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Tested batteries for fast dropping down in voltage

Discussion in 'News' started by huppe, Jun 27, 2015.

  1. huppe

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    Because I wasn't able to fly for 2 weeks I have tested all 7 batteries because they were discharged to 50%.
    6 TB 48 and 1 TB 47 were tested.
    Tested all batteries 5mtr(20ft) away from me and about 3mtr(10ft) altitude.And I was surprised that ALL batteries came at a point to go down from about 40% to less then 10% in a few seconds!
    So this makes me clear that you always charge batteries to 100%!
    It has said here before on more threads,and I go out with all batteries at 100%,but I was surprised with the result.
     
  2. Ward Paterson

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    Storing lipo's at 50% is the right thing to do. The problem lies with how DJI determine capacity in their bullshit software. Do not store lipos at 100%. The likelihood of doing more damage at peak voltage is higher than storing at 50%.

    However, yes, definitely charge to 100% before flying. Also worth while monitoring how long it takes for the batteries to charge from 50%. If it only takes a few minutes, there is a problem!
     
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  3. John Alan

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    Interesting... thanks for testing that out... I figured that would happen... :oops:

    I have changed my battery workflow in the last month or so based on all the info floating around now... o_O
    Batteries are kept at 40-60% range when not in use...
    Night before flying... I decide how many to charge (based on my intentions)
    I first just do a 'plug in, battery off' charge to bring it up to 95%+ range... (I do not turn on the battery, just plug in charger)
    Once it stops (lights go off)... I set it aside till all batteries I intend to use are up to that level...
    I then do a 2nd round with the batteries turned on first... this then truly tops it up to a 100% fully charged level...
    When I get to my flying range... I use a battery I left at 50-60% to extend gear and check over bird is ready to fly... (uses < 5%)
    Swap in a 100% battery... boot it up... check cells and verify it's truly fully charged...
    Run down my checklist (sensors, etc) while it sits on the pad powered up ready to go... (I get a better GPS fix I find)
    <Now this next part is my opinion and up to you how much you want to push it>
    Fly it down to under 50% at minimum... be somewhere around home point when I hit 40%...
    I'm working on landing by 30%... If I go under 20% indicated, then I pushed it too far in my mind...
    <end opinion>
    I check the battery health and cell voltages before turning it off.. part of my post flight checklist...
    Let it cool a bit... If I pushed it under 40% I then put in on a charger right away to get it back above 40% asap
    (I had one TB47 brick before the last FW push... which addressed this issue... they say)
    Then back in the box at 40-60% till next time...

    I'm not claiming this workflow is right or wrong... good or bad... :confused:
    Just stating for the record what I do these days... in the hope it may help someone else learning about I1 batteries... ;)
     
  4. ajohnsonlaird

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    John: I don't know enough about the I1's batteries to say this is unnecessary, but I was just curious how you found out that charging the batteries when they're powered off does not take them up to 100%?

    Just curious why you don't use one of the fully charged batteries here? Again, my question is based on my ignorance... :)

    Andy
     
  5. ajohnsonlaird

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    Is the problem that the I1 batteries are inherently flakey or is it more that, when you first power on the I1 it "calibrates" the battery and thinks that it's fully charged when it really isn't?

    This "40% to 4%" sudden discharge problem sounds really worrisome -- so I guess I'm asking is the problem with the batteries, or with the fact that if you put a battery in that's only charged to 40%, then the firmware gets "confused" (that's the polite word for it)?
     
  6. John Alan

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    No such thing as a bad question... I'm happy to explain my why's... ;)

    I have 6 active batts... 4-48's and 2-47s... typically fly only on the weekends... they sit at ~50% all week...

    I have found that batteries charged once from an off state on a Friday night will only show 95 to 97% the next day when put in service...
    Doing the off, then on, double charge has yielded 100% full the next day every time for me... <shrug>

    As to the other question... no reason other then to drain a battery I left over 50% down closer to 50% for it's week off to come... ;)
    I'm then also powering on a battery at 100% and leaving it powered on till drained after flight...
    That may be a bit silly but anymore... you can't be too careful...


    And to help - as to your next posting... the issue is with the board on the battery getting confused...
    Huppe has shown (at top) a repeatable fault mode...
    If you start at 50% indicated and had been left a while like that...
    It will drain to 40% then fail quickly to under 10% indicated...
    If the board thinks your down to 10%... it sends a signal to the bird to land here... now... :eek:
    That can get ugly in a hurry... :(
    If you turn it off and back on it will show like 30+%... based on cell volts...

    The issue is... state of charge can be determined from a battery at rest by cell voltage...
    But a LIPo under heavy load... that does not work... so it works off capacity minus current...
    The board is getting confused not starting from 100% full and calculates wrong while draining.

    I hope this helps and answers your questions... :)
     
    #6 John Alan, Jun 28, 2015
    Last edited: Jun 28, 2015
  7. SultanGris

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    The only way I've found to fix this error is leave the battery in the inspire with it powered on until it shuts itself off. It will stay powered on while reading 0% for 20 min or more because the reading is off. Then when you fully charge them again the problem will be fixed until they discharge themselves to 60% automatically if you don't use them for a while. Their firmware is definitely wack. As long as I use my batteries every day they don't have this issue, only after their bs auto discharge happens will it occur. If I fly a battery down to 60% or any other percentage and power off and then later the same day use that battery again down to 20-30 % which is my Normal level I take them down to they perform normally without issue.
     
  8. huppe

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    I always store my batteries at 50%.Check the forecast for the next day and charge them when I go out.This time I had charged them for a fligh,but due to the "no signal error"I was forced to stop and brought the Inspire back to my dealer.So that is why all my batteries were down to 50%.After the repair I was going to test everything so that was why I tested the batteries also.
    Conclusion is clear:never fly when batteries are not fully charged!
     
