Battery warning :Turnigy nano-tech 8000mAh 6S 25~50C Lipo Pack

Discussion in 'Batteries & Power' started by Jay Pearl, Apr 2, 2016.

  1. Jay Pearl

    Jay Pearl New Member

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    Hi Guys just sharing what's happened to me today.I grab 4 x 8000mah 6s battery packs from hobby king to save some money.Checked Voltage on arrival and was fine.I charged and gone for flght test next day.I was flying them parallel and because It was new lipo pack for safety reason I done hoovering 2m above ground to check if they are fine.Voltage readings were good and then suddenly voltage drop and second level battery warning kick in.I managed to get close to ground when I lost motor power.Hard landing and just landing gear damaged.Checked voltage after that and booth batteries have low voltage cells around 2.70-2.90.Rest cells was around 3.80vI was lucky this time but never will buy this cheap lipos again.
     
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  2. Steve Maller

    Steve Maller UAV Grief Counselor

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    Wow...very lucky indeed.
    Sadly, the old expression "you get what you pay for" seems to always prove its wisdom.
     
  3. Jason Smoker

    Jason Smoker Active Member

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    Lucky!! I have used Turnigy nano-tech 6000mAh 4S 25~50C before on my old microkopter bird. When they decide to sag/ voltage drop they really meant it! Scary experience i wouldnt use them again ever
     
  4. Jay Pearl

    Jay Pearl New Member

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    Yep, lesson learned.Time to invest in Gens Ace.
     
  5. Jeff Camden

    Jeff Camden New Member

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    This happened to me with Gens Ace Tattu 10,000 25c in parallel, I had previously flown the batteries 12 times in single on a DJI S1000, without any sag, then on a flight with the ALTA voltage dropped out! Was 21.5V to 21V in about 10 seconds then under 19v in less than 30 seconds.
    What UAV were you flying Jay?
     
  6. Jay Pearl

    Jay Pearl New Member

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    Hi Jeff, I hope you manage to land safety.I was flying cinestar 8 with kopterworx kw10 motors.
    After this happened I bought better battery charger and monitoring my batteries more carefully.
     
  7. Cody Hanthorn

    Cody Hanthorn Member

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    Here is a questions though. On my other ship I am flying pixhawk. How much battery dip do you guys set your voltage at. I have my 4s setup at 13.5v. I flew for 5 minutes with 12ah drawing 47 amps. I have way more than 5 minutes when my pix told me its low voltage and went to RTL. I had set it there a a beginning setting. I see it had about a 1volt voltage drop while in the air. I understand the better packs will not have 'as much' voltage drop as the cheap ones, or perhaps old ones, but in the margin of safety after you land your packs will come back voltage wise some. So how much is acceptable? 13.5v in real time in the air, then it returns to 14.5v on the ground.

    Two years ago I ordered new packs for black Friday. One pack was good, but the other took like 3 hours to balance out. I cycled them on the charger and it came out of it. Nothing can be depended on anymore it seems.

    -Cody
     
  8. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Cody: I would ignore the voltage "rebound" after you land -- what really counts is the voltage under load.
    So when I see the voltage under load drop below 14.0, I'm heading home -- I'd rather than with spare electrons in the LiPo than was the voltage decaying and causing an uncontrolled descent.

    Just my $0.02. Actually, as I'm in Canada now that's actually only $0.018.

    Andy
     
  9. Cody Hanthorn

    Cody Hanthorn Member

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    Andy,

    Interesting. Since I have never had the option of looking at live voltage drop it leaves me in question with my large ship. I have always done a calculation with it, and the charger has confirmed that I am well within the margin of safety for what I take out. I wonder how many other guys that run the altas, and cinestars have live feedback and how they are operating.

    The oddity is that the packs internal resistance measures fine at near 5m ohms for one and near 0 for the other. The packs only suffer from age. I had always thought of it the same way like when we charge larger setups like 2 10ah batteries in parrallel the pack is not really at 4.35 voltage during charging. I agree with the load principal for safety reasons, but it literally means that the pack has diminished 50% of its capactiy in two short years, low cycles and stored at the storage voltage. I have heard of the 5% per year rule, but this blows that away. To me safety is paramount, but maybe I am missing something.

