Q about charge level display

Discussion in 'Prius c Main Forum' started by birdcatfish, Mar 17, 2022.

  1. birdcatfish

    birdcatfish New Member

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    I'm the new (second) owner of a 2012 Prius c with 108K miles on it. Just getting used to it now, and wanting to better understand the hybrid battery charge level display. I live in the country and go up and down hills and around curves for every commute (20-30 mile one way average) and then do a bit of in-town driving too.

    When we test drove it, the display had 6-7 bars lit the whole time. Since having it (a few weeks) the display usually toggles between the 6 and 7 bars, but on some recent steep hills (one which I will be driving frequently) it lit up all 8 bars, then settled back to 6 or 7 bars by the time I parked back at home. Alternately, while driving around in town today and making multiple quick stops for errands, I turned it on and it was at exactly half-way (4 bars) but then worked its way back up to the 6 - 7 bars, ending at 7 bars when I parked at home (after all my hilly driving).

    I've been reading in the forum and saw a thread that mentioned "cycling" from 2 bars and all the way to 8 and the feedback was that this might be imminent battery problems. So, I'm really curious, and very much hoping, that the range of bars my car is showing within a day's driving is within normal fluctuations and not some imminent battery death situation.

    Also just wondering how to best interpret that battery display in general.

    Any feedback would be awesome. Thanks.
     
    #1 birdcatfish, Mar 17, 2022
    Last edited: Mar 17, 2022
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  2. bisco

    bisco cookie crumbler

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    congrats and welcome!
    yes it is normal, and the display is not really informative for technical reasons, mostly curiosity.

    the hybrid design uses the battery as a energy storage and release device, controlled by a computer based upon many parameters.
    you can hook up a reader to the obd connection under the dash for a better understanding of the actual state of charge of the battery, if you're interested in the more technical aspects of design and operation.

    the only time the display may be a warning is if it rapidly cycles between 2 and 8 bars. this means that the battery is losing storage capacity, and doesn't take as long to charge and discharge, similar to any battery in an electronic device.
    this warning means that it is time to start thinking about a replacement.

    all the best!
     
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  3. birdcatfish

    birdcatfish New Member

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    Okay - this is reassuring - thanks for your feedback.
     
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  4. birdcatfish

    birdcatfish New Member

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    Well, let me ask this a new way, because today it did drop down to 2 bars at the very beginning of my drive and then worked its way up to a solid 6 - 7 bars after a few minutes without dropping back down below half for the rest of the drive (about 20 minutes, hills and flat areas). So, is rapid cycling when it's switching from 2 to 8 and back again within a single drive? I think what I'm going to start seeing, now taht I'm actually driving it all the time, is it dropping at the beginning of the ride then settling back up after a few miles in the middle range of bars. Does that still sound like a healthy enough battery? Thanks for any additional feedback on that.
     
  5. jerrymildred

    jerrymildred Senior Member

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    I think @bisco is right. Unless it's going from 2 bars to 8 every couple minutes or faster, it's normal. Think of the battery as a spring. When you coast or brake, it's storing energy (more bars=compressing the spring). When you accelerate and the battery is helping the ICE, it's releasing energy and the number of bars reduces (fewer bars=relaxing the spring) to reflect that. The healthier the battery, the more slowly the state of charge (SOC) will change.

    Enjoy your new-to-you car and welcome to PC!
     
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  6. birdcatfish

    birdcatfish New Member

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    Thanks @jerrymildred (and @bisco earlier). I think that screen is so seductive, but it made me squirrely to see those bars drop even though they always came back up. I think once I get more experience driving it, read my manual cover to cover, and read through some threads here, the car will make more sense. Thanks again!
     
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  7. bisco

    bisco cookie crumbler

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    after you drive a prius for awhile, you learn to keep your eyes off of the idiot meters and on the road where they belong :cool:
    there's really no reason to worry about the battery, we see very few gen 3 replacements, 2010-15.
     
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  8. jerrymildred

    jerrymildred Senior Member

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    At ten years old, the battery has quite a bit of age on it and is at the end of the CARB states warranty. So it's not as good as a new one, but batteries normally last much longer than the warranty or the warranty wouldn't be that long. You should be good for quite a while yet.
     
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  9. birdcatfish

    birdcatfish New Member

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    Well said :whistle:
     
  10. dig4dirt

    dig4dirt MoonGlow

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    In a Prius, when you first start on a "cold" engine*, the engine will start its "warm up cycle"
    (this is programmed at certain temps)

    During the "warm up cycle", the engine will basically idle at a higher rpm, however that will
    not apply too much to the pedal response.
    During this cycle, the momentum is created mostly by the HV battery.

