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The Great Hybrid Battery Debate

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  • SylviaSylvia Posts: 1,636
    If someone has data they are sharing, let's not attack them. You may not agree with it or believe it, but it doesn't give anyone the right to be rude about it.
  • stevedebistevedebi LAPosts: 4,098
    Every battery powered device I've ever seen carries the warning not to mix battery types, and to replace all the batteries at the same time. So the Prius is different? Maybe, but unlikely.

    This is not to say one CANNOT replace only the bad batteries, but I doubt that the vehicle computers are programmed for this eventuality, since the variables are enormous (one variable in the total output for each battery that is new in an old stack). Most likely there would be some unusual warning messages from the computer, the severity would be based on how many old vs new, how bad the old ones are, etc.

    And I seriously doubt that you will ever get a Toyota engineer to say replacing some batteries in an old pack is acceptable. They will tell you to replace the whole pack...
  • rfruthrfruth Posts: 630
    Hey thats great you've tested the Prius traction battery tell us more can you ?


    And I also doubt that you will ever get anyone at Toyota to say replacing some batteries in an old pack is good enough. They want all the money they can get.
  • john1701ajohn1701a Posts: 1,897
    Then look at it from this perspective:

    It has *ALREADY* been proven that bad modules can completely (and automatically) be ignored without any negative affect on the pack itself. Then rather than multi-state support, you would have new-only support... which is another method of module replacement without the need for the entire pack.

    Now you have two examples to disprove.

    JOHN
  • stevedebistevedebi LAPosts: 4,098
    John,
    I don't doubt that the battery software controls account for gradual depeletion of the battery pack capabilities. If they didn't account for this, they would be idiots, because the packs are going to deplete over time.

    However, that doesn't mean the algorythm accounts for mixed old and new batteries. Maybe it does, maybe it doesn't. But (as was pointed out above), Toyota also would have no reason to want users to be able to replace a single battery, since they would get the return business of a new battery pack.

    The Prius depends on those battery packs. I have no doubt that there is capability to run with some battery modules out, but it is intended as a short term use, until the pack can be fixed. In general, the concept of messing around (in any fashion) with the batteries is unsound in a car that requires electricity to run.
  • gagricegagrice Pahrump, NevadaPosts: 31,367
    Very good point. I remember when radio control cars were the rage. You could change out one cell in the 6 cell battery pack, but it was never able to reach the voltage and current carrying capacity as a full new fresh set that were matched for peak voltage. No two cells are identical so to get a great battery you take the cells that will peak the highest voltage to build a super battery. Those were Nicad not NiMH. They try to tell you that NiMH does not have memory but I can prove otherwise with your laptop computer if it has not gone to the superior Lithium Ion batteries.
  • stevedebistevedebi LAPosts: 4,098
    The laptops and other small applications are different. The NiMh will gradually deplete it's capabilities if it is compeletely discharged. Toyota insists that since the Prius batteries don't fully carge or discharge, they will last for 10's of thousands of cycles.

    Considering the 8 year, 150K warranty, I bet they are correct.
  • gagricegagrice Pahrump, NevadaPosts: 31,367
    I wonder if they willingly put out that warranty, or were they coerced by CA regulators? I know with lead acid car batteries you can almost bet they will die the week after the warranty expires.
  • gagricegagrice Pahrump, NevadaPosts: 31,367
    On battery life expectancy: NOTHING with batteries that consumers own has an 8-year battery life.
    This was part of the debate that forced Toyota to warranty the Hybrid batteries for 8 years 150k miles. You may find it interesting as I did. This has been my skepticism from the start. Although with 8 years and 150k miles I would not fret over buying a hybrid.

    http://solstice.crest.org/discussion/ev/current/msg00392.html
  • rfruthrfruth Posts: 630
    Of corse nothing manages the batteries like a hybrid or costs like one either. Maybe if a cordless phone was $ 500.00 the battery would be managed better heck some $ 200.00 bicycle lightning systems that use Ni-MH batteries come with dumb chargers (they don't check the temp of the battery or for any existing charge, plug it in and the charger goes full tilt boogie even if it means cooking the battery) - but as you know auto manufacturers would offer zero warranty if they could, why risk warranty claims, for return business ?
  • gagricegagrice Pahrump, NevadaPosts: 31,367
    If I put 150k on a vehicle in under 8 years I would have no problem buying a Hybrid. Just get rid of it before the warranty is up. If batteries don't get hot in the charging stage and are not let go all the way down, they should last a good long time. I have a Dell Inspiron 7000 that is 5 years old and the battery is still good. I have a one year old Inspiron 4100 that won't run 15 minutes on the battery.
  • gagricegagrice Pahrump, NevadaPosts: 31,367
    On dumb chargers. I just changed the battery in a year old Panasonic cordless. It was Nicad and one cell would not hold a charge for more than a few minutes.
  • john1701ajohn1701a Posts: 1,897
    Poor charge management is why most rechargable batteries suffer shortened life.

