50Wh regeneration?

Discussion in 'Gen 2 Prius Main Forum' started by firefite, Dec 12, 2018.

  1. firefite

    firefite Junior Member

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    When I drive my 206 Prius it shows 50Wh all the time some time 3 to a row? does that mean that the big battery is going bad. It didn't always show that much regeneration, It just started showing that about a year ago. always before that it would show 50Wh one in a while?
    Thanks for any help. Firefite
     
  2. Skibob

    Skibob Senior Member

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    Have you changed where you drive or is there more traffic? The regen is based on how much you take your foot off the gas or use the brake.
     
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  3. bisco

    bisco cookie crumbler

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    Not that I recall reading. How many miles on her?
     
  4. PriusCamper

    PriusCamper Senior Member

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    As your battery pack ages it will lose capacity... Toyota designed the pack to still work normally even at a 50% loss of capacity... The sign of declining capacity is a more rapid charge and discharge rate, so I'm pretty sure this is what you're experiencing. This problem of capacity loss is the nature of metal-based batteries, which along with being super heavy is why EV vehicles are now focused on lighter Lithium-based batteries that don't lose capacity in the same way.

    To restore capacity in your battery you need to go through a process of reconditioning, which essentially means deep discharging and recharging to re-active stagnant poorly conducting areas of the electrolyte in the pack. Hybrid Automotive sells a harness, discharger and charger so you can do this work on your car without removing the pack. But if you want to maximize the life of your pack even more, discharging and recharging each of the 28 modules in the pack individually is more effective, as well as the way to find bad modules before they get bad enough to throw a warning light.

    If you want to learn more about how to do this, let us know and we'll walk you through it... In the meantime here's a more thorough explanation of what's going on inside your battery pack: BU-807: How to Restore Nickel-based Batteries – Battery University
     
    #4 PriusCamper, Dec 13, 2018
    Last edited: Dec 13, 2018
  5. fuzzy1

    fuzzy1 Senior Member

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    But shouldn't an aging battery show up here only as a more rapid rise of the battery SOC gauge?

    Those 50Wh symbols ought to come only from the actual amount of energy regenerated from braking, not from changes to the battery capacity itself. That would suggest a change in driving pattern or route or style, such as the driver making better use of regen.
     
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  6. PriusCamper

    PriusCamper Senior Member

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    Yes, you're correct in some ways...

    But an old battery pack at only 50% capacity will discharge much more rapidly both when in use, and via self-discharge, which you will often see on here as people who's really old low capacity pack is only at two bars when they start the car in morning.

    So you will see more 50wh icons first thing in the morning in those cases... Whereas in a new or reconditioned pack, the SOC doesn't fluctuate as much and the car doesn't have to put as much energy back into the pack.
     
  7. Skibob

    Skibob Senior Member

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    I still get the little 50wh cars even if my battery is charging to the green
     
  8. jerrymildred

    jerrymildred Senior Member

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    The state of charge changing more quickly in older batteries due to loss of capacity is because state of charge is a percentage. It doesn't mean that it gobbles up or spits out electrons faster, just that it doesn't take as many electrons to fill or empty it. 50 kWH is 50 kWh whether the battery can hold 4,400 kWh or only 2,000.

    An increase of 50kWh icons is due solely to an increase in the amount of electrons per minute put back into the battery. It's an absolute number, not a ratio like SOC.
     
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  9. fuzzy1

    fuzzy1 Senior Member

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    Agreed so far ...
    Say what??? :confused:

    The amount of energy that car can recapture through regeneration, has no connection to the remaining battery capacity. Other than it won't regenerate when there is no room remaining to put it into the battery.
     
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  10. Skibob

    Skibob Senior Member

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    Exactly. My guess is he is using his brakes more for some reason. The OP states it started about a year ago. I wonder if he moved or changed jobs around that time?
     
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  11. Skibob

    Skibob Senior Member

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    I have had that happen. One time when going down a long hill the battery icon filled to the top, stayed that way for a little while, then the arrows just turned off. I could swear I heard the engine speed up but I’m not 100% sure.
     
  12. fuzzy1

    fuzzy1 Senior Member

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    For those of us traveling in or through the mountains, this is a very regular occurrence. Yes, the engine does spin up for engine braking, a little bit if in D, a whole lot if in B.
     
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  13. PriusCamper

    PriusCamper Senior Member

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    Yes, but beyond just loss of capacity in old batteries, the self-discharge problems with an old battery that starts up in the morning at only 2 bars even though it was in the green the night before, as well as other symptoms like sudden SOC drop from all green to two bars in less than a mile is going to cause the inverter & regenerative breaking to produce 50wh hour icons to appear more often than with a newer, healthier battery that is stable and not starting to fail.
     
  14. fuzzy1

    fuzzy1 Senior Member

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    How so?

    All that battery degradation will cause the engine and MG1 to work harder to produce energy to recharge the battery. But this path doesn't create any of those regen icons.

    Those icons come only from the regen path, including both manual braking and from the no-gas-pedal synthetic light drag to simulate typical non-hybrid engine drag.. (Also from B-mode and cruise control regen braking.) In normal conditions with a good battery at its normal 6 bars, or less, the car isn't passing up any regen opportunities. Lowering the SOC gauge below that doesn't create any more regen opportunity.

    The only time a failing battery should create more regen opportunity is when self-discharge drops it from full prematurely. But such cases should be more than offset by the times it fills up too quickly from degraded capacity, thus throwing away energy that a healthy battery could have harvested. These cases should create fewer of those icons, not more.
     
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  15. ChapmanF

    ChapmanF Senior Member

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    Self-discharge the one idea there that could serve as a potential explanation of more 50Wh badges, and even so, to show that it is any significant part of the story would take instruments, measurements, and math. Higher SOC lability is out of the running as an explanation, as Jerry explained in #8, because it just reflects a loss of capacity in the battery, not a change in how much energy 50Wh represents.
     
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  16. PriusCamper

    PriusCamper Senior Member

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    Thanks for the reminder we're talking about regen only... Another key reminder is that when OP's only reported symptoms is: "It didn't always show that" and "It just started showing that about a year ago." we're just getting started on what could be wrong even though by all signs other than this there's nothing wrong.

    But Fuzzy1 & Chapman for sure have me thinking beyond the battery asking for more of a charge because of rapid voltage drops in old batteries about to fail. So, trying to think of a scenario where regen would be happening more often than normal?

    I guess that would be diagnosed by 1) seeing if the circuit path that controls the amount of energy MG1 generates is behaving normally and 2) if the car has excessive drag when MG1 is being used?
     
    #16 PriusCamper, Dec 13, 2018
    Last edited: Dec 13, 2018
  17. jerrymildred

    jerrymildred Senior Member

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    So, anyway, @firefite, if we haven't made you run off into the night screaming, after a little over-thinking by one of our members, it boils down to this. From the information you provided, it looks like you're getting more 50kWh icons because you're decelerating more -- either by coasting or braking. It may also be that you're braking smarter by being gentle and using less friction brake and more regeneration brake.
     
    #17 jerrymildred, Dec 14, 2018
    Last edited: Dec 14, 2018
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  18. James1964

    James1964 Member

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    Posted via the PriusChat mobile app.
     
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  19. James1964

    James1964 Member

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  20. jerrymildred

    jerrymildred Senior Member

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    I remember seeing this several years ago. I'll have to find time to watch it again. As I recall, it was very good. Thanks for getting it in front of us again.
     
    #20 jerrymildred, Dec 15, 2018
    Last edited: Dec 15, 2018
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