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Battery charging question

Discussion in 'Gen 3 Prius Main Forum' started by Wxboy73, Jan 2, 2012.

  1. Wxboy73

    Wxboy73 New Member

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    Recently I was in stop and go traffic and the car didn't act the way I thought it would so I want to see if anyone else has noticed this and/or can explain what was happening.

    Conditions were stop and go traffic with go speed at 1-6 mph, mostly 2-3 mph. Temperature was in the 30's, it was after dark, and the heat was on in the car. I have a scanguage so I expected the battery to drop to 40% and then have the ICE come on charge the battery to 50% and turn back off. This happen but not the way I expected. The ICE did come on at 40% but it seemed to go in and out of charging while the ICE was running. The gph on the scangauge would bounce back and forth between .18gph and .52gph. I didn't time it to see if there was a pattern but you could hear the change in the engine and I could see the change on the scanguage. I don't know why it wasn't charging the battery the entire time the ICE was on. I did turn the heat off at one point to see if that would change things but it didn't. I've only been in traffic like this once before but that was almost a year ago I don't remember if the car did the same thing.

    I'm used to running a power inverter in the car with the car sitting in the garage and when doing this the car doesn't go in and out of charging when the ICE is on. When the battery drops to 40% SOC the ICE turns on and charges the battery to 50% and shuts off. Of course the car is in park when doing this so maybe that changes things.

    I'm trying to find out if this is normal and if so why is the car not charging the battery the entire time the ice is running? It seems like a waste a fuel to run the engine and not charge the battery at the same time when the engine came on because of the low SOC to begin with.
     
    #1 Wxboy73, Jan 2, 2012
  2. qbee42

    qbee42 My other car is a boat

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    Most likely the ICE was burning fuel to make heat.

    Tom
     
    #2 qbee42, Jan 2, 2012
  3. Wxboy73

    Wxboy73 New Member

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    That's what I was thinking but when I turned the heat off the on/off charging cycle continued.
     
    #3 Wxboy73, Jan 3, 2012
  4. HTMLSpinnr

    HTMLSpinnr Super Moderator
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    Normal charging happens with 2 bars on the battery indicator, and will stop with 3 bars. This is dependent on heat and/or AC (electrical) demand.

    I don't have exact SOC values corresponding to each threshold though.
     
    #4 HTMLSpinnr, Jan 3, 2012
  5. macman408

    macman408 Electron Guidance Counselor

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    I've noticed that when the engine is forced on to charge the battery, accelerating can cause the charging to pause for a bit, as it prefers to use engine power directly to propel the car rather than indirectly via the battery. Propelling the vehicle and charging simultaneously could cause the engine to run less efficiently too, so it makes some sense.

    When you don't accelerate for a few seconds, it decides to go back to charging.

    Perhaps this is what you were experiencing?
     
    #5 macman408, Jan 4, 2012
  6. rcshaw777

    rcshaw777 Junior Member

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    I reckon the charging is generated from the rotating wheels rather from the engine itself. If you travel at between 2 to 3 mph, the regenerative energy system is switched off; therefore the power comes mainly from the ICE and does not recharge the battery until the speed hits above 15km/h (9mph).

    I suppose this feature is designed to maintain efficient charge and to extend the battery life.

    If the battery level has reached the lowest point; the ICE will kick in to charge but the engine will be running at inefficient rpm speed (above the normal idle engine speed) to charge the battery and at same time to propel the wheels.
     
    #6 rcshaw777, Jan 4, 2012
  7. Wxboy73

    Wxboy73 New Member

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    Your theory makes sense but I don't know if that's what was happening because I didn't think of that relationship. Now I'll have to try to recreate situation at some point so I can know for sure.

    Thanks for help.
     
    #7 Wxboy73, Jan 4, 2012
  8. qbee42

    qbee42 My other car is a boat

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    You reckon wrongly. Most battery charging is accomplished by the engine spinning MG1, not through regenerative braking (wheel rotation using your terms). In stop and go, the ICE will come on as needed to keep the battery at a reasonable SoC and to keep itself and the catalytic converter hot.

    Tom
     
    #8 qbee42, Jan 4, 2012
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