    If your cell-phone shutdown at 40% and refused to power back up until you plugged it in, the battery would last dramatically longer. But instead, users drain the thing to totally dead on a regular basis. That's a huge difference from the way a system like HSD in Prius works.

    JOHN
  • john1701ajohn1701a Posts: 1,897
    NiCd rechargable batteries were inherently problematic. They suffered from memory-effect, were environmentally dangerous, and they could hold not as much power as NiMH. That's why NiCd is considered long outdated technology.

    JOHN
  • john1701ajohn1701a Posts: 1,897
    Another common hybrid battery misconception is that all the electricity feeding the motor comes from the battery-pack.

    While that is true for a "mild" hybrid, it is not for a "full" hybrid like Prius. In fact, 100% of the time the engine is providing thrust to the wheels it is also powering the generator-motor. The resulting electricity is immediately used by the thrust-motor.

    Preventing the battery-pack from being used as much obviously helps to extend the life of it.

    JOHN
  • gagricegagrice Pahrump, NevadaPosts: 31,367
    Question, I read an article that says the hybrid batteries are only charged by the regenerative action of slowing and braking. The writer said this caused problems on long uphill grades on a cross country test run. Is that true?
  • Becareful when someone use a general word "hybrid" since not all design were created equal. HSD can split power from ICE to generate electricity while climbing hills, assuming the hill is not steep enough to have spare power from the ICE.

    04 Prius battery ECU will not let the battery discharge below 40% SOC. The rest of 60% of the 1.31 kWH battery can provide 28 hp for 135 seconds. If you climb the hill at 60mph and the hill is so steep that the battery provides all 28hp for 135 seconds, Prius can trouble 2.25 miles before the battery SOC get to 40%. It is when the turtle icon appears.

    If the hill is not as steep and Prius main ECU request only 14hp from the battery, Prius can go up 4.5 mile long hill. That's a very long hill!

    I know you had bad experience with batteries. Let me give you another graph which shows the Cylinder D-shape batteries(Used in Japanese Prius) and Prismatic batteries(Used in US Classic Prius). They tested over 180,000 miles for Cylinder and 150,000 miles for Prismatic. Note that 04 Prius batteries has less Internal Resistence than last generation Prismatic modules. Basically, these batteries can keep going and going and going .....

    image

    Dennis
  • gagricegagrice Pahrump, NevadaPosts: 31,367
    That makes sense and goes along with what the writer was saying about the Prius. They were in the Rockies and he was trying to pass on a long uphill stretch. He could not feel the electric motor kicking in. He probably already discharged to the 40% level. So it was just the ICE which was not enough power to go around. I am not sure how fast he was going. I can't find the article now. I doubt it is that important. I am sure that the hybrid has forced vast improvements in battery technology. The last of the electric cars were also instrumental in improving NiMH batteries. I hope they are as long lived as Toyota is predicting. Thanks Dennis
  • stevedebistevedebi LAPosts: 4,098
    No, the Prius doesn't push the envelope in battery technology; it just makes sure the batteries don't get over charged or fully depleted. Nothing new there.

    It uses the plain old batteries, several years old technology...
  • john1701ajohn1701a Posts: 1,897
    Actually, it depends what you mean by "technology".

    The NiMH itself within the Prius battery-pack is record-breaking "technology". The energy-density is significantly higher than just "plain old batteries". Other NiMH simply cannot compare.

    JOHN
  • stevedebistevedebi LAPosts: 4,098
    OK, please tell us how the Prius HiMH is different technology from "regular" NiMh....

    Do you have data to back up your "energy density" statement?
  • john1701ajohn1701a Posts: 1,897
    Just look at Toyota's press releases from exactly 1 year ago. You'll find documentation about that battery break-thru there.

    JOHN
  • john1701ajohn1701a Posts: 1,897
    Also, the proof is rather obvious.

    The battery-pack was reduced by 11 modules (from 39 to 28) with the 2004, yet it now delivers even more power than the 2003.

    JOHN
  • "No, the Prius doesn't push the envelope in battery technology; it just makes sure the batteries don't get over charged or fully depleted. Nothing new there."

    Some hybrids like Civic Hybrid and Escape Hybrid are still using Cylindrical D-shape NiMH batteries. The graph I posted above shows that Internal Resistance is very high compare to the first generation of Prismatic NiMH. Second generation Prismatic used in 04 Prius is a couple of generation ahead of cylindrical model. See the inner working of both types and you might want to rethink about your "Nothing new there" comment.

    image

    This following information is for the first generation of Prismatic NiMH used in the classic Prius; from The Society of Automotive Engineers, written by Electric & Hybrid Vehicle Engineering Div. of Toyota Motor Corporation.

