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Some Observations about Phantom 2

Discussion in 'General Discussion' started by Case29247, Sep 14, 2015.

  1. Case29247

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    I've been flying a Phantom 2 with 2D gimbal and Hero 3 for about 1-1/2 years now. I've upgraded it with video downlink and Black Pearl monitor, iOSD, and have added copper foil shielding to the GPS antenna. All-in-all, I am very impressed with the system for the price. As somebody commented (I forget where), ten years ago some of the technology involved was probably a "state secret." :)

    Putting aside the fact that the design and construction of the P2 is "consumer grade" (you'd never put it in a "real aircraft), I think it's amazing. If anything, I have but one criticism that I wish DJI would address.

    It's the flight battery system.

    1. First, it's in the user manual's discussion about the "care and feeding" of the batteries. I think that it's utterly insufficient. In hindsight, it's mostly there in the manual, but it's not worded very well. It's not very complete. It's not emphasized. And there are some important, glaring omissions. If the "care and feeding" of these batteries is so important, then emphasize it and make it clear in the manual. If you give me the information, I'd be glad to write it in good English so you don't have to translate it from the Chinese.

    2. If it's so important to store these batteries in a partially charged state, then DJI should provide (or at least offer for sale) a charger/discharger. It's not sufficient to hint at things in the manual. Nor is it satisfactory to expect users to come back home with all their batteries discharged from flying, or to expect the user to discharge them properly by tethering the bird (or flying in the driveway) and running the motors.

    3. I know that there's some firmware upgrade that discharges these batteries automatically after about ten days, or whatever (Firmware which may or may not be buggy....I can't tell from reading a few threads. I learned that there was an upgrade, but it didn't work for some. Others said the Assistant didn't report the upgrade correctly. Others said the upgrade was withdrawn by DJI, ). Maybe somebody would be so kind as to tell me that I'm full of bunk if I am wrong. I think my four batteries, including one I bought about a month ago, don't have the auto-discharge feature.

    4. I have my doubts that the batteries report their state-of-charge and condition accurately all the time. I suspect that some additional work could be done in this respect.

    5. Look, I understand that these batteries are state-of-the-art, powerful, "smart", and lightweight, which should make them well-suited for flight batteries. But I'm starting to wonder if they're really all that well-suited for the task. I've used Sony Li-ion batteries in our video business for years, and never had a premature failure, or had to follow burdensome charging/storage routines. But then, they aren't Li-polymer batteries either. I just wonder if going to Li-ion battery construction isn't a better choice---maybe a tradeoff between some capacity and weight for a gain in durability. I dunno. I ain't an expert :)

    I'd appreciate some comments and insights.
     
  2. N017RW

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    LiPo is the only way [presently] to power electric aviation.
    Hands-down NQA. Everything else is too heavy.

    DJI has , as expected, selected the 'lowest bidder'.
    The intelligent portion has insulated the casual user from many of the pit-falls of their use except as you pointed out a good storage level solution.

    The BIG difference is the way these are used as in comparison to your Sony examples... these batts. are asked to deliver high-current for extended times with peak current many times their capacity.
     
    #2 N017RW, Sep 14, 2015
    Last edited: Sep 14, 2015
  3. LuvMyTJ

    LuvMyTJ ADMINISTRATOR
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    I find the auto discharge these 'smart batteries' use works very well for me.
     
    dirkclod likes this.
  4. JoeSchmoe

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    To 'Pile on' to the OP's battery Comments...

    After happily flying my two 120+ cycle batteries without incident... I came here, to Phantom pilots..after a long absence.. and suddenly lost confidence in my 'old batteries' and got a new one. (stock phantom 2 battery for 120.00) and heres what I found...

    My P2V+ flies WAY,WAY,WAY, better. With the new battery.

    It's way faster.
    It acquires more satellites, quicker.. when flying from the same spot.
    It displays more minutes of the (fuel guage bar graph)
    it's more quiet?/has a different sound
    and it has increased range....

    Its funny..because until I got this new battery, I hadnt noticed any change really... kinda like watching a dog grow...
    Now Im afraid to fly .. my two old batteries...
     
  5. Case29247

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    Thanks, folks, for the feedback.

    A lot of good points. For instance, there's no doubt that LiPo batteries are best-suited for the application in most respects. Light weight, large capacity and high discharge rate being three of them.

