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Minimum Cell Voltage

Discussion in 'Inspire 1 Help' started by AllanM, Apr 22, 2016.

  1. AllanM

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    I know there's a consensus of opinion here that TB47/48's shouldn't be discharged lower than 3.5 volts.
    This seem contrary to the general stuff I see on lipos elsewhere, where many seem to think that 3.3 is OK.
    Reason is, since last firmware you are given a red warning when the voltage falls below 3.5V and has made me very aware that often I'm dipping down to 3.4 at the end of flights. I've never worried about it until now.

    I'd be curious to know what the difference in chemistry is for the DJI lipos which makes < 3.5 a no go, and, it seems, just about every other lipo slightly less is acceptable.
    Is there anything from DJI about which documents this?
     
  2. Scotflieger

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    Starting with your last question first. There is no DJI documentation on the battery voltage or colour warnings.

    The Green/Amber/Red cell colourings are just an indication. The Red is indicating that one or more cells are nearing depletion and the user should be cautious and be thinking of landing. You will also see Amber and Red if you apply full power especially when the battery temperature is low (<20C). You should essential back off on your inputs.

    When doing the recommended 15-20 charge 100-0% resetting of the battery you can run the battery down to just under 3.5v before the motors cut. I then leave the aircraft powered up and come back when it has cut itself down. Apart from one battery with a weak cell (ground use only) I have not experienced any problems or concern.
     
    #2 Scotflieger, Apr 23, 2016
    Last edited: Apr 24, 2016
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  3. AllanM

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    Thanks for your reply Scotflieger.
    I use another lipo charger to slowly discharge the last 10% or so, when 'cycling', it reduces the load as the voltage drops. I'm not sure if that's really necessary now (with a bit more knowledge) as the DJI batteries cut well above 3V where damage would be inevitable.

    I'm really looking for a definitive answer as to whether running DJI batteries down to, say 3.4V under load towards the end of the flight is 'acceptable' as it is with other lipos. (Yes the limiter will kick in....)

    In fact, a year down the line of having the Inspire, I wish they just used normal lipos. I'd certainly rather scrap a lipo by over depletion than an inspire if thing went pear shaped.
     
  4. Scotflieger

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    The reset is supposed to completed without interruption from 100% to shutdown.
     
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  5. Nick H.

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    The auto shutoff from the battery circuitry is 3.0 volts. The first cell to hit 3.0 shuts off the battery. Happens the same whether the pack is flown or you plug it into a discharger. I've tested it many times and it happens the same way every time. I made my own discharger using car light bulbs and one of those cheap parallel charging boards meant to be used for a phantom or inspire. I find taking my packs to battery shut off tends to reset the, the best-all the way back to full capacity without needing to do the reset multiple times per battery.