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Calibrating TB48 Batteries

Discussion in 'Inspire 1 Discussion' started by Kevin Cabral, May 20, 2016.

  1. Kevin Cabral

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    I'm hoping to get someone who can bring clarity to my issue. Basically I'm at charge 15 with a battery health of 96%. The first few charges to the battery I noticed the mAh total capacity was wrong, and read 5500 instead of 5700. So I tried to drain it down to 2% 3 times within the first 5 charges to the battery. It never helped. DJI advised to drain it completely until it shut off at charge 10. I did that, and now brought the health to 96%. However, the mAh didn't change much. Now I'm sitting at 5543 mAh. Should I be concerned at all? After charge 10, I've been easy on the battery and made sure to land my Inspire at 40% or 50%. Just sucks it's already at 96% health at 15 charges, what will 50 charges look like... 80% health? :( Has anyone else ran into this issue?
     
  2. Kevin Cabral

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    I just realized I made a thread of my topic, my apologizes. However, this will just be an 'update' of my situation. I just don't know if I should be concerned of it being 96% health at 15 charges. I think it's a little soon to be honest. Again, could of been because I hurt the battery to early in the cycles. Hopefully now that I've being easy on them not draining below 40%, it'll help.
     
  3. The Editor

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    Please use the search function on the forum - this has been discussed before
    See here - I Want My mah Back!
     
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  4. Kevin Cabral

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    I suppose, just depressing that it's degrading rather quickly. I assume not going lower than 30% on each charge should help the life a bit no?

    Also, when are these lipo batteries good till? Should I scrap these batteries when the health reaches 50%? Or can they last longer till 30% or even 0% health?
     
  5. The Editor

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    I have twelve batteries and I fly them all to around 3.48-3.50v (lowest cell) under load - I don't really take any notice of the percentage fuel gauge as it's pretty meaningless.
    Flying down to this level on the packs means they recover back to around 3.7v per cell or just over when the load is removed. This is perfect for them and not over stretching them.
    You DO NOT want to be flying lower than 3.45v as this gets into close range of the drop off plateau of lipos which is usually around 3.3-3.5v. I don't want to be anywhere near there!
    As an aside, if you check your fuel guage when you are down to these voltages you will probably find it is around 17-18% but using the voltage method is much more accurate than a programmed percentage meter that needs calibrating every five minutes.
    Using packs this way (Never flying below 3.45v, making sure they recover to 3.7v, allowing them to fully cool before recharging etc) will mean you are treating your batteries the best you can.
    Also, if you are not going to be flying even for a couple of days, put them at storage charge (around 3.86v per cell) and charge them from there next time you need them.
     
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  6. Kevin Cabral

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    Very informative. I really appreciate your help. I'll take your advice and monitor the voltages instead of the %. I'll make sure to fly above 3.48 before landing, obviously land before reaching 3.45. I do notice the battery jumps to 3.7 or 3.8 depending after the motor's turn off.

    Again thank you! :)
     
  7. The Editor

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    Yes, you don't want to be 100m out when you are down to 3.5v or so.
    You want to be back at your landing point ideally and hovering for the last 20 or 30 seconds really.
    All packs will vary slightly but the 'magic figure' you are looking for is 3.7v or higher recovery after you land.
    You can even watch the cells on the battery screen for a few seconds after landing and make sure they climb above the 3.7v level.
    I normally, land and monitor each cell to make sure every one of them creeps to 3.7v. As soon as I see all cells have recovered (and they will continue to creep up even after you remove the pack and put it aside) to this level then I power down and then swap packs over ready for the next flight. :)
     
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  8. Kevin Cabral

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    Good to know :) If it doesn't reach 3.7v, I assume it's time for a calibration? Do you recommend draining the packs until they shut off completely? That's what DJI told me to do for my 2 batteries because the mAh wasn't reading accurately. Now they read it accurately, but knowing I drained them 3 times to 2%, I sort of hurt the packs :(. Again I'm just going easy on the packs for a bit haha. If it needs calibrating for instance, what's your trick to get to 3.3v? I tried to hover it at 0% when the packs were not reading the mAh accurately and the voltages read 3.4. Then landed it at 0% and waited till it died which was 3.25v. When I checked the battery history info, I noticed it gave me some 'cell protection' status. I assume when it died completely, there was a safety feature that kicked in.
     
  9. The Editor

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    Voltages are absolute, percentages are relative to however DJI has programmed them to show.

    No, calibrating will not change the rebound ability of a pack.
    Recalibration, does nothing more then 'tell' the battery logic what is 'empty' and what is 'full' so it can display a percentage. It really is a simple as that. Thats the whole reason percentages are pretty useless, because they need recalibrating and have to take into account the aging of the pack etc by using a conservative algorithm.
    If your packs are not bouncing back to 3.7v then you are either flying them too low or they are aging and not recovering as well as when they were newer.
    With new packs,their internal resistance is very low (which is good) and means they do not drop that much under load. However, as you use them and as they age the internal resistance of the cells increases and a larger voltage drop is seen when you apply load (flying) to them. They will also not 'bounce back' so readily after use. This doesn't mean they are useless, it just means their efficiency has dropped and you will get shorter flight times from them.
    Only you will be able to judge when you consider a pack should be retired - when you get only 8 mins useful flight time? Maybe more, maybe less - your choice.
     
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  10. Kevin Cabral

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    You have so much knowledge in these lipo batteries it's insane. I had to pick your brain with my previous question, so don't mind me :) Again, I appreciate you taking the time in helping me out with my concerns. Going to bookmark this thread so I can refresh my mind when needed :). For the time being, I will monitor the voltages and keep them above 3.45 on load and watch how they recover. I'm sure my 2 packs will be fine and recover to 3.7v for a few months, unless I beat them up. Thinking of getting a 3rd TB48 sometime soon. :)
     
  11. The Editor

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    I am always conservative when I have anything in the air (and that includes my arms at an auction :p) so until you get comfortable using this method and seeing exactly how your packs behave I would land at around 3.5v (lowest cell) or just above (3.52-3.53v).
     
  12. Kevin Cabral

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    Will do. Thanks a ton! :)