Air flow around Hybrid battery pack.

Discussion in 'Gen 3 Prius Technical Discussion' started by Old Wrench It, Apr 8, 2018.

  1. Old Wrench It

    Old Wrench It New Member

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    In observing the differences in temperatures where the middle and end of the battery pack are always significantly higher then the front end where the air Flows In it doesn't seem like a very efficient design as it is. It seems to me that the metal casing is relied upon as the exit of thermal Heat which particularly when it's hot out does not seem a very efficient means at all. Am I missing something with the exit of heat from the battery pack? Looking at it it seems fairly simple to add in a top vent that leads to one of the rear side vents powered with an old computer fan. Somehow that hot air needs to be released more efficiently. Has anybody worked with this idea? I noticed Lexus Hybrid has a release vent that runs on the bottom 2 the back right passenger side vent.
     
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  2. bisco

    bisco cookie crumbler

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    it's the cheapest way to get the majority of packs beyond warranty. certainly, more efficient cooling will help.
     
  3. Raytheeagle

    Raytheeagle Senior Member

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    The vent exit is on the top of the battery, which seems appropriate as warm air rises ;).

    The ECU manages the fan speed based on the temperature, and for our 2010, I haven’t found an issue with its operating modes. There are 6 speeds for the fan, and it is rare for it to get above 3, in my experience :).

    What are you seeing that you would like to be different?
     
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  4. Old Wrench It

    Old Wrench It New Member

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    The only venting I see is the black soft tubing for venting potential gas discharges from each module - think that was only on for a few years. From Hybrid Assistant
    "HV Battery has multiple sensors: usually the inner ones are higher that the outer ones. % Max shows time percentage the specified sensor was the highest of the pack." On mine the outer sensors are always higher, usually the last one is highest, but sometimes the middle is highest. Haven't really tested it on a hot day, last test recorded of temps was end of January
    upload_2018-4-8_21-6-29.png
     
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  5. bisco

    bisco cookie crumbler

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    there should be a vent exhaust running over and out through the right rear quarter panel.
     
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  6. fotomoto

    fotomoto Senior Member

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    Adding a computer fan to the top/middle portion of the pack could possibly work well but I think one would run into floor loading issues that could crush the fan assembly. For example, a home store worker loaded (tossed) 150 lbs of sand bags into mine this weekend.

    A somewhat easy and no cost option for the DIY type could be to remove and disassemble the pack and shuffle the middle modules to the sides so they get a "rest" with more cooling. It's known among the rebuilder community that the middle modules are typically the first to fail.
     
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  7. Lucifer

    Lucifer Active Member

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    Love to buy an aftermarket liquid cooling kit for the traction battery, similar to a computer aftermarket cooling kit, it would be better if Toyota would incorporate one.
     
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  8. Old Wrench It

    Old Wrench It New Member

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    In the 2010 it only dumps exhaust air into trunk area above spare tire.
     
  9. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    I have a theory on this...

    The design of the battery modules themselves is actually really cool. (Pun intended :p) With the metal surface, the heat should collect there. Then with the bubbles and sphere cavities it creates tiny air channels down the sides of each module. I can imagine this now as a team of Japanese engineers modeled this in 1995 or 1996 3D CAD programs of the day for the 2001 "Gen1" release.

    If you take those 28 modules and completely seal them, air tight, from the top to the bottom, and then place that in a sealed environment with forced air, you will force the air to sweep over each module evenly because of the pressure and shape.

    If you look at the design of the battery pack vents, there is a top and bottom.

    Now I imagine in 1996 when this team of Engineers presented their ideal design to Toyota Manufacturing about a multiple zoned pressurized battery compartment with air tight seals to the outside plus a higher power fan to force air through the plenums, it was struck down. Too expensive to manufacture, too complex, whatever. The pack became bigger but required no seals. They kept the placement of the top and bottom vents, design of the modules, etc. But now the air just blew from the bottom went up and was sucked out. The problem though is that the air just goes around the "brick" of 28 modules and not through the nicely crafted little air channels on the batteries.

    All of this is just my guess. But I have spent a lot of time looking at the battery pack design, and it doesn't make any sense the way it is without two conflicting ideologies and my guess is ideal Japanese engineering perfection and the accounting departments.
     
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  10. Old Wrench It

    Old Wrench It New Member

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    Lol...nice theory, makes some sense...it does make me wonder if thermo dynamics engineers worked on it intially.
    There is a strange balance to building heat and air flow when things are burning and also getting things hot enough to burn. The fins and compression force of metal sides are a great design, they would in a passive air flow probably evenly disburse heat and increased pressures. I think numbers 6 and 10 are most common failed modules due to having 2 different pressure loads, the air flow typically does not cool middle packs as well, 6 and 10 are same placement from ends, middle packs get significantly hotter making for greater internal pressure, 6 and 10 constantly are handling two different pressures - now there's a psychology joke here somewhere, but I lost my charge.
     
  11. Old Wrench It

    Old Wrench It New Member

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    added an extra heat release tube which seemed to have a good effect. Beginning intake was 67 f, ending was 71. Beginning batt temp was 85 f, then 87 quickly, but came down to 82 f at end. Don't think the fan even came on. This was on a little over 4 miles drive
     
  12. Old Wrench It

    Old Wrench It New Member

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    Battery pack is definitely staying cooler with even temps across, the mid sensor usually 1 to 2 degrees F cooler.
     
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  13. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    which is evidence in favour of the plenum design being ineffective as executed
     
  14. mjoo

    mjoo Active Member

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    Do you have a picture?
     
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  15. Old Wrench It

    Old Wrench It New Member

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    Screenshot_20180416-190732.png
     
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  16. Old Wrench It

    Old Wrench It New Member

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    Will be swapping out one more module this coming weekend. Will take some pics of my heat release tubing then. I think the original design implemented fails to deal with basic thermal dynamics, as soon as the forced air intake hits higher temp it will rise if possible as well as tending to flow in spaces between batteries that are designed to encourage flow. So much of the forced air immediately rises and exits making for a consistently cooler area that hot air which usually rises is supposed to make it's way pass. Hot air somewhat pressurized against more pressurized, by fan force, cold air. On the other end the remaining forced air flows around batteries but probably circulates back down through pack when meeting significantly hotter air. My Pac used to be consistently 10 to 15 degrees hotter in center when running hot. With it stabilized I see the Prius computer changing resistances and consistently balancing the 14 module packs. Even though I suspect #3 has a needed replacement...sometimes as much as .8 volts difference for very short periods, the Delta SOC, difference in voltage between packs, always shows 0%, which is good. The whole pack seems to be improving every drive with it getting consistent system balancing. It has been staying between 55 to 65 % SOC most of the time, going no lower than 50% or higher than 75%.
     
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  17. Mendel Leisk

    Mendel Leisk Lapsed Cargo Cultist

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    Can you elaborate? Any pictures?
     
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  18. SFO

    SFO Senior Member

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  19. grid

    grid Active Member

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    Dr hybrid
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    Driving to LA and back this weekend up the hills so I need this app to monitor regen.

     
    #19 grid, Apr 19, 2018 at 10:47 PM
    Last edited: Apr 19, 2018 at 11:28 PM
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  20. Old Wrench It

    Old Wrench It New Member

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    Yes, Dr Hybrid.
    My son got off work early today, he purchased a 2012 Prius a few weeks ago. We took out the fam for the battery pack. While he was cleaning that I installed an extra vent tube.
     

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