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Intelligent Battery Issues

Discussion in 'Pro/Adv Discussion' started by ghinson, Dec 8, 2015.

  1. ghinson

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    I am reading a lot online about issues with faulty readouts from the battery LEDs and the app for batteries that are flown after sitting for a period of time since last charge. What is apparent is if you fly without fully charging the battery on the day of the flight, you are at risk of a sudden, potentially catastrophic battery failure.

    (Trust me, I know, I doing the "You got to do better than 30%" dance with DJI support right now.)

    What is not clear is exactly what the cause is and how to replicate the problem. I am wondering what the best way to use the Auto Discharge function is. I think it defaults to 10 days. Would it be smart to set it to 1-2 days so that you are forced to recharge on the day of flight? Others (in the DJI forum) seem to be saying that the Auto Discharge function might be the problem. Once a battery goes in to Auto Discharge, it can no longer be trusted.

    Any thoughts?

    Either way, given the number of drop-out-of-the-sky reports I am reading, I hope DJI comes out with some sort of notice about the problem and updates their manuals.
     
  2. Wacker2611

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    I agree, I think once you get used to the idea that you should never fly with a depleted battery that's been left for more than a day, and always charge fully (until the lights go out), you'll be fine. But I wouldn't have known that if it wasn't for this great forum.
     
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  3. msinger

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    It would be smart to set it to 2 days so your battery does not sit fully charged for a long period of time. 1 day is kind of short and your battery could start discharging itself if you decide to charge it the day before you fly.

    I don't really understand the concept of forcing someone to charge their battery before flying. It's an absolute requirement.
     
  4. ghinson

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    Here's an example of why DJI needs to make this more obvious. From their tutorials:

    12305984_10207011466617619_1308200270_n.jpg
     
  5. msinger

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    You could technically fly at 55%+. One of the problems is that some people like to fly their Phantoms like stunt machines and they don't realize the battery cells could spike to extremely low levels when the battery is that low and under stress. Ultimately, it could cause the Phantom to land immediately or the battery to shut off mid-air. But, if everyone knew how to monitor their battery voltage, none of this would really be a big deal.
     
  6. alokbhargava

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    You may note the following points to get best out of your batteries:

    1. Batteries degrade as you charge and discharge them. That means setting an auto discharge for 1-2 days will not be advisable unless you know you are going out tomorrow for long. Setting at 7-10 days seems to be a reasonable value. If you fly only during weekends, set the value to 7 days.

    2. Storing batteries with full discharge is not advisable. That means you should set a period after batteries go into discharge mode to 50-60%.

    3. Batteries discharge curve changes over period of time. We need deep discharge cycle at least after 20-25 discharges. Deep cycle procedure is (assuming current charge level is 60%):

    60% >>>>100% >>>>8% >>>>100%

    This would definitely give new life to your batteries and would bring back its known discharge predictable characteristics.

    4. If batteries are kept for few days unused, top them to 100% before using them.

    5. Never allow batteries to discharge fully, you will lose them. If you are going out for very long say 1 year, make someone to take care of them in your absence.

    6. Charging and discharging beyond their C rating, will damage them. Batteries may catch fire in such cases. Be sure of the Chargers being used. Never use these batteries for other purposes. Be careful if you are seeing ESC failures as failed ESC may not be able to limit the current to the batteries.

    Batteries are the life to your P3, better take care of them.
     
    #6 alokbhargava, Dec 8, 2015
    Last edited: Dec 8, 2015
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  7. N017RW

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    This so called 'deep discharge' has nothing to do with LiPo chemistry and is not found in any manufacturers' literature.
    It is purely to address the worst feature of the battery and that is the intelligent interface.
     
  8. syotr

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    I still don't understand the logic behind shutting off the motors in air if the battery is low or temporarily dips to a low level. I would much rather save the Phantom from crashing than worry about ruining the battery.
     
  9. N017RW

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    It's not a matter of logic or a programmed response.
    Most of today's devices are regulated past the battery and contain embedded processors.