    "The case is made of plastic, which was selected based on its resistance to the alkaline electrolyte, electrical insulation between cells, formability of the modular shape, weight, etc. The rectangular modules, when combined into a battery pack, reduced dead space and require a minimum amount of space for cooling. Thus, a compact package has been realized."

    "To ensure electrical safety, the component parts of the high-voltage system are enclosed in the battery pack, ..... These parts consist of a system main relay (SMR) with a built-in current sensor, a service plug with a built-in fuse, and a battery electronic control unit (ECU)."

    "It(SMR) functions(cuts off the high-voltage system) similarly when the vehicle is involved in a collision or when there is a malfunction in the system."

    "The current sensor is used for calculating the state of charge (SOC) of the battery. "

    "The fuse prevents electric shocks and fire in the vehicle when the battery short-circuits, such as in the case of a collision."

    "Based on the current, voltage, and the temperature of the battery, the battery ECU calculates the SOC and transmits it to the vehicle control system. It also monitors the battery for abnormalities."


    Information from Panasonic about 2nd gen Prismatic NiMH used in 04 Prius:

    "High power battery module for HEV application (30% more power than conventional prismatic battery)

    Newly developed battery has high power of 1300W/kg, 1.3 times higher than our conventional prismatic battery, and energy density of 46Wh/kg. By adopting new electrode materials and newly developed cell connection structure, internal resistance could be reduced, and more higher reliabilities on likely long life characteristic are improved due to the improvements of cell stack construction etc."


    Dennis
  • "OK, please tell us how the Prius HiMH is different technology from "regular" NiMh...."

    I'll point you to Panasonic website that have all the information that you'll need.

    See which hybrid used which type of NiMH:
    http://www.peve.panasonic.co.jp/e_news.html

    See spec of 1st gen and 2nd gen prismatic NiMH:
    http://www.peve.panasonic.co.jp/catalog/e_kaku.html

    Spec of Cylindrical NiMH:
    http://www.peve.panasonic.co.jp/catalog/e_maru.html

    Battery catalog page with more links:
    http://www.peve.panasonic.co.jp/e_catalog1.html

    Dennis
  • gagricegagrice Pahrump, NevadaPosts: 31,367
    Good information and in English, Thanks Dennis, Gary
  • stevedebistevedebi LAPosts: 4,098
    Well, I stand corrected. Thanks for the updates...

    Very useful to have these boards...
  • larsblarsb Posts: 8,204
    quote MidCow:-"The current fear is the unknown life-span of the traction batteries."-end quote

    Lots of good points MidCow, you have a good grasp of the situation. Leading to a "BUT:"

    I'm not sure where you might be getting the indications of this being an actual FEAR that might be preventing Hybrid purchases...?....?...?

    So far we have true stories of Priuses going 150K miles and being bought back by Toyota for evaluation...

    We have 1997 model year Priuses on the road in Japan...

    We have warranties of 8 yr/100,000 miles on the batteries in some hybrids....

    Is there ANYWHERE a story of ONE SINGLE potential Hybrid buyer telling the salesperson, "Well, I love everything about the car, but that darn uncertainty about the life of the battery is just KILLING the deal !!"

    I don't think we have any of that. Even if we DO have a few isloated incidences of that happening, I cannot for a second believe that it has ANYTHING AT ALL to do with the acceptance of Hybrids to the mainstream buyer...

    Anyone have any evidence to support that fear?
  • I'm not sure where you might be getting the indications of this being an actual FEAR that might be preventing Hybrid purchases...?....?...?

    Here's an indication.
    I cannot even consider hybrids until the battery life-span has been well proven in the real-world

    So far we have true stories of Priuses going 150K miles and being bought back by Toyota for evaluation...

    And this is supposed to make a sceptic feel comfortable ? What it makes me feel is that Toyota is surprised that the car made it to 150K miles, so they want to evaluate it. Causes one more concern about the product, rather than the other way around.

    Is there ANYWHERE a story of ONE SINGLE potential Hybrid buyer telling the salesperson, "Well, I love everything about the car, but that darn uncertainty about the life of the battery is just KILLING the deal !!"

    Fortunately there's no need for such a story. People actually know how they feel about hybrids so there's no need to go a salesman and tell him that story.

    Anyone have any evidence to support that fear?


    Is there enough evidence NOT to have that fear. Maybe in your mind there is, but certainly not in mine.
  • gagricegagrice Pahrump, NevadaPosts: 31,367
    What it makes me feel is that Toyota is surprised that the car made it to 150K miles, so they want to evaluate it. Causes one more concern about the product, rather than the other way around.

    I think the only safe place to own a Prius is in CA. With the 150k mile mandate on emissions, Toyota has to stand behind the car and all parts that could keep it from being an AT=PZEV rated car. I still wonder if the state would come to your rescue if the car crapped out after a 125k miles....
This discussion has been closed.