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Some advice on battery warnings

Discussion in 'Phantom FC40 Discussion' started by vonsworld, Aug 4, 2014.

  1. vonsworld

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    I've recently bought the FC40 and would like some advice on Battery warnings.

    Behind my house runs a quiet railway line in a cutting and behind that open fields, so I could make some good flights straight from my back garden without getting too near other houses. However I'm concerned that if the FC40 runs out of power on the way home it might end up landing on the railway line with a train coming! :?

    When you get the first level battery warning, how long is it before the second level warning is triggered and the FC40 starts to auto land?

    Also after the second level warning I understand you can still fly the FC40 but the left stick is reduced to the 90% position. If you continue to fly, how much time is there before the battery completely runs out? Would 2 minutes be a good guess?

    (I know that ideally the battery should not be discharged below 80%, so running it flat would damage it. However in an emergency this is better than losing the quadcopter).

    Finally could anyone recommend a digital timer to attach to the transmitter or a way of monitoring battery power in real time?

    Thanks :)
     
  2. lake_flyer

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    That's the question we all would like to be answered :)

    It is not a simple answer. It all depends on the conditions, wind, your flying attitude, GPS mode or Atti mode?, how did you set the levels in Naza, what battery do you use, total weight of the quad, size, material and twist of propellors.........

    I timed various situations with a stopwatch. how long does it take to do a RTH procedure from 100 meters up and 200 meters away, for instance. How long can it fly after the first warning (not just hovering but active flying)? Just time it until it starts auto landing. And time it again after you made any changes to the quad (weight as well as gain settings).

    Default I guess it is about 1.5 minutes max from first warning to actual landing. If you get a Lipo checker (2 bucks on eBay) you can set it to a safe level so you get a loud buzzer (audible from hundreds of meters) warning with time enough to return. I have mine set up to buzz about 1 minute before the first warning light.

    Generally, I hit the RTH switch when I hear the buzzer and switch back to GPS as soon as it is over my head (or over the home position), to commence a quick landing. You want to land quickly with the buzzing as it is really loud and annoying. It takes the Phantom less than half a minute to fly back from 300m distance. The landing is a different thing, it seems like forever when you have to get down from 200 meters high. I would say, generally, I would keep a fail safe time of at least 3 minutes before everything shuts down. That way you have time enough to RTH from a distance of 500m and about 100m up. And don't forget that you never know if you noticed the warning first time, maybe you missed the first 30 seconds, who knows.

    So best thing to do is to time everything in your own situation, experiment with voltage settings in Naza (know what you're doing and inform yourself, there's a lot to find on the subject on this forum, just don't set the second level lower than what is recommended for your specific Lipo, generally 3.3V per cell) and get a Lipo alarm or time every flight with a timer. Don't fly to high. Going down safely is taking a lot of time from high altitude. On a controlled fly back, lower the altitude gently during the way back. Give yourself an extra minute for safety, just to be sure, and set your timer or alarm well ahead of the actual deadline.

    I was a bit paranoid about batteries in the beginning. But since I fly with 2 2200 Lipo's I have redundancy in power (can loose a cell if it ever happens, and it happens, believe me) and it just flies a lot more steady, better balanced. I get 14 minutes until the buzzer with stock props, a gopro (no gimbal) and the FC40 cam with two stock Lipo's. After the buzzer I still have about 2 minutes to bring it in, which is always enough since I set my 'control box' in Naza to 200m distance and 100m height.
     
  3. lake_flyer

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  4. vonsworld

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    Many thanks for your reply with is really helpful, I've ordered a LiPo alarm from Ebay.

    My FC40 has the default voltage settings in Naza which are

    First Level
    No Load 11.3
    Loaded 10.7

    Second Level
    No Load 11.2
    Loaded 10.6

    However I see you have your Lipo alarm set to 3.5v (10.5v), does this mean these default settings in Naza are a little high? I'm flying with just the single standard battery at the moment.

    If so could you tell us what are your voltage settings for first and second level?

    Thanks :)
     
  5. lake_flyer

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    The Lipo alarm monitors the loaded voltage. I have my first level at 10.40 loaded which means 11.00 unloaded, I kept the loss at the default .60. Second level on 10.10 loaded or 10.70 unloaded. I don't go any lower. My batteries can keep enough juice to get charged again like this. Sometimes they take a longer time to balance out on the charger but so far, after 6 weeks and close to 100 flights they perform still fine.
     
  6. lake_flyer

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    One more thing for when you start experimenting with voltage levels:

    Lipos deplete linear until a certain point. Then it's getting very progressive. The lower voltages you set, the less time you get between the levels.
     
  7. biomedchad

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    i like these settings for everyone..i have osd so i can see actual mahs consumed during flight..so i have mine knocked down a tad bit lower..but for regular pilots these are great
     
  8. slothead

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    Let's complicate this just a little (maybe - I don't know). Suppose you are running aftermarket batteries with higher capacities than the DJI batt's. Do the settings still work the same way?
     
  9. biomedchad

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    yes..naza is going off of battery voltage not mahs..so a 3s is always going to be 12.4-12.6 Volts
     
  10. tobbe

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  11. lake_flyer

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    It connects to the balance connector of the battery. It is suitable for 2s-8s batteries and has 9 pins, one of which is the +. Since this we use a 3s battery we use only 4 pins (the + and 1,2 and 3). You just connect the balance connector to the first or the last 4 pins, depending on which side the + is.
     
  12. deltamike

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    Hi Tom,

    If a battery is 11.1 volts and is a 2200 mAh then an 11.1 volt at 7000 mAh will be suitable but for the physical size, but of course, they would last a dam sight longer than the 2200 mAh., and yes - the settings are the same regardless of the mAh.

    My aero engineer / electrical friend has a blog whose address is below. If you have any questions on ANYTHING electrical, then ask him. He is only too willing to help just ask.

    This guy has wired electrics on aircraft, is a pilot and engineer and only glad to help out.

    http://caravanchronicles.com/about/

    He is the engineer that created this chart

    [​IMG]


    Regards

    Pete
     
  13. twhphantom

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    Great Info!! Thanks for posting.
     
  14. deltamike

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    How about : - http://www.ebay.co.uk/itm/Digital-LCD-K ... 56638f1593

    Far more simple. I clip it to my shirt pocket.