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Electric Vehicle (EV) battery cooling systems

Discussion in 'Off Topic [BG]' started by Rodent, Mar 6, 2018.


  1. Rodent

    Rodent A Killer Pickup Line™ Commercial User

    Dec 20, 2004
    Upper Left Corner (Seattle)
    Player-Builder-Founder: Honey Badger Pickups & Regenerate Guitar Works
    For those in the know on aspects of EV battery cooling systems (anywhere in this specialty system from system architecture to system design to fabrication/assembly to field maintenance), what can you share that gets your coffee percolating and/or your souffle collapsing when it comes to your expertise on this?

    audi-a3sportbacke-tron-8va-2014_26.jpg 701-Audi-Q8-concept-750x530.jpg

    I'm about to engage on a project focused on this topic - a topic that is relatively new to me. My vantage point and consulting expertise is that from an engineering software tools for design/manufacturing perspective with extensive experience on similar type systems in other industries. I welcome Google as a valued friend here, but also recognize that there's only so much info shared by the many companies striving to be leaders on this specific topic.

    Got a journal article or trade workflow reference you can post a link to? Have a story to share? Are you a patent holder looking to let the world know about your research and/or technology discoveries?

    Feel welcome to post away and keep this thread rolling!
     
  2. MJ5150

    MJ5150 Moderator Staff Member Supporting Member

    Apr 12, 2001
    Olympia, WA
    This thread has @malthumb written all over it.
    I have nothing to contribute, but I am going to pay attention and learn something.

    -Mike
     
    GregC likes this.
  3. T_Bone_TL

    T_Bone_TL

    Jan 10, 2013
    NW Mass/SW VT
    Seems like a fairly straightforward heat exchanger setup to my enginerd brain. Not that they seem to have the option of routing the heated coolant through the cupholders (or not, depending on desired beverage temperature) but that would add complexity. Close as I can come to perking coffee from it, though. Dang well should put it through a heater core to reduce electric heating load if there's any overlap of "need to cool the battery" and cold weather, since otherwise cabin heat is wasting power in an EV.

    Obvious-seeming issues are size of cell packs limiting surface area to contact heat exchanger (smaller sub-packs get you more cooling exposure at the cost of more packs and less overall energy density, since any space taken up by the heat exchangers is not space taken up by batteries.) At the cost of mess and complexity using a non-conductive heat transfer fluid in direct contact with the cells (distribute the cold stuff into the bottom, collect the hot stuff on top and ship it to the radiator) would probably offer the best cooling contact and energy density, but the mess and potential leaks are not minor issues. There might or might not be places where adding heat pipes to the mix (is there dead space in the cell-packs between cells? That would be an obvious place) could help moving heat where it needs to go in a space-efficient manner.

    Many years as an all purpose lab rat and enginerd, none in EV design.
     
    Last edited: Mar 6, 2018
  4. MattZilla

    MattZilla

    Jun 26, 2013
    CNY
    There's a handful of mildly useful content on thekneeslider.com, but I don't think it's indexed very well and may take a few hours-days to sift through.

    Did I read right, that you engineer the software tools?

    Right now I'm working as a patternmaker at a prototype/small batch firm and I have to use surfcam which takes about four times as long to modify program files to add draft, machine stock, and create cores and coreboxes as any of the programs we used in school, maybe partially due to our somewhat older, bluescreen-prone computers. The bottom housing, if the cooling pipe is not actually moulded into it, seems pretty easy depending on the wall thickness and how tight the tolerances are.

    Bunch of short loosely linked stories for procrastination:

    My family's business is two-way radio and I grew up tearing apart and rebuilding radio and power supply chassis from the 70s through the 90s, most of which used the outer casing as a heat sink to some degree, even the mobile/handhelds. Really, only the cheap junk that the volunteer fire fighters bought on their own dime didn't have the same mini-finned heat-sink chassis designing as the GE/Ericsson and Motorola stuff I usually saw.

    On some weekends I help my cousin with his ironworking company, installing the gates, headlocks, etc. in dairy barns, very often using all of the hell out of these big, bad XR series DeWalt impact drills. They get HOT. I'm surprised that there's no cooling fins as found on the old radio chassis on them. He usually gets about eight months out of one before having to send it to DeWalt for a rebuild.

    When the teslas first came out I, a regular stick shift rwd driving hillbilly, thought I'd never consider driving an RC car that'd need to charge for five times the available driving time, but, just as a chainsaw-powered skateboard seems kind of fun, so too does a gigantic-DeWalt powered car: vVVVVVVoopchk! vVVVVVVVVVVVVoopchk!

    My cousin's crew stops work below 10F in barns when the drapes haven't been installed yet, because that's where it becomes a waste as the cold air out in the barn just kills the batteries too quickly for a whole crew to be productive even with us having three or more spare batteries in our pockets and the rest racked or charging in our heated break trailer. Too much stopping to swap batteries and/or run to the trailer- rythym killer and time waster. Though they heat up a bit when cranking one high-friction nut after another, they still discharge quite quickly as compared to any regular spring/summer/fall day.

