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Battery Charging - Performance Tips

Discussion in 'Inspire 1 Discussion' started by GizaDog, Jan 16, 2015.

  1. GizaDog

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    I've been in the game for a while and always thought its best to let batteries cool for before recharging them. Does anyone have other tips in making these batteries last and perform at their best?
     
  2. Quadpilot

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    Have you read the Intelligent Flight Battery Safety Guidelines from DJI? Lips hate the cold. Do not store them at less than normal room temps. Set to auto-discharge after a certain amount of days in the app if you leave them fully charged.
     
  3. Eliran

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    One thing that is a must is to cool the lipo pack prior to recharge it. It means (for durability purposes) that 3 lipo packs will last more than use 1 pack then another one and then the last one.

    Lithium polymer can't handle very well recharges while it's hot or warm.
     
  4. The Editor

    The Editor Moderator
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    Sorry but this is VERY VERY wrong! If you are storing your Lipos for a prolonged period the absolute best environment for them is a colder storage - A fridge is ideal. You do not need to store them this way if you are going to use them again in a few days but for prolonged storage - say longer than 3 weeks cold is better to prolong their life.
    Perfect conditions would be at around 3.86v per cell at approx 4 degrees. DJI packs are nothing special in the Lipo world and rely on a chemical reaction to release their energy the same as every other pack.
    Packs degrade over time whether they are being utilized or not but if you want to slow down that degrading process then the best way to store them is as I stated above. However, the caveat being is you MUST bring them back up to room temp BEFORE charging.
    Stores in this way your pack will only lose circa 2 - 6% of their capacity over a 12 month period. Storing Lipos in a warm environment can mean they lose up to 30% of their original capacity in a year! That means your 4,500mAh pack is only going to give you 3,150mAh and then you should only fly to 80% of that which mean 2,520mAh !

    Also... yes, you should allow your packs to cool back down to ambient temp after a flight before you recharge them. Charging warm packs is not good for them.

    I've actually posted on another thread here http://www.inspirepilots.com/threads/lipo-discharge-threshold.707/
    as I'm curious to know how DJI have set their discharge/empty levels for their packs.
     
    #4 The Editor, Jan 25, 2015
    Last edited: Jan 25, 2015
    jon b, lrwskyfilms and Eliran like this.
  5. Eliran

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    The Editor, you should make your bove post as FIXED since all you've stated is just true.
     
    Wiski23 likes this.
  6. Jre

    Jre

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    Does anyone know...

    If I fly one weekend and bring a battery down to 10-30%, and I'm not going to fly for another few days or until the next weekend, should I:

    1. Recharge the battery the same day I drained it.
    2. Recharge the battery the day before, or on the day that I fly it next.
    3. Doesn't really matter.

    Edit: Also just read the following in the battery safety guidelines document:

    "Do not charge the Intelligent Flight Battery and remote controller at the same time, otherwise the charger may overheat."

    Um, pretty sure that this is a direct contradiction to their official "Setting It Up" tutorial video where they charge the controller and the battery at the same time. And if you're really not supposed to, they should have just had separate chargers, instead of the pigtail charger.
     
    #6 Jre, Feb 19, 2015
    Last edited: Feb 19, 2015
  7. blade strike

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    Correct, but you never want to store a charged lipo in the cold. But a lipo at storage level loves the cold, just don't ask it to produce power:)
     
  8. MostlyBonkers

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    Some good info here. 40-50% state of charge is best for storage. That's why you'll find all gadgets with LiPo batteries have about half a charge when you take them out of the box.

    I would put money on DJI making the 0% state of charge that the user sees as a little above the minimum safe voltage for each cell. That way, you get the maximum possible flight time without taking the risk of bricking the battery. In other words, the user can safely discharge to 0% and even get away with not charging the battery for a week or two before the cells drop below their minimum threshold and the protection circuitry prevents charging.

    It's the difference between the quoted capacity and the nominal or useable capacity.

    You do put the battery under more stress by discharging it to it's minimum nominal capacity, but as long as you charge it to 40-50% within a day or two, I wouldn't worry about it.

    That's why DJI allow you to adjust the alert thresholds. The default is about new users getting their machine back even if they haven't paid attention. For experienced pilots that feel comfortable setting a low minimum threshold, then do so to get those extra few minutes of flight time.

    The batteries are engineered to take a full discharge, just like your mobile phone is. With an expensive quadcopter, it's more about whether your nerves can!
     