    I made the comparison to my Sony NP-950 Li-ion batteries only because I have enjoyed such a good history using them (since 1999, I've bought about 35), having experienced long life and capacity without the woes of having to jump through hoops to properly "care and feed" them. I just put a DJI battery and a Sony NP-950 InfoLithium battery on a scale to compare the weights, and performed the calculation about weight v. nameplate capacity. Sure enough, the DJI LiPo batteries have a significant weight-to-capacity advantage over the Sony Li-ion batteries (6.5g/w-hr. vs. 8.8g/w-hr, respectively)

    That is 35% advantage with LiPo., based on weight-to-nameplate capacity, and I'll admit, more than I expected. Of course, that's nameplate capacity, which may or may not really represent "reality" over the life of the batteries. That is, if the practical operational life of any battery is short, or quickly degrades due to "care and feeding" issues (or whatever).....Well, maybe this simple weight-to-nameplate capacity comparison isn't the whole story.

    In direct contrast to my history with Sony Li-ion batteries, my experience has been quite unsatisfactory with DJI P2 LiPo batteries. I have four...two that I got at the same time as I bought the P2 about a year and a half ago; a third purchased soon thereafter; and a fourth purchased about a month ago.

    My usage of the P2 has been generally this: Flew a lot in the beginning, but it tapered off after a month or so as the novelty wore off. After that, I have flown it sporadically for pleasure and work. I have tended to charge up the batteries that I expected to need for an outing. Thus, usually, I come home with batteries that have been discharged by use, but just as often I also come home with one or more batteries still fully or nearly fully charged.

    I devised a strategy in which I rotated them. For instance, one time I'd use them in 1-2-3 order, and the next time in 3-2-1 order (these days, the same with four batteries). When I thought I'd only need one battery, I selected any one that already had a full charge, charged others according to what I anticipated I'd need, and left any remaining in whatever charge they were in. Etc. In other words, I tried to even up the usage between batteries, and minimize storing charged batteries. It was not a precise strategy, but I thought it might help the overall situation.

    When I realized this was not enough, I started discharging fully charged batteries before storage. One thing I never did was just run the batteries down with the P2 motors. I did hook up a 50W halogen car lamp to some leads, and started discharging the batteries through the lamp when I anticipated a long period of non-use. It was a pain, and I had to be careful not to over-discharge them.

    So, what's the results. Not very good, I'm afraid. Batteries 1 and 2 are definitely swelled. Battery 1 was being used in my "Lost In A Bean Field" incident the other day. I suspect Battery 1 just ran our of juice, even though it was reporting okay. This is not the first time I've experienced a loss-of-power forced landing from a prematurely fading battery. And I'm sure it will not be the last.

    So, Batteries 1 and 2 are swelled somewhat. Battery 3 a tiny, tiny bit swelled. The newest, Battery 4, is solid. The Assistant software and blinking light system on all the batteries report that all is well.

    Here's the bottom line in my engineer's mind. I'll concede that LiPo batteries are superior for the application in terms of capacity and weight. However, DJI has failed its customers in two important ways.

    1, DJI failed to emphasize the "care and feeding" of these batteries in the manual (That's right, I actually read manuals...I read a lot!). DJI needs to do more.

    2. DJI failed to provide an adequate charger with the P2. It should be capable of charging AND discharging the batteries (Like in the NiCad days, good chargers discharged the batteries before charging them). Or at the very least, they should provide or offer for sale a discharging device certified to work with their batteries.

    I ordered a $25 discharger off eBay the other day. If and when I get it, I'll let you know what I think of it.
     
  6. vgt

    vgt

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    I store my batteries full, all the time. They're still >90% life, and haven't lost a beat since new. About nine months old, now.
     
  7. JoeSchmoe

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    I think .. there is "No formula" Between the % of life remaining assistant software reports, and any factors .. other than the number of times assistant thinks its been charged..
     
  8. Case29247

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    Like I said before, based on my experience with my many Sony Infolithium Li-ion camcorder batteries, I too started out charging my DJI batteries and storing them fully charged. After all, I reasoned, Li-ion and LiPo batteries are basically the same chemistry. I know now that it's in the construction that apparently makes a difference.

    I had no problems initially, but then after about forty cycles on each, I noticed some swelling taking place. Familiarizing myself with the relative merits of the two technologies, I discovered that LiPo batteries swell because of internal pressure that cannot be resisted by their lighter, weaker, thin film polymer container and internals. I think the same thing probably happens with Li-ion batteries, but their stronger construction resists distortion of the enclosure and internals. Anyway, that's my take on things. My understanding and a buck will get you a coffee at Micky-D's.

    Then I started consciously trying to store them in partially discharged states. One battery has failed completely, and I think a couple more are on their way out.