    So if you stomp on the gas to get going, it will drain the smallish batt down and will show you on that display.
    After it drops, it will replenish itself with the engine and brakes.

    After the warm up cycle is complete and the battery is replenished, the battery display should stick around
    the 6 bars normally. However, if you then drive in the EV portion at lower speeds, the battery and display
    will drain again.

    * a "cold" engine does not necessarily mean cold. Just under the programmed temp settings.
    So if you park it then restart it, it may have to go thru the "warm up" routine again or at least some of the
    programmed temp levels.
     
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  11. birdcatfish

    birdcatfish New Member

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    @dig4dirt thanks for the descriptive info! All these details are helpful as I get to know the car better - I appreciate you taking the time to post.
     
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  12. Rob.au

    Rob.au Active Member

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    When my c was new, I bought a ScanGauge and it helped me learn so much about the car's behaviour. After awhile I looked at the ScanGauge less and less and at some point I ended up just unplugging it and I've got it in the luggage area. I do look at the HSI and battery level occasionally but even those not so much any more - mostly because after 9.5 years driving the thing I'm very very used to it.

    birdcatfish - everything you describe sounds completely normal to me. The car's computer tends to run the show to have a target level of charge on the HV battery of around 60%, which is 6/8 bars on the display.

    As people have noted, when you first switch on, the car has a "warm-up" phase in which it behaves differently and it focuses on getting the engine temperature raised to certain set points. The engine runs continuously at this time. As people have described, even this warm-up phase has its own initial period when the power output supplied by the ICE is very limited, so this has habit of dropping the HV battery charge level down early in your drive, as your electric motors provide a greater share of the power and you'll probably feel the performance is not as good. You can just drive normally though.

    Once things settle down to normal, the car will always have a tendency towards getting the battery to 60%. It will certainly let it fluctuate, so when accelerating it will tend to drop, but any sustained type of driving you'll notice it tending back to 60%, even going uphill. If you're driving on a sustained downhill then eventually you'll get up to 8/8 (which is actually not 100% - the car won't allow the battery to charge that high to maintain a long battery lifespan). If you do hit the maximum, the car has another behaviour change, the engine will get very noisy and you'll be using the "real" friction brakes more so you may notice the braking feels different. As soon as you get off the downhill, the car will again strive to get the battery back to 60%.

    Some of this is a little bit different from what Toyota implies in the brochures, but its how the car manages its emissions, its efficiency and the HV battery lifespan.

    Everyone's regular experience will be a bit different because it depends what your regular drives are like, but I see mine drop down early in the drive, but after that normally I see 4, 5, 6 or 7 bars. If you're hitting 8 regularly on particular downhills, you might like to search the forum for an explanation of the much misunderstood "B" mode. There's nothing wrong with just driving in "D" and hitting 8, but if you're doing this consistently and then staying at 8 for any notable time because of the length of the downhill, then this is a scenario where "B" mode might be potentially useful to you. You still want to be hitting 8 by the time you get to the bottom of your hill, but it's an alternative way of managing your braking on the way down for extended downhill runs.
     
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  13. birdcatfish

    birdcatfish New Member

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    Thanks for your explanation and sharing experience. I am definitely getting more comfortable with the driving and nuances of our little c.

    Quote:
    birdcatfish - everything you describe sounds completely normal to me. The car's computer tends to run the show to have a target level of charge on the HV battery of around 60%, which is 6/8 bars on the display.
     
  14. rjdriver

    rjdriver Active Member

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    As everyone else has said, what you describe sounds very normal. The cars computer will never allow the battery to get fully drained or fully charged, although as you have noticed when on a long downhill stretch you will sometimes get eight bars. So it will vary frequently between 2 and 6-7 bars as conditions dictate.

    There are a couple of things you can do to check the condition of the hybrid battery if you are concerned. One thing every new owner of a used Prius should check is the battery cooling fan located under the rear seat. There's a vent panel under the seat behind the driver that can be removed. Make sure the filter for the fan is not clogged. Heat is one of the main things that will age a battery before it's time. I would check this once a year, or more often if you frequently drive in dusty areas or transport pets in the rear seat that might shed.

    For an actual diagnostic test that won't cost a fortune, you can try the Dr. Prius app. Hybrid battery diagnostic and repair tool for Toyota and Lexus. The basic app is free, but there is an "add on" extension you can purchase that, along with an OBD II module, will tell you how much useful life is left in the battery. It might cost more now, but a few years ago when I did mine it was $9.00. The site explains it all and the developer also recommends some OBD modules that work well with the app, most of which cost less than $20.00. A dealer can do the same test for you if you don't mind paying them somewhere in the triple digits.

    Good luck with your C. It's one of the most reliable vehicles out there.
     
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