  9. mdomeny

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    could someone define "store" batteries... what time interval does this incoperate?
    1 week of no flying or 1 day...
    i have used to have mine charged to be availabe when i need to go (sometimes it goes fast for me) so i don not or would not have time to charge them up from 50%...

    thank for any info and sorry for the dumb question... :)
     
  10. huppe

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    As far as for me when I come back and I know that flying isn't there for the next day (or more) I charge my batteries to 50%.This takes about 40 minutes so after this unplug them.So no matter what happens even in a hurry I fully charge them when I go out.I know it can be painfull when you see wheather is great and you want to go out,but losing or damaging the Inspire hurts more!
     
  11. sirnikolas

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    I've just discharged one of my batteries to 0% as it's just hit it's 20th cycle. My question is, should I now charge it to 100% or do I charge it to 50%? I won't be flying her until this weekend or perhaps the next.
    Thanks.
     
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  12. John Alan

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    Hmmmm... I'm not sure... :oops:
    And now that DJI's server is down... can't look it up... :p
    My gut says you need to do a 0 to 100% recharge in one shot to reset the total mAh capacity number on the board..
    BUT... I'm not sure on that... :confused:

    On edit... Oh look, the battery manual can still be downloaded...
    It states full charge... does not say all at once or two steps is ok however... <shrug>
     
    #12 John Alan, Jun 28, 2015
    Last edited: Jun 28, 2015
  13. Kilrah

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    I would charge fully now. Makes most sense to make it learn the "empty" and "full" points together.

    As an extension I only do the full discharge when I know I'm going to charge and use the battery straight away. The whole point of it is to calibrate the meter that can have drifted when sitting unused, makes no sense calibrating then precisely let it sit again.
     
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  14. ajohnsonlaird

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    That makes sense -- I think two things might be happening:
    1. There is a certain amount of "rebound" -- the battery signals it's been charged to 100%, but when you disconnect it from the charger, the voltage settles back a bit. This could also be caused by the battery's internal temperature after charging being a bit warmer than ambient.

    2. When you do the second charge, with the battery at 95% or so, it might charge at a lower rate. There's been discussion on the Freefly forum that lower charge rates increase the total amount of charge we can get into a LiPo. Also, this second charge takes place with the internal temp of the battery at ambient temperature and, because the second charge is shorter duration, the battery will not heat up as much.

    Yeah. Makes sense. Not much makes sense these days, but this does! :)

    That seems prudent.

    It would seem to make better sense for the I1's firmware to make its initial calculations of battery level prior to motor start so that the load is much lighter on the battery and there's no voltage sag caused by the much higher load once the copter's airborne.

    Alternatively, the "intelligent" battery should be communicating its "no load" voltage and/or the number of milliamp hours already discharged -- there's obviously some electronics left powered on at all times, so it would be pretty easy to approximate how many mAH were injected during charging and how many mAH were consumed thus far.

    I fret whenever I see any electronics with "intelligent" or "smart" in its name! :)

    Do you guys see the "40% to 4%" problem if you do two flights on the same battery -- the first that drops the battery from 100% (say) to 40%, then you power off the copter but leave the same battery in, and then power it up (at 40%) for the second flight?

    Or does the problem only occur when you *change* to a "new" battery that happens to be at 40% charge? That seems to be what huppe was referring to. For some reason, my geek instincts say this would seem more likely to cause the problem but the first example (two flights on same battery with intermediary power cycle) should not be a problem...but...

    It certainly helps -- for which thank you!
     
  15. Whodatdere

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    Does anyone else find it ridiculous that these batteries are apparently this flakey/finicky? I saw a post on the official forum that faulted the owner for taking off with a 95% charge and the battery doing the 40% to 5% instantly with a resulting crash. Dji's response was sorry your fault next time charge to 100% prior to takeoff. If that is the case the numbers are meaningless and the aircraft software should not let you start the motors with anything less than a hundred percent. It's similar to my fuel gauge reading 3/4 full yet I better not go anywhere because I could suddenly run out of gas with no warning on the freeway.
     
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  16. SultanGris

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    It doesn't matter if you fully charge it or not, the percentages get out of wack and aren't accurate if you allow it to self discharge it seems. I also had the problem once when I accidentally unplugged one before its lights went out and it was so close to charged it didn't charge further when I plugged it back in but in hindsight it may have been more the self discharge that caused the error rather than the premature unplugging.
     
  17. Phatzo

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    I used to take off with 98% close to 100% because of the charging error that is said here in the thread.. I just drained a battery to 0% (until it switched off) and put it on for charging turned on... I will check tomorrow and report back what the battery says if anyone is interested.

    m
     
  18. slim.slamma

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    Somebody said they took off with a 95% charge & they batt dropped to 40%?
    75% charge most def its gone drop
    85% who knows
    but 95, i seriously doubt that. Stop scaring the natives!
    Its possible people are taking off with the 5% discharge warning. Which states the battery could drop while in flight. Has anyone noticed that warning but in that case its
    pilot error
     
  19. SultanGris

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    Is charging them while they are turned on safe? I've never heard of such a thing. Any documentation from dji about it? Thanks
     
  20. Whodatdere

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    Nope here is the link to the thread. Read for yourself.

    http://forum.dji.com/forum.php?mod=viewthread&tid=19602

    Took off with 95 percent at 50 percent suddenly dropped to seven percent. His flight logs confirmed in thread by a dji rep, Autumn and Bruce. Bruce's response was should have not taken off at less than a full charge ie. 100 percent. So yes way and the natives should be cautious.