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Meaning of bars on MFD for traction battery

Discussion in 'Gen 2 Prius Technical Discussion' started by Artis, Aug 1, 2008.

  1. Artis

    Artis Junior Member

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    2008 Prius
    Hi all, First post and new owner as of yesterday. The site and comments have been very helpful. The dealer spent about 5 minutes with us on delivery and considering he couldn't explain how to change the station on the radio, 5 minute may have been too long. In any case, the info here has saved us (I've been lurking for a few days reading) along with some hours reading the manual (which isn't bad, I thought). Now if I could pose a question.

    I'm curious about the bars on the MFD which indicate charge status. Do these represent stored capacity? It seems so, but that doesn't seem to explain a behavior I noticed in the drive through (burger, not liquor store). I entered the line with all but two bars active and the line was fairly lengthy. On exiting, I was down to two bars and the gas drinker kicked in to maintain charge. I should also note that it was very hot and the AC was running constantly.

    If the bars denote stored energy such as KW/H, then I'm a bit surprised at the drain rate. If they measure V drop under load, then the behavior is not surprising as there may not have been enough charge time. Has anyone got a table of how much drain various activities such as AC places on the batts? The batteries are NiMH if I'm not mistaken and with a grand total of 60 miles on them, we could be talking about no more than the dreaded new battery silly owner watching his new toy syndrome.

    Hope this is not a duplicate. Couldn't find a thread on quite this topic though some posts on new batterys and break in time were helpful. I basically just want to make sure I don't have an infant mortality thing going on.

    Thanks in advance for any thoughts or comments.
     
    #1 Artis, Aug 1, 2008
  2. morpheusx

    morpheusx Professor Chaos

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    Three
    First what you saw is normal, if its extremely hot outside and you sit in traffic without moving or at a drive thru with the A/C on it only takes about 10 minutes for the battery to deplete (from the normal 5 or 6 bars). This is completely normal, think of it as a major benefit of a Hybrid, because you weren't burning any gas while sitting in line.

    In these type of cases where the batt. becomes depleted like that you may also notice that your acceleration will lag a bit for a minute or two (while its still pink/purple)

    You don't necessarily need to avoid this because there is no harm in this happening other then fuel efficiency. When this happens typically your fuel economy will dip for the next 5 minutes of steady driving as the battery charges (it charges back up that quick). To avoid this you can try adjusting your power usage on the A/C. I like the Auto setting at 75 for the summer. But if I'm stuck in line at a drive thru or traffic I frequently just manually change it to the recycle and the lowest fan speed.

    I hope this helps.
     
    #2 morpheusx, Aug 1, 2008
  3. Artis

    Artis Junior Member

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    That is a great help. Its good to hear that I'm seeing behavior consistent with someone else.
     
    #3 Artis, Aug 1, 2008
  4. JimboK

    JimboK One owner, low mileage

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    Morpheusx is correct that what you're seeing is normal behavior.

    A point to clarify: An empty battery display does not mean empty battery. The car goes to great lengths to protect the battery, in particular avoiding overcharging or over discharging. It maintains state of charge (SOC) between ~40% and ~80% -- which happen to correspond to the display's readings of "empty" or "full." See this for a good discussion on the relationship between the display and SOC, and their relationship to voltage.

    I know of no one who has constructed a table that shows current draw with various devices. I have add-on instrumentation that monitors current, among other things, and I've thought about putting together such a table. Just haven't taken time to do it.

    I can tell you that AC easily pulls 10A+ with heavy demand. With a 6.5Ah battery and the narrow range of what the display actually represents, you can get a handle on why the bars disappeared so quickly.
     
    #4 JimboK, Aug 1, 2008
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