Losing traction battery charge in morning

Discussion in 'Gen 2 Prius Technical Discussion' started by Lowbrid, Aug 2, 2014.

  1. Lowbrid

    Lowbrid New Member

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    Hi everyone. First post. I have a 2005 Prius with about 170,000 km on it. I bought it two years ago used at 150,000 km. Everything worked fine for about 8 months, them I noticed the main battery started to drain on first start in the morning after driving a short distance. It would drop down to about 2-3 bars most days, especially on cold mornings. After reading on this forum for a bit I turned off the key locator, and it went back to normal for about 6 months, at which point it started dropping again. I haven't had any warning lights come on yet.

    I replaced the 12 V battery, as recommended here with an Optima Yellow Top, even though the original one showed no voltage drop. It actually tested higher than the new Yellow Top I got. My fear is that the traction battery is losing modules. I'm planning on testing them soon.

    My question is, if certain modules test bad, should I replace/rebalance them even if I'm not getting any warning lights? Or should I wait until the triangle of death comes on? My mileage is down a bit, but nothing major, mostly due to my short commute and the time it takes the battery to recharge.
     
  2. uart

    uart Senior Member

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  3. Britprius

    Britprius Senior Member

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    First let me welcome you to PC.
    To some degree this is normal with the Prius particularly from a cold start. The computers try to protect the engine when cold from mechanical load by using the electric motors to provide most of the motive power, thus discharging the HV battery. Aging batteries will show greater levels of discharge due to there lower capacity. Down to two pink bars depending on terrain is not unusual.
    Doing a balance charge with a grid charger "linked below" or with hobby type chargers may well bring the battery back up close to it' original capacity.
    Leaving it till a DTC is issued risks destroying at leased one module.

    Traction Battery Preventative Maintenance - Hybrid Automotive Chargers

    John (Britprius)
     
    #3 Britprius, Aug 3, 2014
    Last edited: Aug 3, 2014
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  4. ericbecky

    ericbecky Hybrid Battery Hero

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    Yes, Balancing the pack before you get an evil triangle of death on the dash is a good idea.

    Rather than mess with hobby chargers I would say a consumer grade Hybrid Battery Charger/Balancer would be a better long term investment. Install it once, then have the easily accessible charging port for all future charging/Balancing.
     
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  5. Drafty01

    Drafty01 Junior Member

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    I have a 2005 Prius that recently also did something pretty similar yesterday morning.

    My morning commute starts with a 900ft hill climb for the first three or four minutes - and ends with the same in the evening of course. This means the HV battery is pretty full in the morning.
    Yesterday, it discharged as usual up the hill, but on cresting the hill (where it would usually start charging again) it stayed discharged for about the next five minutes (undulating bendy road), only gaining charge very slowly. It eventually reached it's FULL status and acted pretty much normal for the rest of the commute - and was just fine today as well.
    The car is at almost 200,000km (approx. 124,000miles), and to my mind should not be doing this sort of thing just yet.
    I'm getting serviced in the next couple of days, so hopefully the service guys may be able to shed some light on why this happened and if it's significant or not.
    Anyone here seen anything like this?
     
  6. Britprius

    Britprius Senior Member

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    This is normal. The Prius relies heavily on the traction battery after a cold start to remove load from the engine to reduce emissions, and the fact that the start of your journey is up hill exacerbates the effect. Gentle braking will speed up the recharge if this is possible, but do not worry about it as this is perfectly normal.

    John
     
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  7. jeff652

    jeff652 Senior Member

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    If you wait for the red triangle, your odds of success with reconditioning your pack decrease significantly. You have not lost any modules *yet*, so it is not too late. If you start maintaining the battery now, you can prolong its life for a long time. Decreased MPGs and Parking the car with a full battery (on the dash display) and starting the car the next morning with a low battery or having the battery drop to a low charge after a short time driving is one of the primary warning signs of a degraded battery. I would not recommend waiting very long before reconditioning the battery.
     
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