Charging Prius 12v with CTEK charger question.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by dolj, Mar 5, 2014.

  1. dolj

    dolj Senior Member

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    I posted this in another thread, but thought I'd break it out into its own post.

    For those familiar with the CTEK MXS 5.0 charger: is it normal to stay on stage 7 (float) or should a healthy battery be on stage 8 (pulse) by the morning? I've been able to leave the battery on charge continuously for 3 full days and it hasn't gone past stage 7. I also put the battery on charge for three nights in a row (driving the car in-between during the day) and again it only got to stage 7 each time, but not get to stage 8.

    Again thanks for any info on this.
     
    #1 dolj, Mar 5, 2014
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    I have a CTEK 3300 (3.3 amp). It'll typically go to green lights (the charger satisfied the battery's fully charged) if I leave it hooked up overnight. With a borderline battery they just sort of hang in limbo, never showing fully charged symbology.

    Try driving the car for a few days (assuming it's charged enough for the car to work normally). This will burn off any "surface charge" (I don't know the ins-and-out of what this is, just that a freshly charged battery will read high), which would cause over-high reading. Then, measure the voltage with a digital multimeter. 12.6 volt or higher and it's 100%. 12.4~12.5 is iffy. Even lower even worse.

    If this is the original battery it's definitely time for a new one.
     
    #2 Mendel Leisk, Mar 5, 2014
  3. nh7o

    nh7o Off grid since 1980

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    I would want find out what the CTEK uses as the criterion for going to pulse mode. In my experience with batteries, pulse charging is the most important technique to maintain and reclaim battery capacity. So it really ought to be possible to manually select that mode. Pulse charging breaks up sulfate crystals over time. I use pulse mode before float mode if I am going to reclaim a battery.
     
    #3 nh7o, Mar 5, 2014
  4. dolj

    dolj Senior Member

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    The manual is not too clear, hence my question. At this stage (stage 7) it supplies 13.6V at 5A and says it will do this for a maximum of 10 days. It also says the charge cycle will restart if the voltage drops. The pulse stage (stage 8) it supplies a varying voltage between 12.7V - 14.7V and a varying current between 5 - 2.5A

    The first stage (de-sulphation) does this, I believe. But on the charging cycles I've done, it skips quite quickly through this stage, which leads me to believe that de-sulphation is not required.

    All of these figures are for the AGM setting.
     
    #4 dolj, Mar 6, 2014
  5. dorunron

    dorunron Senior Member

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    #5 dorunron, Mar 6, 2014
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    I've seen the lights on mine go to green (done charging, except for maintenance token charge), then flip back to amber (not done). I guess for a borderline battery.
     
    #6 Mendel Leisk, Mar 6, 2014
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