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Thread: temperature management for long term battery performance?

              
   
   
  1. #1
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    temperature management for long term battery performance?

    i feel like battery temperature management is usually an after thought. so long as the pack is big enough, then it is assumed that the individual cells won't have enough amps running through them to make much of a difference. and this may be true for the short term, but what about long term? we want these batteries to last us 5+ years right? and temperature management is a critical component of battery longevity. So i'm wondering what people's thoughts are on maintaining the batteries through continuous usage, and how it has worked out for them

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    Not much of a concern where leaf modules are involved - if you're using 18650's then depending on the discharge 'C' rate, some consideration would be advisable alright.
    It's a point I've been dwelling on quite a lot over the years bit without instrumented data it's impossible to gauge the extent of the requirement.

    I think the first step would be establish a record of the temperature gradient along the pack under standard use case scenarios and then work from there with the ideal goal being the maintenance of a uniform temperature throughout the pack, and maintained within the 5-30degreeC range.

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    Senior Member Stevo's Avatar
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    I'll be using "Virtuino" app on my android cell phone to monitor coolant temps as well as battery temps.
    The app is cool because it will store and display min and max temps acquired. The temp sensors are very affordable. They wire daisy chain and you can have as many temp sensors as you need.
    DS18B20 https://www.sparkfun.com/products/245
    Last edited by Stevo; 4 Days Ago at 0820.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: http://elmoto.net/showthread.php?t=4354

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    Quote Originally Posted by Spoonman View Post
    Not much of a concern where leaf modules are involved
    I can't agree with this part but otherwise agree with your post. As part of my job I design charger systems for lithium batteries, albeit much small ones. Temperature is one of the most important factors in terms of safety and longevity. The easiest thing to control is charge temperature. According to the JEITA (Japanese Electronics and Information Technology Association), it is recommended than NO charging occur below 0 deg C. Between 0 and 10 deg C, one should charge at a maximum of 0.5C. Between 10 and 45 deg C, charge up to 1C. Between 45 and 50 deg C, you can charge at 1C but only to a reduced voltage of 4.15V per cell (for 4.2V cells). Finally, between 50 and 60 deg C, you can charge again at 1C but only up to 4.10V max per cell.

    Personally, I would take a more conservative approach because the ramifications are much greater with an EV pack versus a single cell consumer-grade pack. I would not charge below 10C or above 45C.

    I've entertained some sort of liquid temperature control platform using flat ribbon "hose" to deliver coolant throughout the pack and a radiator (with electric fan) for cooling as well as a heating element for warming a cold pack (this would run off of a 12V lead acid aux battery). Maybe one day...but I gotta get my bike done before I plan anymore upgrades! Scope creep is a constant threat.

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    Quote Originally Posted by Stevo View Post
    I'll be using "Virtuino" app on my android cell phone to monitor coolant temps as well as battery temps.
    The app is cool because it will store and display min and max temps acquired. The temp sensors are very affordable. They wire daisy chain and you can have as many temp sensors as you need.
    DS18B20 https://www.sparkfun.com/products/245
    Also, that is really cool and a great idea. Thanks for sharing.

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    oh boy.. cooling and heating elements? If I go ahead with this build i have in mind, I do plan to not go to 100% charge, and only go up to 4.1V, despite the temperature. 20-80% SOC is the sweet spot. but I suppose charging temperature is the most critical consideration. discharging temperature is less of a problem, right? the operating voltage is low enough to minimize electrolyte breakdown during fast discharge. it's during charging, when the over potential is high, that you start losing lithium to side reactions. am i understanding this correctly (battery experts)?

    different question: in the case when the SOC is kept between 20-80%, would it be a good idea (or necessary) to bottom balance the batteries once every 5-10 cycles or so?

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    Quote Originally Posted by ldopa_chicago View Post
    I can't agree with this part but otherwise agree with your post....

    ...I design charger systems for lithium batteries, albeit much small ones...

    I understand your concern and academically you're correct, however herein lies the reason for my assertion.

    The hot and cold temperature effects you're alluding to are *heavily* coupled with the charge or discharge rate as defined in relative terms (ie: 'C').
    With smaller packs, this can easily mean that charging above 1C, or even 0.5C, can be detrimental.

    Now academically you're absolutely correct that this should be a concern; practically however, even achieving 0.5C in a leaf module pack arranged in a single string, means charging at 30A.
    How likely this is will of course be voltage dependent, but if we assume the worst case 48V system scenario, then you're still talking about 1.5kW which is literally right on the edge of being the largest charger that anyone, in the context of this community, is going to put into a motorcycle with a pack of that nature.

    All that being said - I agree with you. Charging should not be attempted at pack temperatures below 0degrees or above 40degrees.
    In the context of these larger modules which have substantial thermal mass however, this still does not necessarily mean there's a need to monitor the pack temperature itself - ambient reference will, under all but the most extreme circumstances, provide a more than adequate reference in this regard.

    In closing - I'm not for one minute suggesting that having this data and this sort of integration is a bad thing, or isn't worthwhile - all I'm saying is that in the case of the Leaf modules specifically, I wouldn't be particularly concerned.
    Last edited by Spoonman; 3 Days Ago at 0207.

  8. #8
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    You make some very valid points, Spoonman.

    Like you say, a leaf pack will high a high thermal mass. We can safely assume that there will be a temperature gradient across the pack. Ideally, I'm not just advocating temperature monitoring, 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.

    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. My charger only does 1/3C, for instance.

    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. I do like discussing it though!

    *this is the peak rise, which tends to occur sometime around the CC/CV transition, since that's the peak power.

  9. #9
    Senior Member Stevo's Avatar
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    Quote Originally Posted by ldopa_chicago View Post
    You make some very valid points, Spoonman.

    Like you say, a leaf pack will high a high thermal mass. We can safely assume that there will be a temperature gradient across the pack. Ideally, I'm not just advocating temperature monitoring, 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.

    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. My charger only does 1/3C, for instance.
    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.
    I agree with Spoonman... the Leaf modules are robust and dont need cooling. BUT, if riding in cold temps, a heating element would be a very good mod. I wonder if something like a reptile heating pad might work well, like one of these: http://https://www.chewy.com/zilla-heat-mats-reptile-terrarium/dp/129072?utm_source=google-product&utm_medium=cpc&utm_campaign=f&utm_content=Zilla&utm_term=&gclid=Cj0KCQjwx43ZBRCeARIsANzpzb_IlkyaODtmdiTNDHFD SeGqqDUivpnU8CrQI06FKQQeMufeLdxBLZIaAqiOEALw_wcB
    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.
    Last edited by Stevo; 3 Days Ago at 0924.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: http://elmoto.net/showthread.php?t=4354

  10. #10
    Senior Member T Rush's Avatar
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    my Wife drives a Nissan Leaf, which has no battery warming or cooling.....in the summer time(pretty darn hot here now) we don't really notice any ill effects, tho I think I read where some Nissan Leaf owners had issues in other even hotter climates

    but in the winter, yes we do notice problems with charging and range when its very cold

    I'm sure these extremes(our temp can vary as much as 120F between summer and winter here) do effect long term performance
    ...so if she does keep this Leaf(she wants the new one....but I trying to talk her into the Chevy Bolt, which has battery heating and cooling when charging) I will want to install a heated garage foor


    I did see some videos of a guy dyno tuning an electric motorcycle and using a heater to warm the batteries....but otherwise all motorcycles aren't really the nicest to use in temperature extremes, so it would be less of a problem if people mostly ride and recharge them in milder weather

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