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Hybrid battery balancing

Discussion in 'Gen 2 Prius Technical Discussion' started by Jonscheets, Sep 26, 2017.

  1. jeff_the_computer_guy

    jeff_the_computer_guy Junior Member

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    BTW, kudos to TMR-JWAP for the 2a, airflow, set and forget model (among other things). Made it much easier and more consistent as a process. I'll give full credits later but lots of good experience there.
     
  2. jeff_the_computer_guy

    jeff_the_computer_guy Junior Member

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    NiMH DISCHARGE 1.5A 5.8V

    oops, you did show that value. I have no idea on the immediate delay then....
     
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  3. vvillovv

    vvillovv Senior Member

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    @gabrielcraft.me
    and keep a fan on any modules during charge and discharge, 'especially' if not monitoring module temps continuously while cycling.
     
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  4. DanielR

    DanielR New Member

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    New member here!

    I just finished much of this process, and just wanted to thank everyone here for their helpful information! It was so comforting to finally find a place where many of my questions were already answered, and all I had to do was UTFS. Forums like this remind of me a wonderful time when this was all we had on the internet…

    Kudos again to everyone.

    If you’re doing this process with a CQ3, and you’ve made it this far in the post, everything you really need to know is contained in this and a couple other posts.
     
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  5. C Wagner

    C Wagner Member

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    Just checking in...my Gen 2 with 166K is now at 186K. I did the pack rebuilt/refurbish in Nov 2020 and it's just passed 3 years later - battery still testing 'good' with Dr Prius longevity test. You can do it!
     
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  6. DanielR

    DanielR New Member

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    I had a weak block #8, and sure enough, modules 15 & 16 were giving around 800-1000mAh discharges, even on 10+ cycles. However…

    I also had about 3 others that wouldn’t clear 1,500mAh. I replaced them with modules from a reputable eBay seller, which tested at about 5,850mAh discharge on full 3 cycles. The rest I was able to bring back to 4,500mAh and up.

    The settings I used were 1.2A discharge to 5.5V and 2.2A charge to Delta Peak Sensitivity of 20mV/cell. I know that we aren’t supposed to go below 6.0V, but these modules were going to be replaced otherwise, so I decided to just go for it— and, I’m glad I did!

    Thanks again to everyone here, whose older advice still helped in Dec, 2023! I hope to get another couple years out of it before I have to do it again!

    The biggest thing that I learned was not to use cheap, Walmart leads, but rather make your own! I used 18AWG high-quality wire and soldered good banana plugs and alligator clips to it. The Walmart leads gave me erratic readings, and eventually started to fuse together, wherever two wires were bumping into each other on the way back to the charger. It’s like they melted, but they never felt warm.
     
  7. Spradilak

    Spradilak New Member

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    Hey glad to see these posts helped you aswell! I just started this process a couple days ago..the car has 201k on what I believe is the original battery. Unfortunately mine appeared to be leaking from 1 or more modules as seen in my recent post.

    I was wondering what year and mileage your car is and if it is the original battery. Your numbers(mAh)are much higher than mine, so I was just curious. My highest discharge thus far is 4004 mAh the lowest is 2014 mAh and the average is probably about 2500 mAh, though I'm still cycling some modules. How many cycles did you end up doing for the modules you got back up to 4500 mAh?
     
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  8. R-P

    R-P Active Member

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    Seconded.
    Here's my 55Ah AGM battery to replace my 38Ah original Prius battery. Straight out of the box.
    [​IMG]

    Let's test it. Oh crap, that's not good, they send me a dud!!! Voltage drops to half with a mere 55W load. Gotta complain to the company that shipped it!
    [​IMG]

    Oh nevermind... The chinese 16AWG wire is actually a poorly soldered 24AWG headphone lead...
    [​IMG]
     
  9. Erc32

    Erc32 New Member

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    Man where can I find a Toyota battery installed for 2k I live in NJ I can buy the battery from the dealer for $1950 before tax but just dreading installing it it's freezing outside and I don't have a garage
     
  10. mr_guy_mann

    mr_guy_mann Senior Member

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  11. DanielR

    DanielR New Member

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    I have a 2010 Prius III with Solar Moonroof and JBL/NAV. It was at 190,000 when I did this.

