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Batt. alarm

Discussion in 'General Discussion' started by sundance2013, Oct 30, 2013.

  1. sundance2013

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    Has anyone tried one of the audible batt. alarms you can buy that connect to the S2, S3, S4 connector on your batt.? Did it work? I got one but I get the red flashing LED and it lands before the audible alarm sounds.

    While on the subject, are the factory setting for the battery limits and warning OK or should I change them? Can I extend the flying time by raising the limits or should I leave them alone?

    It would seem there is battery life left if the audible alarm is not going off ...of course this may not be the case, it may just seems so.

    Thanks
     
  2. MrMediaGuy

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    Usually those little battery meter/alarms have a small microswitch you can press to toggle the alarm through a range of voltage settings. Does yours?

    On the Phantom, the default first-level alarm voltage under load is 10.7V, which is 3.57V per cell (rounded). So if you set your little alarm to 3.6V, it should go off just few seconds before the red light, assuming that your NAZA voltage sensor is well calibrated. (Yes, you can calibrate this in NAZA Assistant and it is sometimes the cause of the first-level alarm flashing too early when there is still plenty of capacity left in the pack.)

    The NAZA Assistant also has on the voltage tab a procedure for determining your voltage drop (loss) under load. The default is 0.6V, but if you have anything else added that pulls current or is heavy, you can bet your loss will be higher than the default. (Mine is 0.85V, with Zenmuse, 600mw VTX, and OSD.)

    That said, it's important to understand that whatever value you set for the loss doesn't really mean anything -- it's just a subtraction factor to get to the "under load" voltage. So you can always set loss to zero and just enter the *actual* value you want in the first box and NAZA Assistant will duplicate it in the last box. That will be the absolute voltage under load where each alarm will sound.

    The defaults in the NAZA are fairly conservative. Get a good voltmeter, and start reducing the alarm levels by 0.1V each flight. As soon as you get the red light, land and immediately pull the battery. Check the voltage. Keep lowering the alarm 0.1V each time until the recovery voltage of the battery when you check it is about 10.6V. That may mean a first-level alarm as low as 9.9V. Then get a good computer-controlled balance charger that shows the number of mAh charged back. Make sure you're not charging back more than 80% of the capacity of the pack (say 1750 mAh on the stock 2200 packs). Once you find the setting that gets you a recovery of about 10.6V and isn't overdischarging your packs, that's probably your maximum endurance.

    I went from getting barely 6:00 with gimbal, VTX and OSD, to more than 8:00 by carefully reducing the alarm settings -- with no harm to my packs.
     
  3. Gizmo3000

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    I haven't tried a Lipo alarm with my Phantom,. but did with my F450.

    I noticed that with my 450, it was capable of flying until the batteries were down to 3.3v.. which is when the little Lipo alarm goes off.
    But on my Phantom, when I check my batteries after flying, even after auto-land, they still register 3.6v or higher!
    ..so even if I had a battery alarm connected, it still wouldn't go off.
    which is likely what's happening to you as well.
     
  4. sundance2013

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    Thanks for the in depth info. The alarm I have is fixed.

    What is a good charger that allows me it monitor charging? All I have it
    the charger supplied with the Phantom.
     
  5. MrMediaGuy

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    Turnigy makes a number of good chargers; their Accucel 6 is a good entry-level if you only want to charge one pack at a time. Others will charge 4 or even 6 packs simultaneously. Be aware most chargers run on 12-18VDC so will require a separate power supply. On the bright side, you can power it from your car battery when you are "at the field." :)
     
  6. Gizmo3000

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    +1 for the Accucel6

    I use mine with a parallel charge board to charge up to 6 batteries at a time.

    I picked up mine, along with power supply, lipo bag and cell checker from hobbyking.
     
  7. Gizmo3000

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    So following up a bit on this thread,. I decided to change my battery failsafe a bit to see how it would influence things, and seemed to work.
    my first is 11.3 loss.6 10.70
    2nd is at 11.15 loss .6 loaded 10.55

    while testing it out, I'd fly around and land after the 2nd level kicked in and I had to give it just a bit too much juice to stay aloft.
    check the battery immediately after, and in many tests it staid it was at 3.73 per cell, (after it cooled down it would nudge up to 3.75 or so).
    But on one last battery run, I pushed it far,. it still didn't want to land itself, but when I tested the battery it said it was at 10.6! cells were down to like 3.4 when I tested it,. (eventually crept up to 3.6-3.7), did I push it too far?
    (it still hadn't self-landed, should it have?).

    ..I'm good with everything else in this hobby, but still grasping battery failsafe stuff!@#
     
  8. The Editor

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    To be honest - I would just turn the battery protection switch off altogether - it's more trouble than it's worth.
    I played around with the setting for the first couple of days when I got my Phantom just to see what it did etc. Then I turned it off and it has remained off ever since!
    I fly totally by timer as I have done for 20 years in the RC world. Touch wood I have NEVER had a crash due to battery dieing on me (although I have had my fair share of crashes for other reasons :shock: )

    The most important thing is the amount power you are putting back into your packs. Experiment with hovering and agressive flight and measure how much you are putting back into your lipo's using a decent quality charger. 1,760mAh is you 80% threshold (assuming a 2200mAh pack). If you are putting less than that back in that's fine.
    Give yourself a margin (I give myself around 50 seconds 'buffer time') before I get to the 1,760 mAh point.

    The trouble with that protection switch is it's unforgiving - If it's on, it will kick in at the set voltage and there is nothing you can do to stop it. I would rather trash a lipo pack and discharge it a little too much but get my Phantom back to me safely than watch as my aircraft descended into some woods or water because the protection switch said it's time to land !!
    Better to throw away a lipo than a Phantom :shock: