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Battery temperature going above 50°C/122°F while discharging

Discussion in 'General Discussion' started by curiosity, Apr 11, 2016.

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  1. I use the "slow discharge" method as mentioned in the manual

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  2. I use the "fast discharge" method as mentioned in the manual

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  3. I use an external discharger unit

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  4. I just let the auto-discharge feature kick in to discharge it below 65% and that's it

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  1. curiosity

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    Hello,

    I am using the slow discharge method provided in the manual (page 21) for my Intelligent Flight Battery that I use for my Phantom 3 Advanced as mentioned below.

    How to discharge your Intelligent Flight Battery:
    Slow: Place the Intelligent Flight Battery into the Phantom 3 Advanced’s Battery Compartment and turn it on. Leave it on until there is less than 8% of power left, or until the battery can no longer be turned on. Launch the DJI GO app to check battery levels.​

    While doing this, I notice that my battery temperature is going up to and above 50°C (122°F), which is way above the operating temperature of this battery that is stated in its specifications.

    However, there has been no warning in the DJI Go app or a mechanism to prevent this method from heating up the battery this much so far. I wonder if this is safe at all or whether if this method is a bad practice and should not be the primary way to discharge. I am afraid that this much heat is going to degrade my battery life in the long run.

    I understand that there is also an option to fast discharge by running the P3A and hovering but I can't always find a place and time to do this, so I choose the slow discharge method which is much more convenient for me to do so. I just let it sit inside my room as described in the method and that's it. I'm wondering if this is okay or not.

    I've contacted DJI support to get their opinion as well and will update this thread when I receive it.

    Thank you.
     
    #1 curiosity, Apr 11, 2016
    Last edited: Apr 12, 2016
  2. Ramphex

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    I would imagine it heat soaks due to no cross breeze because of the aircraft being stationary. I don't think those are critical temperatures but maybe consider to just let it hover or fly it around for better temperatures and faster discharge.
     
  3. curiosity

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    You're right, the reason it's getting that hot is that there is no wind created by the propellers.

    They are probably not critical but they don't seem to be desired temperatures at all either (just found a screenshot recording 54°C/129°F). So I am aware that it probably won't cause any harm in an instance but I'm thinking more about its long term effects. Something tells me that this practice doesn't seem to be the best one.
     
    #3 curiosity, Apr 11, 2016
    Last edited: Apr 12, 2016
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  4. Mark The Droner

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    I always thought the safe temp range was 0-40C, but was referring to air temp, not battery temp.

    Some self-proclaimed battery expert posted here once that a battery temp of 60C is the magic temp where the Lipo becomes possibly volatile.
     
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  5. curiosity

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    Thanks for the information Marknmd, I agree with you on the safe temperature range that it is the environment temperature, not the battery itself.

    So what I need to know is that what is the safe temperature range for the battery itself. As it becomes much hotter than the environment around it. 60C seems too much for me, but I don't have any factual information that I can use to prove it. The manual doesn't mention anything about this as well.

    DJI support asked me to get a screenshot of the battery temperature reaching above 50C and the voltage levels at that temperature. I am not sure if seeing acceptable voltage levels at a specific temperature is enough to say that it would be safe to operate at that temperature. It rather seems like to me that they don't have this information as well and are just trying to 'see' by chance if something goes wrong, like, in battery voltage levels, etc.
     
  6. TWP723

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    140 degrees seems a little high for the battery to me. Maybe not but..
     
  7. Mark The Droner

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    60C seems too much to me too. I would stay away from 60 C. If it got to 50C during the discharge, I would take it out of the craft and let it cool down. Then continue later if needed.

    BTW, the same guy that posted about 60C said the ideal operating battery temp is 30C - 35C. Another guy made a video showing that anything below a battery temp of 20C is "cold" and ideally would be warmed up before flying in cold weather. Point is, what may seem comfortable or too warm or too hot to you is not necessarily comfortable or too warm or too hot to your lipo battery.
     
  8. Ramphex

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  9. Mark The Droner

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    We don't fly with Lithium Ion batteries. We use Lipos which are next-generation. There are similarities but differences too.
     
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  10. Imabiggles

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    BS - Lipos are a form of Lithium Ion batteries. Certain hard cell batteries have the exact same chemistry as do the soft cells. Certain soft cells differ between each other due to the electrolyte make up. Rules for the soft cells (what we call lipos) are generally more restrictive than the hard cell flavor. If your point is not all batteries are the same, point taken - but all our batteries are forms of lithium ion cells, just like all lead acid batteries are variations of lead acid cells and the chart above is a good guideline.
     
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  11. Ramphex

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    Actual name is Lithium-ion Polymer
     
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  12. curiosity

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    Okay, I've searched through Google to find an answer to this, and below are some references from different sites where I quoted necessary part.

    http://www.st.ewi.tudelft.nl/~koen/in4073/Resources/LiPoUsage.pdf
    • Lithium polymer batteries should not be operated in temperatures exceeding 140 degrees Fahrenheit.
    Lipo Temperature - does anyone check their battery temp?
    • I've had one 2S 5000 puff on me. The battery was 126F at the time.
    • My 3S LiPos would also run between 120 and 125F, but in my opinion that's too hot. I've heard the max temp for LiPos is 140F, but that's just crazy. If you want your packs to last you should keep them below 110F tops and under 100F is ideally where you want to be.
    • 140f/60c is the general temperature ceiling for lipos
    • I have read 140º is the limit as well.
    Lipo (Lithium) Battery Safety Guide
    • LiPo batteries should be charged within a temperature range of 0C to 50C. Batteries charged outside this temperature range may experience leakage, heat generation or cell damage.
    • Do not store your LiPo pack in extreme temperatures below 0C or above 50C.
    Handling of LiPo batteries
    • When operating, never allow battery temp to exceed 143F.
    • If your packs are hitting more than 120*F then they are being overdrawn. "The general rule is if you can't comfortably hold a LiPo pack tightly in your hand after using it, it's way too hot."
    • Lipo's ~ 140*F (60*C) max, ideally 100/120*F (38/49*C).........
    • 143F is the absolute maximum Lipo temp above which there is very high risk of fire or explosion.
    • I actually keep operating temperatures in 80-110F (110F is the maximum safe charge temperature).
    • Once you hit that critical temperature above 143 or it puffs you can't do anything to stop the reaction from proceeding
    More performance from your LiPo (Tutorial)
    • 140°F (60°C) is the maximum safe temperature
    Safe operating temperature for Lipos - RC Groups
    • Operating Temperature: Charge: 32 to 113 degrees F Discharge: 32 to 140 degrees F
    • A lot of testing / reasearch by another major LiPoly in RC applications vendow indicated that charging when battery is below 50F sharged should be limited to 4.1V per cell and that temperatures above 125F have a rather major impact on life cycles.
    • I personally try to keep my packs under 120F post discharge. If they get hotter than this, I either back off on the left stick or move the packs to a less demanding application.
    Operating Temperature of LiPo Batteries - RC Groups
    • Between 85F and 125 F is where they perform well and warmer is better but above 125F they start to die fater ( fewer cycles).
    • I personally do not like my lipolys to ever go over 125°F.
    LiPo discharge performance over temp - RC Groups
    • Best performance with most LiPolys is in the 125F to 140F range however 140F is also the upper limit for good cell life.
    So in general, 60C/140F seems like the point where you should stop using the battery and let it cool down. But this doesn't necessarily mean that it's safe to get close to 60C/140F regularly, which is what is happening in my case, even though I'm following the procedure documented in the manual. I am quite sure that I can hit 60C/140F if I wait long enough.

    Just to see how fast it heats up, I started with a fully charged (100%) battery and below are my observations;

    2:22 PM
    100%
    4.29V/17.2V
    27C/81F​

    2:31 PM (+9 min)
    95%
    4.25V/17.0V
    30C/86F (+3C/+5F)​

    2:44 PM (+13 min)
    90%
    4.20V/16.8V
    35C/95F (+5C/+9F)​

    3:01 PM (+17 min)
    83%
    4.12V/16.5V
    42C/107F (+7C/+12F)​

    3:08 PM (+7 min)
    80%
    4.09V/16.4V
    44C/111F (+2C/+4F)​

    3:17 PM (+9 min)
    76%
    4.06V/16.3V
    46C/115F (+2C/+4F)​

    3:22 PM (+4 min)
    73%
    4.04V/16.2V
    47C/117F (+1C/+2F)​

    3:33 PM (+11 min)
    69%
    3.99V/16.0V
    49C/120F (+2C/+3F)​

    3:42 PM (+9 min)
    65%
    3.96V/15.9V
    51C/124F (+2C/+4F)​

    4:00 PM (+18 min)
    56%
    3.89V/15.6V
    53C/127F (+2C/+3F)​

    4:21 PM (+21 min)
    46%
    3.82V/15.3V
    55C/131F (+2C/+4F)​

    At 4:21 PM mark, my cell voltages were 3.82V, 3.83V, 3.83V, 3.83V - so all were good. And yes, I know that I'm still below the ultimate 60C/140F mark but still, this is a lot of heat, very close to the limit and the battery is being exposed to this heat for a very long time (above 45C/113F for more than an hour). I think this will eventually degrade the battery life quicker than the "fast discharge" method, where we're supposed to hover with the propellers on.

    I don't really feel safe doing this, it really doesn't look like the best practice but more like a secondary way to discharge if you can't perform the "fast discharge". I'm just trying to get the best bang for the buck; the batteries are not cheap and are essential to a safe flight. I don't want to lose my batteries nor my P3A mid-air :). But still, sorry if I look like I'm over-reacting!

    P.S. I have two batteries where the most used one only experienced 9 cycles and this behaviour can be seen on both.

    P.S I have waited a little bit more until the battery charge dropped to 30%, where the temperature on the DJI Go app was showing 56C/133F. At this point, I powered of the unit and removed the battery, then quickly used a temperature gun to measure the surface temperature of the battery, which showed 51C/124F at the hottest point and around 48C/118F on average. This whole process took less 15 seconds, so there was not much time for it to cool down.

    P.S. Also, the overall hottest point on the P3A was near the ventilation openings of the Vision Positioning Sensor (VPS), which I read about 65C/149F max - the area around the ultrasonic sensors were literally too hot to touch.

    P.S. Apparently, on the battery itself, there is a warning on the side that goes like this; "Stop using or charging the battery immediately whenever it swells up, leaks and its temperature over 160°F (71°C) or anything else abnormal occurs.".
     
    #12 curiosity, Apr 12, 2016
    Last edited: Apr 12, 2016
  13. Ramphex

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    Just curious again, why not just fly/hover until they discharge or let them self discharge after a set period of time with regular ventilation vs inside an inclosed quad.
     
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  14. curiosity

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    Thanks for your interest Ramphex, again, sorry if I'm over-reacting.

    The reason I am trying to understand this is because sometimes, I charge both my batteries to 100%, thinking that I would go out to fly in an hour or so, but then things don't go as planned and I have to postpone my hobby to the next weekend. In times like this, I can't let it hover since I'm not going outside with my P3A. And I don't feel safe running it in my house, which is quite tight in terms of free space.

    The reason I'm not using the auto-discharge feature is that even though it's really practical to let them discharge themselves automatically, they only get discharged to just below 65%, which is above the suggested storage charge percentage (which is mentioned as 30 to 50% in the manual).