    If the voltage drops too low and for too long it will interrupt regulation output. At this point the embedded microprocessors will be forced to reset and control function will temporarily cease.
     
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  10. alokbhargava

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    I don't thin their is a logic to shut off motors at any point. I agree with you, it's better to kill batteries rather ruining your P3. I feel if the batteries are drained off, they can't give enough current to keep P3 flying and if load on the motor is more than what it can take care off, motors tend to stall.

    Also we need minimum voltage to sustain electronic system. We have just one battery in P3 to feed power to motors and to maintain electronics.

    Battery voltage is flat up to certain low charge levels and then it rapidly droops down making everything unstable. Land your P3 sooner when you get low voltage warning. We always assume that warning level is correct. This could go wrong if the batteries were not calibrated.

    I have seen many other varieties of LiPo batteries in the market they are intelligent to shutoff supply in case of critical charge level is reached. We don't need such batteries for flying. Hope P3 batteries do not have shut off mechanism.
     
    #10 alokbhargava, Dec 8, 2015
    Last edited: Dec 8, 2015
  11. syotr

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    It is still a design issue, whether it is in the battery logic or flight controller. My P1 and my other multirotors that use a NAZA controller do not have this issue. If the voltage gets low, I get a warning light in plenty of time to land. If I push it too far, I may damage the battery but the motors do not just shut down. If I am flying over water, I can still steer it back over land. I might crash but hopefully from a lower altitude and not in the river.
    Yes, we need a minimum voltage to sustain the electronics, probably 5 volts. That is not the issue. The voltage is nowhere near that low.
     
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  12. Donw35

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    what is the process when you know you will not be flying for weeks to months (weather) ?

    I flew my P3P on Sunday, This is my first "expensive" Quad so I come in and land once I hit 30% and when I hit 40% I make sure I am over land and altitude is not above 40 feet, seem 40% to 30% happens quickly.

    I haven't charged them yet, I was going to in a few days with the expectation of flying Friday, is this a good idea ?

    Thanks
     
  13. 4wd

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    If you run them down well below 50% and won't need full charge for several days, it's best to charge them until the third LED is flashing.
    If you go a bit over 50% that's about ideal.
    In store you want two LEDs on if tested by briefly pressing the button.
    Leaving them discharged is probably as undesirable as regularly leaving them full for more than a week.
     
  14. jingthing

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    I normally try to be on the ground as they hit 30% but often it winds up at 27-28%. if i,m not going to have time to fly for some days(like at the moment) i do as 4wd said, take them up on charge till the 3rd led begins to flash then take them off,
    I admit i dont feel comfortable with the idea of letting them self discharge, likewise taking them down to 8% and then charging them full again and good chance i wont do it unless the cells ever look out of balance.
     
  15. skeeter

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    I can't seem to find the setting in the DJI Go app to set the auto discharge level to a specific point, eg., 60%, 50%, etc. Anybody know what screen it's on? (I see the screen to set the number of days to auto-discharge....)

    Thanks!
     
  16. flybid

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    You're not able to discharge it to a specific charge level. By default it takes it down to 50 or 60 I believe.
     
  17. msinger

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    It only auto discharges down to 65% (per DJI's battery guidelines).
     
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  18. skeeter

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    Thanks for the information and the guidelines PDF file.

    I guess I've never seen it immediately after it's finished the auto discharge. I checked on my battery is about three weeks after my last flight and both of them were down to about 10%. I wasn't sure if the auto discharge feature was taking it down that low or not.

    I'll pay closer attention to it this time around.

    Thanks!
     
  19. msinger

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    It won't. Your batteries will naturally continue to discharge over time though. If you're not going to fly for a while, press the battery button to check the level every couple of weeks. If the second light is blinking or not lighting up, then you should charge your battery until the 3rd lights starts blinking.
     
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  20. skeeter

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    Interesting. My non-intelligent batteries from my P2 do not exhibit this behavior. At least over a fairly short period of time...

    BTW... I'm running 1.4 firmware in the bird and batteries.