    Cars have to be able to travel >200 miles at -30F after sitting out in a -30F parking lot for hours or even days to be deemed not useless as an only car for anyone living north of Maryland. That means that you need more than just battery cooling, like modern guitars have two-way truss rods, an EV needs total temperature management (cooling and heating) on the battery packs, yeah? I don't have a method in mind of how you accomplish that, but it seems like a necessary bulletpoint to have up on your whiteboard. I doubt I'd put my name on a water-cooled anything that didn't also have some amount of air-cooling capability on its outer casing. A tricky balancing act for a product that is unlikely to find value in the used market- is anyone going to buy off-lease EVs? Do the mfr's field that concern from the dealerships? No one is buying a BMW i8 off lease, that's for sure.

    Most EV customers have to have heated garages at home and at work if they wish to use them in cold winters. Other side of the same coin: An EV owner between Mexico and Ohio is going to want (need?) more than just antifreeze piped to and from a radiator with just-above-tarmac air flowing through it to cool that battery and the motor... it's gonna need to have a lil AC cold-air blower chilling the system, no?
     
    Last edited: Mar 6, 2018
  5. OldDog52

    OldDog52 Gold Supporting Member

    Jan 1, 2011
  6. BurnOut

    BurnOut It's The Billy Baloney Show Supporting Member

    Feb 1, 2015
    The Natti
    It was a problem on the solar electric plane they flew around the world. The batteries didn't have cooling, overheated and had to be replaced. Had to modify their storage with an air vent to prevent it from happening again.
     
  7. Shouldn't all that heat be driving the power steering with a steam powered ram set?
     
  8. I read about that also. I have two fully electric cars. Unlike an ICE car, the battery is the main major component of the vehicle and must be kept cool during charging and driving. My 2008 little roaster has a fairly complex cooling system utilizing anti freeze with a radiator to keep the battery cool. If the very expensive battery gets too hot, then it's life is shortened and must be replaced. I am not sure if using an air cooled system for cool off is a good engineering choice for automobiles. When charging, the vehicle is not moving and it might be difficult to get sufficient airflow around the battery.

    Fans and radiator.
    IMG_0772.JPG
    Anti Freeze filler and monitor.
    IMG_0771.JPG
     
    Last edited: Mar 7, 2018
    OldDog52 and BurnOut like this.
  9. OldDog52

    OldDog52 Gold Supporting Member

    Jan 1, 2011
    From what I’ve read thermal battery management is most critical during DC fast charging. More or less a non issue for Level 1 & 2 charging. Interestingly VW advises against doing multiple successive DC fast charges. They strongly recommended if you’re doing fast charging that you alternate between DC fast charging and Level 2 (or 1). Don’t know what other EVs say about that.
     
  10. I have four options choices for charging. The main default choice is "Standard Charge" which charges the battery to 80 percent giving approximately a 180 mile range if you drive sanely. (I don't as it is fun to smoke most Ferrari's, Vette's and Porsche's:D) It also has a "Range Mode Charge" option which charges the battery at 100% and gives you an approximate 220 mile range. But when charging at 100 percent the batteries get extra hot. The car's owner's manual states to use the "Range Charge" sparingly and only if a long trip is anticipated. It also states that it will shorten battery life. With that said, I have never used it and the 10 year old battery still has 96 percent of it's original power output.
     
    Last edited: Mar 7, 2018
  11. T_Bone_TL

    T_Bone_TL

    Jan 10, 2013
    NW Mass/SW VT
    In the "charging" (other than regenerative braking) case, you (should) have plenty of power available to run fans (if air cooling) or even active cooling (air-conditioning/heat pump.) My Corvair was air-cooled, and it had a big fan pumping lots of air at any speed it was purported to be unsafe at. There are always tradeoffs, and there are different techniques to make each major choice (direct air cooling .vs. liquid-pumped-to-radiator air cooling) work better on a system-wide level. There are also overall system choices, such as "is it OK to limit performance if the driver wants to take the car out on the salt flats at 40 °C and we have to keep the battery below 45 °C and there's only so much heat we can dump with a 5 °C differential" or not. You need a really big radiator to make that case not be a limit; Or creative responses like adding a water tank which you spray/mist/fog on certain subsystems to get an evaporative cooling boost (to the radiator exterior, or air-cooling fins) when needed, and have to refill before the next use, and drain before winter (or add vodka to before winter...or have a valve that dumps it automatically at 1 °C.)

    In my personal experience of VWs, (closest thing to an Audi I've got experience with) the modern ones tended to have overly complex electro-mechanical solutions (to problems that other makes dealt with by simple, reliable, mechanical only solutions) that were great for planned obsolescence, and bad for me ever buying a VW again. The gas cap door that every other car that locks it uses a long cable for? A switch, a motor, and a short cable. Which failed, repeatedly, and we learned to pry the gas flap open. While I have seen other cars use electric mirrors, the VW control for them failed, and I prefer mechanical given a choice. Not a car you wanted to own much past 8 years of age.
     
    Stewie26 likes this.
  12. Rodent

    Rodent A Killer Pickup Line™ Commercial User

    Dec 20, 2004
    Upper Left Corner (Seattle)
    Player-Builder-Founder: Honey Badger Pickups & Regenerate Guitar Works
  13. Rodent

    Rodent A Killer Pickup Line™ Commercial User

    Dec 20, 2004
    Upper Left Corner (Seattle)
    Player-Builder-Founder: Honey Badger Pickups & Regenerate Guitar Works
    great discussion so far!
     

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