1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Low charge level ok for overnight(s)?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Priusonamountain, Jun 17, 2015.

  1. Priusonamountain

    Priusonamountain Junior Member

    Joined:
    Jun 17, 2015
    8
    0
    0
    Location:
    Starksboro, VT USA
    Vehicle:
    2005 Prius
    Model:
    Two
    Hi I'm Jon, I'm new to this forum. Yesterday I became the proud owner of a (one-owner, dealer cared- for) 2005 Prius with original batteries, and 178,000 miles. Everything works fine so far, but I wonder if I should be concerned that because I live at the end of a steep half mile stretch of road the battery charge level, by necessity, ends up being below 50% when I get to my house. Does anyone know how the overnight charge level of those batteries affects their longevity? Thanks.
     
  2. Jim Porta

    Jim Porta Junior Member

    Joined:
    Feb 17, 2009
    86
    17
    0
    Location:
    Louisville, KY
    Vehicle:
    2006 Prius
    An uphill grade going to your house is better for the traction battery than an uphill grade coming from your house. Your Gas engine is warm coming home, A cold engine puts most of the traction work on the main battery.
    You're overdue for a 12 volt battery if it is the original.
     
  3. Priusonamountain

    Priusonamountain Junior Member

    Joined:
    Jun 17, 2015
    8
    0
    0
    Location:
    Starksboro, VT USA
    Vehicle:
    2005 Prius
    Model:
    Two
    Good points, thanks. I'll check on the 12 volt. I am used to dealing with an off grid solar home with 6 deep cycle 6 volt lead- acid batteries so I guess my question involves understanding how the traction batteries in the car behave differently from those in my house.
     
  4. The Electric Me

    The Electric Me Go Speed Go!

    Joined:
    May 22, 2009
    9,083
    5,798
    0
    Location:
    Undisclosed Location
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    I don't think it's a concern at all.
    In fact, I've read some posts that suggest turning off the Prius with a lower state of charge on the battery is better than leaving it turned off in a higher state of charge.

    I wouldn't worry about it at all.
     
  5. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    4,215
    1,200
    0
    Location:
    Australia
    Vehicle:
    2005 Prius
    As Jim said, this is probably preferable to the opposite situation of having the uphill to traverse when the engine is cold. When you leave your house you'll have a half mile of downhill to replenish your battery and everything should be good. It does absolutely no harm with nickel chemistry batteries to leave them in a mid level state of charge.
     
  6. Priusonamountain

    Priusonamountain Junior Member

    Joined:
    Jun 17, 2015
    8
    0
    0
    Location:
    Starksboro, VT USA
    Vehicle:
    2005 Prius
    Model:
    Two
    Thanks I'm feeling much better about it now. I loved to see that battery light top out a quarter of the way down the mountain.
     
  7. Priusonamountain

    Priusonamountain Junior Member

    Joined:
    Jun 17, 2015
    8
    0
    0
    Location:
    Starksboro, VT USA
    Vehicle:
    2005 Prius
    Model:
    Two
    Thank you that is very reassuring.
     
  8. Aaron Vitolins

    Aaron Vitolins Senior Member

    Joined:
    Feb 28, 2014
    1,612
    1,144
    0
    Location:
    Franklin TN
    Vehicle:
    Other Hybrid
    Model:
    N/A
    I would also add, if it's hot out side (since you're decending a hill at first) blast ac when you're going down the hill to prevent battery heat in the first place. Also I'd get the hybrid battery cooling fan cleaned since it's at least a decade old.

    Congrats on the new ride! You'll love it! Don't hesitate to ask questions, even if you think they're silly
     
    Priusonamountain likes this.
  9. Priusonamountain

    Priusonamountain Junior Member

    Joined:
    Jun 17, 2015
    8
    0
    0
    Location:
    Starksboro, VT USA
    Vehicle:
    2005 Prius
    Model:
    Two
    Thanks!
    So the battery heats up fast going down, that makes sense, and cleaning the fan..I'll look into that. Blasting the AC is because the intake for the battery cooling is inside the car? Also makes sense if so. Great, thanks for the tips. This is a very friendly and helpful forum!
     
  10. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    4,215
    1,200
    0
    Location:
    Australia
    Vehicle:
    2005 Prius
    Hi Priusonamountain. It's only really significant if the HV battery regularly tops out to the full 8 (green) bars when you're descending.

    In this case you have three options.

    1. Do nothing and let it take care of itself. This is what most people do and the Prius manages the battery charge pretty well. However with an older Prius and a slightly tired battery you may get a bit of overcharge and heating of the cells under these conditions. Mountainous driving conditions are considered to be the hardest case for the Prius.

    You may hear the engine rev loudly as you descend after the battery charge tops out. This is not actually the engine "running" in the traditional sense, it's actually the electric motors dumping excess battery energy by just spinning the engine like a huge air pump (without spark or fuel injection).

    2. If it's really hot then some people use the aircon at full blast on large descents. This actually has two benefits. Firstly it consumes power from the HV battery which can reduce it's peak charge, and also it helps a little to keep it cool as you mentioned.

    3. You can also use "B" mode on the transmission and it applies more engine braking. This can also reduce the peak charge on the battery, though you will probably hear the engine revving even more pronounced than isncase one mentioned above.