  9. MostlyBonkers

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    Just in case some of you are interested, I wrote this article for a different forum:

    http://www.electricmotorcycleforum.com/boards/index.php?topic=4280

    A good place to get more info is here:

    http://batteryuniversity.com

    I can recommend reading the book if you are really interested in the subject. For the majority of people, my message is that it's worth considering the storage charge, but most of all just get out and use the damn thing at your convenience. The engineers have done the worrying for us so make the most of it before you lose interest, or lose the drone.

    As it happens, I lost my Phantom 2 today after six weeks of ownership...
     
    #9 MostlyBonkers, Feb 21, 2015
    Last edited: Feb 21, 2015
  10. mdomeny

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    my question would be if it would be possible to cbarge the batteries at the rate of 1C... the camharger supplied only has an output of 3.87A at 100w... 90 mins for the smaller battery and about 2 or more for the 5700mhA... if i'd get an adapter with sam spec only at 5A output would i break something?
    any thoughts...
    charging at 1C (is the A of the battery, so here it woukd be either 4800mhA or 5700 mhA for the dji batteries) is safe for what i konw. in my case at the moment i would be faster off with charging and would not have to wait months for the second charger to arrive in the shop but buy an adaptor put on the same cables and connectors and just charge happiely ever after... :)
    i was wondering since the batts have their own electronics i (in theory) could not damage anything... or?

    m
     
    #10 mdomeny, Mar 6, 2015
    Last edited: Mar 8, 2015
  11. MostlyBonkers

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    Good question. It's worth taking a look at the Inspire 1 tech specs on DJI's website. There they say that the max charging power for both batteries is 180W. As their charger outputs at 26.3 Volts, this implies that you can charge their batteries at up to 6.84 Amps. However, don't be fooled into thinking that would lead to a charge time of 33 minutes for the standard battery or 43 minutes for the larger one. Once the cells reach their maximum voltage, the current draw reduces until it reaches a minimum defined level that indicates a full charge. This is why the stock charger, rated at 100W, still takes 90 minutes to charge the standard 100Wh battery.

    If you are able to configure a power supply to deliver 26.3V at 6.8A then I would estimate the charge time would drop to 45-50m for the standard battery. Perhaps an hour for the larger one.

    In fact the standard charger will be charging the standard battery at 1C until the current drawn reduces towards the end of the cycle. If you stop charging after about 50 minutes to an hour you'll probably find you have reached 90% capacity.

    So why don't DJI provide a 180W power supply to charge the batteries? IMHO they are also trying to optimize the number of charge cycles they can get from the battery before it drops to 80% health. I also think they don't want to exceed a 1C continuous charge rate for the same reason.

    I strongly suspect that most people will never get anywhere close to cycling their batteries 2-300 times because they just won't get out and fly their drones often enough. I don't think that charging at 180W would shorten the battery's useful life significantly either. Therefore it's likely to have more to do with the increased cost of producing a higher output charger and dealing with the extra heat it would produce. Engineers like to err on the side of caution too.

    I hope that helps.
     
  12. Kilrah

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    To not damage anything you must use a power supply with adjustable voltage set to the same as your original DJI charger, AND an adjustable current limit that you set to the maximum the battery is rated for (mandatory).
     
  13. mdomeny

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    i wouldn't want to charge over 1C so for the big pack a max of 5A and for the smaller ones if would be able to get a power adaptor with 4700mhA output at still 100w would be good i think. it would still take down chargetime a bit. no??
     
  14. Kilrah

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    100W is already what the stock charger supplies. That results in about 4.3A, current-limited.
     
  15. mdomeny

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    ok. maybe i am getting something wrong here, why does it say 3.8amp output on the back??
    how can it supply the 4. something you are saying?
    just asking.
     
  16. Kilrah

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    Because there's some tolerance? Seems to vary a bit form one unit to another as some mentioned their charger got quite hot and others not. I measured mine at 4.3A.
     
  17. mdomeny

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    i see... mine got warm when csarging both transmitter and batt but putting it on some metal or something to absorb the heat it seems to be ok. i am still waiting for the other charger to arrive and that is why i am asking and was looking for an alternative. i was just not sure wether i would brick something in the batt electronics when charging at 5amp for the big ones... if not i will make a charger with an adaptor that will go on 26.3V at 5A... and only use it for the big packs.
     
  18. Kilrah

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    The maximum charge power the batteries support are conveniently listed in the Inspire manual.
     
  19. mdomeny

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    thx 4 the info. will have another read through.
     
  20. BlueSkies

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    When I fly and want to setup the battery for storage, I fly until 23.3v and land at 23.1v. That puts the 6 cells at 3.85 volts. Perfect for storage.

    BlueSkies