    I have learned a LOT since making this post, though. I’ve also managed pick up about 30 spare modules (donations from other members) which are all discharging at 5,500mAh and higher. A couple of them are over 6,000mAh! The reason they were given to me is because I’ve started fixing these Prius traction batteries for people for free, as a local service in my community for those who cannot afford the repairs. They bring their entire pack to me, and I only ask them to buy their own replacement modules from eBay, and I’ll handle the rest. What I hope to do eventually is also repair for the people who can afford it, and ask them for a donation to keep things going.

    Back to the modules— I’ve learned that you can actually discharge these modules to much lower than 6.0V. I am now experimenting with discharging to as low as 3.0V, in an attempt to revive those ones that wouldn’t break 4,000mAh when discharging to 6.0V.

    I have a post about it in the DIY Prius FB group, but I will probably also post about it here eventually.
     
  12. dolj

    dolj Senior Member

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    I, too, have had good results going down as low as 0.5 V per cell (i.e. 3.0 v per module) as well but you must charge up the module to 6.0 V before you start measuring the mAh put into the module. Otherwise, the mAh put in will, logically, be overstated. You probably know this already, but I thought it wouldn't hurt to restate it for those who haven't thought about it.

    Going to this depth of discharge probably only yields noticeable results the first time (in 10 years) as it seems to make no appreciable difference if you state the repeat dischg/chg cycling regularly like once every year or two.
     
  13. Carall

    Carall Member

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    Discharge that whole pack to 3 volts, about 0.10v per module. That all you can do to that battery pack if it's still any good.

    Discharging below 5v the capacity reaches over 8000mAh, but after using the battery in a car it drops a little. If the battery is bad (usually dry), the capacity drops by 2 times or more. The voltage test at 40% shows how strong the battery is.
     
  14. dolj

    dolj Senior Member

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    How do you get 8 Ah out of an old pack that is originally rated at 6.5 Ah?

    You need to start counting the capacitity from 6 V otherwise you're just fooling yourself.
     
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  15. Carall

    Carall Member

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    I described the method several times before how I get 8000mAh. Capacity returns to normal, drops after a short period of use.

    7.2 volts is the voltage of a discharged module (1.2 volts per cell). ~8.4 volts is voltage of a charged module (1.4 volts per cell). Capacity is measured in this range, in which the Prius operates.
     
  16. Xeico

    Xeico New Member

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    Some info about one module:
    Manufacturer: Panasonic EV Energy
    Battery Type: Nickel Metal Hydride
    Rated Capacity: 6.5 Ahr (C/3 Rate)
    Number of Cells: 6
    Maximum Cell Charge Voltage: 1.5 V
    Minimum Cell Discharge Voltage: 1.0 V
    Nominal Cell Voltage: 1.2 V

    Discharging below 6V can damage the module.
     
  17. Carall

    Carall Member

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    How exactly?
     
  18. jdenenberg

    jdenenberg EE Professor

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    Each module has 6 1.2v NiMh battery cells in series and the module voltage is the sum of the 6 cell voltages. If the module is out of balance (different state of charge on each cell), it is possible for the weakest cell to be reversed (voltage drops below zero) when the module is excessively discharged. Reversing a cell causes permanent destruction of that cell.

    As you get the module into a balanced condition, it becomes safer to reduce the module voltage lower than 6 volts, but always be careful to do the last bit of discharge at a low current.

    JeffD
     
  19. Carall

    Carall Member

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    I have known this intimidation for a long time, but during the reconditioning process this does not happen. Recently I discharged the entire battery pack to 0.4 volts and there was no polarity reversal. I have 4 batteries that need to be junked. Polarity reversal occurs when a module self-discharges and this does not happen after a day but much later.
     
  20. jdenenberg

    jdenenberg EE Professor

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    Do what you want, but if two of the cells were 0.1 volt lower than the other 4, going down to 0.4 volts is likely to reverse one of the weaker cells. You can go that low once the cells in a module are reasonably balanced. You were lucky that those modules were not out of balance.

    I had a single cell reversal while driving my 2004 Prius in 2009 (at 195k miles) and that started me on learning how to rebalance these batteries.

    JeffD