    I wonder if my charger could be a problem. Perhaps it's overcharging the batteries. Or maybe I'm expecting too much. Light weight, high capacity and discharge rate, AND life. Choose any two.....
     
  9. Fyod

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    IMO the original batteries have an insufficient discharge rate. They were probably very cheap and there is no justification to the triple price of a brand name 30C lipo.
    You can get 30C, 65C, up to around 120C 11.1V batteries for less. And with those discharge rates, there's no way you could ruin them with the Phantom within 50 cycles as many have reported. The thing that kills lipo batts the quickest is long high-burst discharges when you use a battery with insufficient discharge rate.
    That's why, as mentioned above, a new battery "feels" better. A new one has minimal internal resistance. The more you do burst discharges (full throttle up, flying in wind), the faster it'll kill a battery that can't take it. The result is higher internal resistance, later voltage drooping and pack swelling.

    I also believe that the voltage drops can cause all kinds of problems in the various electronics. In my case, the voltage problems caused the GoPro to repeatably stop recording and resulted in SD errors. I have since tested the GoPro with the same card thoroughly out of the Phantom to negate problems in the GoPro or SD themselves.

    I think it is extremely irresponsible for DJI to sell insufficiently designed batteries, putting anyone on the ground in risk, making the operator responsible, all while instilling what is basically a DRM to prevent owners from installing brand-name batteries made by companies that have decades of experience. The fact that they cost a third of the DJI's price is just a cherry on top.
     
    #9 Fyod, Sep 20, 2015
    Last edited: Sep 20, 2015
  10. Case29247

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    I had the GoPro "error" problems yesterday while trying to video a scene for a piece I'm producing--the GoPro constantly shut down with file error message. No video actually ever recorded, although I did get a few photos before each shutdown. I've had that experience a couple of times in the past.

    I think the best insurance against the GoPro shut-down problem is to make sure your GoPro battery is separately fully charged when you go out to fly. The GoPro may be mainly powered by the flight battery, but its own battery probably acts as a buffer between the GoPro and the ups and downs of the flight battery. And I know...I know..."Ehhh Gads! Another battery to charge."

    I've also experienced the GoPro "freeze-up" problem. I think it's also related to the GoPro battery state of charge. Since the only way to unfreeze the GoPro is to remove the battery, I've been tempted to do away with the DJI GoPro mounting yoke (with its two little screws--very inconvenient to remove in the field) and replace it with a Velcro strip-tie to make things easier. But I haven't quite gotten up the nerve to do it yet.

    ---------------------------------------------------------------------------------------------------------------------------

    As for DJI battery issues. I'm sure that DJI knows of their shortcomings, and like every for-profit manufacturer, they weigh fixing the issues against a host of factors, such as the price customers are willing to pay, the age-old razor and razor blade metaphor (cheap razors to get the initial sale, but expensive razor blades where the real money is), revenues generated by replacements (which can be considerable and important to the bottom line), planned obsolescence, etc.

    I would like to think it's the price problem here--that is, DJI knows most of their customers' final buying decisions are made to a great extent (many mainly) on price, and one or two hundred dollars lower means many more sales that would never happen if the price were higher for better batteries and overall quality. It's just the way human nature is...a buck or two can mean a sale or a no-sale.

    Still, I wish DJI would offer those of us willing to pay somewhat more the option of buying quality and reliability. I'd actually be eager to buy a charger-discharger and batteries that actually lasted one or two hundred cycles, even if it added 25% to the cost of the system.
     
    #10 Case29247, Sep 21, 2015
    Last edited: Sep 21, 2015
  11. Fyod

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    I forgot to mention that I always charge my GoPro as to not discharge the P2 battery (although it would be a couple mA). I'm almost certain it was due to the sloppy P2 battery, but not willing to try and replicate it. It recorded until I took off (photo+video mode). Atleast I had some kind of warning that something was wrong which made me concentrate on iOSD battery info and not fly far.

    I too would be willing to pay a premium for better batteries, but if DJI sold them, they would indirectly admit that the ones being sold now are inferior.
    I have no idea if the problems persist in P3 and Inspire models, but according to gathered data, it seems that the newer P2 batteries (square smart connectors) are worse quality than the old ones. The differences between battery life for different users is also a tell-tale sign of possibly B-grade batteries. I have bought over thirty Zippy 7S 5000mAh packs for a different purpose and none of them have failed or shown high resistance with over 50 cycles.
    I have to figure out how to refurb a P2 battery with Turnigy or Zippy packs.
     
    #11 Fyod, Sep 21, 2015
    Last edited: Sep 21, 2015