Emeritus
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    Completely normal.
    The HV ECU is programmed to try to maintain a 60% SOC (~6 bars on the graph)...this is very easy for it to do on flat terrain, on hilly terrain it will drop below under heavy use (climbing hills) and go above when heavy regen is occuring (downhill).
     
    #4 efusco, Apr 30, 2007
  5. kingofgix

    kingofgix New Member

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    Thanks for your thoughts, but it still seems very curious to me. I'm not sure about ethanol content, but I know I wasn't using E85.

    In Missouri and Arkansas, I was driving on roads that are much more "undulating" than my typical commute in Colorado. I went up some very long, steep hills and was pushing the car hard, but the battery maintained 5 bars and was showing that it was charging as I tried to accelerate uphill. Here in Colorado, on a lesser hill, the battery discharges fairly rapidly and easily drops to just a couple of bars if I push the car to accelerate uphill. And the consistency was bizarre. The battery stayed at 6 or 7 bars for over 1000 miles of drivng at widely varying speed and over widely varying terrain. Here is Colorado I can see more variation in the battery charge state just driving around the block!

    Anyway, I 'm not worried about it but was just highly curious at the different behaviour of the car at lower altitude.
     
    #5 kingofgix, Apr 30, 2007
  6. tripp

    tripp Which it's a 'ybrid, ain't it?

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    that's funny, qix. My SOC usually stays between 6 and 4 bars. I almost never see green or purple. My commute is short (5 mi) and somewhat hilly. Though if I push the car on hills I can pretty easily knock the SOC down.
     
    #6 tripp, Apr 30, 2007
  7. priussoris

    priussoris New Member

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    I generally see 6-7 bars & every now and then I get 2 purple bars only when using ev mod. around the park. I get all but 1 green on most every highway drive up or down hill.
     
    #7 priussoris, Apr 30, 2007
  8. donee

    donee New Member

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    Hi KofG,

    Best I can remember, this type of behavior happens to my Prius when the battery gets cold. Like a cold soak down to 20 or 30 F. Once I can get the battery warm, even if its cold outside, it gets back to normal. This can be done with green housing the car - I use a brown blanket on the seats. and dropping down the rear seats and letting the sun shine right on the battery casing.

    Has it been cloudy during the day and clear at night, and have you parked the car outside during these times?
     
    #8 donee, Apr 30, 2007
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