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Question About Battery Health

Discussion in 'Gen 2 Prius Main Forum' started by prius_power, Oct 29, 2018.

  1. prius_power

    prius_power Junior Member

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    I had a friend in my car while I was driving, and he noticed that the car stays in the green for the majority of the drive (including hitting full green bars in city driving). He works on Prii and said that the battery may be on its way out. Not a big deal if it is, I have spare cells. But I also noticed that the battery doesn't discharge overnight like most weak batteries, but can drop to one purple bar when starting the drive (from green or full blue charge) or will randomly plummet to two purple bars quickly during a drive, but usually only once, and then it's fine again. I told him this again, and he said it could also be an inaccurate MFD. What say you guys? Weak battery, inaccurate display, something else?
    Thanks!
     
  2. davecook89t

    davecook89t Senior Member

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    The battery is certainly weaker than when it was new, but as long as you are not seeing warnings on the dash and the MFD, and getting decent MPG, does it really matter? It will keep doing its thing until the modules come out of balance. I would definitely not touch the battery until you start getting warnings. Once you start replacing modules, you will find yourself in a never ending game of trying to balance the new ones against the ones you already have, that is unless you invest in one of the Prolong battery reconditioning systems that @jeff652 sells. Whether you decide to do that, I would think, depends on the number of miles you have on the car already and how long you plan to keep it.

    The MFD's display for State of Charge has rarely, if ever, been proven wrong to the best of my knowledge, but be aware that at its minimum value it shows an SOC of 40% of battery capacity and and its maximum it shows an SOC of 80%. Those percentages are based on current battery capacity, however, which is probably much less than it was when the battery was new.
     
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  3. bisco

    bisco cookie crumbler

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    i agree with your friend. might not be too late for reconditioning, i'm not sure.
     
  4. 05PreeUs

    05PreeUs Senior Member

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    I don't know, generally when a NiMh starts to wear out, they lose capacity before voltage causing the dreaded yo-yo of the charge bars from green to pink and back every few minutes as the rate & frequency of dis/charge increases. The OP does not report that concern, suggesting that this may be a normal condition given the specific drive cycle.

    In any event, if it is the production HV pack, the time is limited on it.
     
  5. prius_power

    prius_power Junior Member

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    Thanks all for the responses! I definitely wasn't going to touch the battery until it throws codes. The only concern was that I have a few long drives this month and also drive for work. I don't want to have to get the car towed back home. If I can drive it with warning lights, I would do that.
     
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  6. PriusCamper

    PriusCamper Senior Member

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    Nothing to worry about yet... Time to think about buying some hybrid battery preventative maintenance gear or buy servicing from someone who uses the gear. In the meantime taking it on some long drives is the best driving you can do for the health of the battery pack.

    Driving it around in lots of traffic/gridlock is the worst think you can do for the pack... Other thing is heat... Batteries usually fail up above 100' degrees in temp. So don't park your car with all the windows rolled up in full sun all day and then jump in and drive it in bad traffic. Keep interior of car cool as much as feasible.

    Primary issue with these NiMH batteries is they crystalize and lose capacity and need to be periodically re-conditioned tho break up the crystals and maintain capacity. But rather than making this maintenance part of the Toyota vehicle service plan, they decided to simply make it so the car continues to function normally even after the battery pack loses more than 50% of its capacity.

    So what you friend is saying about battery being on its way out, is same thing as saying your battery is losing its capacity to the point it might turn into a problem, which is evidence by how rapidly the display changes from full charge to lower charge. If you spent $2K on a new pack your MPG would improve and the display would show a very slow change from full charge to lower charge.

    Once you're done with your trip, you could get several more years out of that pack with some annual battery conditioning service via the closest mechanic with Prolong conditioning gear, which in your case would be Tampa Hybrids or Royalty Auto in St. Mary's GA.. Or take it a simple DIY direction and buy your own gear so it's less hassle and less expensive. Learn more about how all this works and your options here: FAQ

    Essentially it comes down to this: you can spend hundreds now in preventative maintenance and substantially extend the life of the pack, or you can spend near a thousand dollars on labor costs for rebuilding the pack, or buying a rebuilt pack for a year or two or three of life after it goes bad, or spend a couple thousand on a new battery pack and never think about it again for the rest of the life of the vehicle. What you can afford will define how you approach this...

    And again if you drive lots of highway miles you're pack is gonna be way better off and longer lasting than if you driving in traffic in a city and let it bake in parking lots with the windows fully rolled up.
     
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  7. davecook89t

    davecook89t Senior Member

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    Our Gen 2 has 267k miles on its original battery. It had 211k when I bought it. That did not prevent me from driving it from Vancouver, BC to NYC right after I bought it, then back out to the West Coast the following summer and back to NYC a month or so later. I have also taken it from New York to Florida and back several times and am planning to take it again to Florida in a week or so. When I drive to Florida and back, I usually have my wife and her mother with me. I have not seen any warning lights yet, but expect I will before too long. I'm not sure what we will do when that happens. With as many miles as it has, I probably will not spend any money on it to repair it, but would hope to get it to our destination, wherever that might be. I believe I will have a few hundred miles of sluggish performance after the lights first appear. If I do not think we'll be able to make it to where we are going, I will probably leave the Gen 2 at the nearest salvage yard and come back to get the Gen 4 which has been sitting in our driveway ever since I bought it a year ago. Hopefully, my wife and mother-in-law won't mind waiting by the side of the road until I get back.;)
     
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