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Thread: temperature management for long term battery performance?

              
   
   
  1. #11
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    Quote Originally Posted by ldopa_chicago View Post
    I'm pondering total temperature regulation. Now, to determine if the costs justify the benefits, we need to know what the temperatures throughout the pack actually look like.
    As have I been for a long while now - and I absolutely agree, it's well worth studying.

    Quote Originally Posted by ldopa_chicago View Post
    In my semi-relevant experience with small lithium chargers, charging at a 0.5C with large airgaps between cells results roughly in an average 10 deg C rise above ambient*. There is a gradient across the pack, with the cells at either end being several degrees cooler. For a pack with fixed module/cell position this will result in some degree of imbalanced cell degradation over time. Now like you said, most of us are charging at pretty low rates.
    This is an excellent reference case, and I'd be curious to know if that data comes from cylindrical or pouch type cells, I assume LTO which would imply pouches?

    Quote Originally Posted by ldopa_chicago View Post
    Now, I don't know that this really matters. Maybe it is more academic. Maybe the better way to handle it is to just try to keep the pack at a consistent temp with insulation/heatsinking or maybe it's just not worth addressing.
    Again, I'm in agreement - I think the first priority is to keep the temperature gradient as even as possible throughout the pack, and work on regulation then from there.

    Quote Originally Posted by Stevo View Post
    I was wondering about the temperature distribution throughout the pack. I was thinking I would monitor the temp of my pack somewhere centrally. Not sure if the temps are consistent throughout, or more pronounced near the electrodes.
    Given the cost of a few thermocouples, I'd be inclined to monitor centrally at each 20% of the length of the pack at least.

    Quote Originally Posted by Stevo View Post
    I wonder if something like a reptile heating pad might work well, ...
    I know Li cells degrade faster in very cold temps. My bike would have a very noticeable decrease in power and range when riding in temps below 5*C.
    I think one should be more concerned about cooling Tesla type batteries than Nissan Leaf cells.
    The heater pad setup could be of benefit I believe. I reckon the trick would be to use it the same way that the Norther Finns, Norwegians and Swedes use sump heaters in public car parks in winter.
    In short, as long as the car is parked, it's plugged in and the heater blanket prevents the pack from getting too cold, once it's in use it'll maintain temperature itself as long as there's not too much airflow over it.
    The harder part it shedding heat when the pack has been worked hard though.

    Quote Originally Posted by T Rush View Post
    my Wife drives a Nissan Leaf, which has no battery warming or cooling.....

    but in the winter, yes we do notice problems with charging and range when its very cold
    I've a 2012 Leaf with 253000km on it now. You do notice the range drop by about 15% in winter even here (and we have it pretty mild), and the fast chargers will start to slow down as the BMS limits charge rates to respect the thermal related constraints. Standard charger doesn't really amount to much more than a trickle for that pack in any circumstance though so we've never had any issues with it.

  2. #12
    Senior Member Stevo's Avatar
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    Quote Originally Posted by Spoonman View Post

    Given the cost of a few thermocouples, I'd be inclined to monitor centrally at each 20% of the length of the pack at least.
    They aren't thermocouplers, they are actually a transistor sensor...
    That's an interesting idea. I was contemplating having one sensor mid-pack centrally near the center of the body of the pouches, then putting one each at the - and + ends of the pack closer to the electrodes.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
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  3. #13
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    Quote Originally Posted by Stevo View Post
    They aren't thermocouplers, they are actually a transistor sensor...
    You referring to the stock units that come in the leaf packs?

    Haven't actually considered using them as I haven't even looked into their characteristics - I was just thinking more along the lines of t-type thermocouples.
    Cheap as chips and more than accurate enough.

  4. #14
    Senior Member Stevo's Avatar
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    No, the DS18B20 are for Raspberry Pi and Arduino microcontrollers. You can get em cheap on eBay in a waterproofed version or cheaper yet in an unwired pcb version

    Sent from my Pixel 2 using Tapatalk
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
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