    Another friend is running 6s setup. I asked him and he said on his pixhawk he is nearing 3 volt drop from landing and in the air. I should clarify from him at what point is he getting this value.

    -Cody
     
  10. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I infer that you're not flying a FF copter then? :)

    Speaking only for myself, I couldn't live without knowing the voltage under load -- it seems to be a good proxy for the general behavior of the battery as well as an indirect measurement of the internal resistance -- which itself represents an important factor for the current supplying capability of the battery. But that's just my personal preferences. I do not really fixate on milliamps drawn out during flight or put back during charging -- maybe I should, but I confess I typically do not.

    This is typical of the kind of posting I see on the Internet -- I'm not sure of the science behind it, but it's typical nevertheless:


    a) Packs that are as good as new: between 0 and 5 milliOhm/cell
    b) Packs that have been used dozens of times, but still feeling fairly good: between 5 and 10 milliOhm/cell
    c) Packs that have been used even more, and start to feel weak: between 10 and 20 milliOhm/cell
    d) Packs that almost won't hold your heli in the air anymore: over 20-25 milliOhm/cell
    I'm not sure you're missing anything -- as you commented in your previous post, you cannot depend on anything any more -- which includes postings made by forum Administrators!

    The under load/no load voltage difference may be an important metric for battery health, but if it is I'm not sure I fully understand the science behind it. It certainly is a measure of internal resistance -- as one can see if you imagine (just imagine!) a battery with a dead short across it for a load -- the only thing that would limit the current flow would be the internal resistance of the battery and the wire connecting the two terminals. In that condition, the voltage drop across the battery would effectively be caused by the voltage drop across the internal resistance of the battery itself.

    Now repeat the thought experiment with say, a 100 ohm dummy load resistor and calculate the voltage drop across the terminals of the battery. The total resistance in the circuit is 100 ohms + internal resistance of the battery. Ohm law (V = iR) would tell you what the voltage drop should be when under load.

    I think the giant unknown here is the quality and consistency of LiPo batteries. I've had some El Cheapo Lipos flat-line on me after only a few dozen charge cycles. I had one Tattu that had leaked electrolyte when I received it and had never used it (Tattu promptly replaced it by the way, so I do not complain in the slightest about their customer service).

    But the bottom line, for me, is to monitor the under-load in-flight LiPo voltage. That seems to be a good metric of the state of the health of the system.

    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limitâ„¢
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  11. Cody Hanthorn

    Cody Hanthorn Member

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    "I infer that you're not flying a FF copter then?"

    If I could I would, but not all of us fly the cost of a new loaded Yukon in the air++. Its like a Dave Ramsey to financial flying. You know the snowball effect...We start with a go pro duct taped...then end up to aerial freedom to use whatever gear...

    No I think thats sound logic. There is a couple variables, and we could really go OCD on this. I always enjoy the people on this forum. I'll order some new batteries after I do a flight test tonight.
     
  12. Vic Peters

    Vic Peters New Member

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    Is it possible to screw up throttle settings or any other for that matter on a Pixhawk that could cause 2 different lipos 2 both drop 2v in a couple min. of hover? Or just bad luck with batteries 4s nano 6000mah and a floureon 5000mah(new)
     
  13. Cody Hanthorn

    Cody Hanthorn Member

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    Im not there yet as im really struggling to get the mini osd working. Several tries but no video or data from pixhawk inspite of serial connection settings with extra. What osd are you running? I know there is a pretty simple procedure fore getting the fredback accurate for voltage and current sensor. It corrects tge voltage fivider calculations. If I find it ill send it to you. My current draw is about 45 amps on 4s. I should be much better than 10 minutes off 10ah usable(6.6 x2). Im really pleased as its the first time I got 20 satilites. Compass is amazing.
     

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